
Introduction
We've talked recently about the
roadmaps for high refresh rate displays and panels in the monitor market, spanning
across various panel technologies and screen sizes. One interesting sector was in
the TN Film market where high refresh rate screens of 120Hz and 144Hz have been
available for many years, originally being the only choice in the LCD monitor
market for high frame rate gaming. While other panel technologies like IPS and
VA have more recently ventured in to the 120Hz/144Hz refresh rate market
themselves, TN Film is again pushing the boundaries this year with the arrival
of native 240Hz refresh rate support. This doubles the potential frame rate
support from the original 120Hz panels from many years ago, going back to 2009
in fact. If you refer to the previously mentioned roadmap article you will see
that it is AU Optronics who, as a panel manufacturer, are pushing the refresh
rate for this new generation of TN Film panel, with options being produced in
24.5" and 27" sizes. The first to go in to production was the 24.5" panel
variants which have quickly been adopted by some of the main gaming display
manufacturers. Acer, Asus, BenQ and AOC have all got equivalent 24.5" models
(often referenced as 25" in size for ease) coming out to compete in the ever-popular
gamers sector.
We have already reviewed recently the AOC
offering, their
AGON AG251FZ which combined one of these new panels with support for AMD FreeSync
variable refresh rates and a whole range of gaming features. Now we have with us another option, produced by Asus and
this time paired with NVIDIA G-sync instead. The new PG258Q forms part of their
popular ROG Swift branded gaming range of screens, and this model also offers some
impressive gaming features of its own including the aforementioned 240Hz native refresh
rate, along with a 1ms G2G response time, G-sync and even ULMB (Ultra Low Motion
Blur) support which was not available on the AOC model. We will see how it compares to the AOC equivalent, as well as
against some of the other Asus gaming screens we've tested over the years.
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Specifications and Features
The following table gives detailed information
about the specs of the screen:
Monitor
Specifications |
Size |
24.5"WS |
Panel Coating |
Medium AG coating |
Aspect Ratio |
16:9 |
Interfaces |
1x DisplayPort
(version 1.2a), 1x HDMI 1.4
|
Resolution |
1920 x 1080 |
Pixel Pitch |
0.2825 mm |
Design
colour |
Matte black plastic bezel and stand with some
bronze coloured trim in places |
Response Time |
1ms G2G |
Ergonomics |
Tilt, 120mm height, swivel, rotate |
Static Contrast Ratio |
1000:1 |
Dynamic Contrast Ratio |
50 million:1 |
VESA Compatible |
Yes 100mm |
Brightness |
400 cd/m2 |
Accessories |
Power cable and brick, DisplayPort, HDMI,
USB cables |
Viewing Angles |
170 / 160 |
Panel Technology |
AU Optronics TN Film |
Weight |
with stand: 5.6 Kg |
Backlight Technology |
W-LED |
Physical Dimensions |
(WxHxD)
564.1 x 383.7 - 503.7 x 253.7 mm |
Colour Depth |
16.7m (6-bit + FRC) |
Refresh Rate |
240Hz native
G-sync range 30 - 240Hz |
Special
Features |
2x
USB 3.0 ports, G-sync, ULMB, ROG lighting system, headphone socket, NVIDIA
3D Vision |
Colour Gamut |
Standard gamut
sRGB, ~72% NTSC |
The PG258Q offers a limited range of connectivity
options given the use of a G-sync module, with only DisplayPort 1.2a and HDMI offered. DisplayPort
is needed to support the refresh rate up to 240Hz, including G-sync support from compatible
NVIDIA graphics cards (30- 240Hz range).
The digital interfaces are HDCP certified for encrypted content and the video
cables are provided in the box for both video connections.
The screen has an external power supply and comes
packaged with the power cable and power brick you need. There are also 2x USB 3.0 ports
available and a headphone socket on the back underside of the screen. There are
no further extras here such as integrated speakers, mic connections or light
sensors.
Below is a summary of the features and connections
of the screen:
Feature |
Yes / No |
Feature |
Yes / No |
Tilt adjust |
 |
DVI |
 |
Height adjust |
 |
HDMI |
 |
Swivel adjust |
 |
D-sub |
 |
Rotate adjust |
 |
DisplayPort |
 |
VESA compliant |
 |
Component |
 |
USB 2.0 Ports |
 |
Audio connection |
 |
USB 3.0 Ports |
 |
HDCP Support |
 |
Card Reader |
 |
MHL Support |
 |
Ambient Light Sensor |
 |
Integrated Speakers |
 |
Human Motion Sensor |
 |
PiP / PbP |
 |
Touch Screen |
 |
Blur Reduction Mode |
 |
Factory calibration |
 |
G-Sync |
 |
Hardware calibration |
 |
FreeSync |
 |
Uniformity correction |
 |
Wireless charging |
 |

Design and Ergonomics


Above: front views of the screen and stand. Click for larger versions
The ROG Swift PG258Q comes in a mostly black
design, with some copper coloured highlight sections on the base of the stand
and on the back where it attaches in to the screen. The black plastics are a
matte finish and the screen has a nice thin bezel around all four sides. The
total black border measures 9mm along the left/right hand sides, 10mm along the
top and about 14.5mm along the bottom edge. There is a shiny silver Asus logo in
the middle of the bottom bezel, and a light grey DisplayPort and HDMI logo in
the bottom left hand corner. The power LED is tucked under the bottom right hand
edge of the screen and is hard to see from a normal viewing position. This glows
white during screen operation and amber in standby.

Above: rear
views of the screen. Click for larger versions

Above: view
of the stand base. Click for larger versions
The back of the screen is finished with a matte
black plastic as well and the stand connects in to the VESA 100mm compliant
mounting section which has some copper coloured plastic trim. There is a red ROG
Swift branding logo on the back of the stand, which stands out a little and
perhaps could have been the same copper colour as the other highlights. The
stand provides a three-pronged metal base which offers a wide and sturdy base
for the screen. It remains very stable on the stand with very little wobble at
all. There's a cable tidy hole in the back of the stand as shown above. One
thing to note about the stand is that because of the shorter prong at the back,
you do need to have the display quite a long way forward from the back edge of
your desk. The front of the panel is about 230mm (23cm) from the back edge of
the desk if you line up the back of the stand exactly, so it's quite a long way
forward as a result. Make sure your desk is deep enough to accomodate.

Above:
rear view showing carry handle
and VESA mounting section. Click for larger version
The display has a nice thin side profile thanks to the use of a W-LED backlight unit and an external
power supply although as you can see from the images below, the stand is
quite chunky in design since it contains the 'light in motion' feature in the
bottom to project a logo on to your desk. It is at least very sturdy and solid. There is a full
range of ergonomic adjustments offered from the stand as well which is nice to
see.

Above: full
tilt range of the screen shown. Click for larger versions
Tilt is smooth but stiff
to use, although it does offer a pretty good range of adjustment as shown above.
We would have liked this to be a little less stiff really to operate.

Above: full
height adjustment range of the screen shown. Click for larger versions
Height adjustment is also available with
smooth and easy movement. At the
lowest setting the bottom edge of the screen is ~55mm from the top of the
desk, and at maximum extension it is ~175mm. This gives a total adjustment
range of ~120mm which is decent and as advertised.
Side to side swivel is smooth but quite
stiff to
use and offers a decent enough adjustment range. The rotation function is
quite smooth too but again quite stiff to operate, but is at least available for those
who might want to use it and somewhat practical on a screen this size.
A summary of the ergonomic adjustments
are shown below:
Function |
Range |
Smoothness |
Ease of Use |
Tilt |
Yes |
Smooth |
Stiff |
Height |
120mm |
Smooth |
Easy |
Swivel |
Yes |
Smooth |
Quite Stiff |
Rotate |
Yes |
Quite Smooth |
Quite Stiff |
Overall |
Full range of adjustments
but some are a little stiff to operate. Very sturdy stand and no wobble |
The materials were of a good standard and the
build quality felt very good as well. There was no audible noise from the screen,
even when conducting specific tests which can often identify buzzing issues.
The whole screen remained cool even during prolonged use as well which
was pleasing.


Above:
interface connections on the back. Click for larger versions
The back of the screen features the interface
connections as shown above. There are DisplayPort, HDMI, USB upstream, 2x USB
3.0 downstream, a service port (not useable), power connection and headphone
jack provided. Nice to see a couple of USB ports available although it would
have been even better if they'd been located on the edge of the screen for
easier access.

The base of the stand contains the Asus 'Light in
Motion' projection which is quite nice and looks smart. We don't like it as much
as the light system Acer have used on some of their Predator models where
there's a range of projected colours and options as opposed to just a small-ish
red logo projection.

OSD Menu

Above: OSD control buttons on the back right hand side of the screen. Click for larger
version

The OSD menu is controlled primarily by a small
joystick control located on the back of the screen, in the bottom right hand
corner. This joystick is accompanied by 3 pressable buttons as well as an on/off
power button. There are no markings on the front of the screen so you have to
operate this all by touch. There is quick access to the
GamePlus menu and the
GameVisual preset mode menu from two of the buttons as indicated above.


The OSD menu is split in to 5 sections down the
left hand side. The first menu offers 4 levels for the blue light filter. The
color menu contains the settings for brightness, contrast, colour temperature
and gamma which will be useful during
calibration.


The image menu has the control for the
overdrive
function (OD setting), as well as the dynamic contrast ratio, dark boost setting
for gaming, and the Ultra Low Motion Blur (ULMB) setting. Input selection and
system setup are pretty self explanatory. The 'light in motion' setting is in
the system setup menu for the light feature built in to the base of the stand.
Navigation was quick and easy thanks to the joystick control and it felt
intuitive navigating around the options. There's a decent range of options
available as well which was pleasing.

Power Consumption
In terms of power consumption the manufacturer
lists typical 'on' usage as <65W which they stats is "measuring a screen
brightness of 200 nits without audio/ USB/ Card reader connection". They also
list <0.5W usage in standby. We carried out our normal tests to
establish its power consumption ourselves.
 |
State and Brightness
Setting |
Manufacturer Spec (W) |
Measured Power Usage
(W) |
Default (80%) |
<65.0 |
26.6 |
Calibrated (1%) |
- |
17.5 |
Maximum Brightness (100%) |
- |
29.1 |
Minimum Brightness (0%) |
- |
17.4 |
Standby |
<0.5 |
0.5 |
|
We tested this ourselves and found that out of the
box the screen used 26.6W at the default 80% brightness setting. Once calibrated the screen reached
17.5W consumption, and in standby it
used only 0.5W. We have plotted these results below compared with other screens
we have tested. The consumption is comparable to the other
screens in this 24 - 25" size range we have tested as you might expect (comparing the calibrated states).


Panel and Backlighting
Panel Manufacturer |
AU Optronics |
Colour Palette |
16.7 million |
Panel Technology |
TN Film |
Colour Depth |
6-bit + FRC |
Panel Module |
Q250HTA00 |
Colour space |
Standard gamut |
Backlighting Type |
W-LED |
Colour space coverage (%) |
sRGB, ~72% NTSC |
Panel Part and Colour Depth
The screen features an
AU Optronics Q250HTA00 TN Film technology panel which is capable of producing
16.7 million colours. This is achieved through a 6-bit colour depth with
additional Frame Rate Control (FRC). The
panel part is confirmed when dismantling the screen as shown below. This is an
unusual designation for an AUO panel, which suggests it perhaps might be a
custom-made part for Asus:


Screen
Coating
The
screen coating is a medium anti-glare (AG) offering. It isn't a semi-glossy
coating, and isn't as light as some modern IPS type panels either. It's in
keeping with other TN Film panels we've tested. Thankfully it isn't a heavily
grainy coating like some old IPS panels feature, although there is some
graininess noticeable. It retains its anti-glare properties to avoid too many
unwanted reflections of a full glossy coating, but does not produce an too
grainy or dirty an image that some thicker AG coatings can. There were some
slight cross-hatching patterns visible on the coating as well but only if you
looked very closely.
Backlight Type and Colour Gamut
The screen uses a White-LED (W-LED) backlight unit
which is standard in today's market. This helps reduce power consumption
compared with older CCFL backlight units and brings about some environmental
benefits as well. The W-LED unit offers a standard colour gamut which is
approximately equal to the sRGB colour space. Anyone wanting to work with wider colour spaces would need to consider
wide gamut CCFL screens or the newer range of GB-r-LED type (and similar)
displays available now. If you want to read more about colour spaces and gamut
then please have a read of our
detailed article.
Backlight
Dimming and Flicker
We tested the screen to establish the methods used
to control backlight dimming. Our in depth article talks in more details about a
common method used for this which is called
Pulse Width Modulation (PWM). This in itself gives cause for concern to some
users who have experienced eye strain, headaches and other symptoms as a result
of the flickering backlight caused by this technology. We use a photosensor +
oscilloscope system to measure backlight dimming control
with a high level of accuracy and ease. These tests allow us to establish
1) Whether PWM is being used to control the
backlight
2) The frequency and other characteristics at which this operates, if it is used
3) Whether a flicker may be introduced or potentially noticeable at certain
settings
If PWM is used for backlight dimming, the higher
the frequency, the less likely you are to see artefacts and flicker. The duty
cycle (the time for which the backlight is on) is also important and the shorter
the duty cycle, the more potential there is that you may see flicker. The other
factor which can influence flicker is the amplitude of the PWM, measuring the
difference in brightness output between the 'on' and 'off' states. Please
remember that not every user would notice a flicker from a backlight using PWM,
but it is something to be wary of. It is also a hard thing to quantify as it is
very subjective when talking about whether a user may or may not experience the
side effects.
100% 50%
0%

Above scale = 1
horizontal grid = 5ms
At 100% brightness a constant voltage is applied
to the backlight. As you reduce the brightness setting to dim the backlight a
Direct Current (DC) method is used, as opposed to any form of PWM. This applies
to all brightness settings from 100% down to 0%. The screen is flicker free as a
result which is great news.
Pulse Width
Modulation Used |
No |
Cycling
Frequency |
n/a |
Possible
Flicker at |
|
100% Brightness |
No |
50% Brightness |
No |
0% Brightness |
No |

Contrast
Stability and Brightness
We wanted to see how much variance there was in
the screens contrast as we adjusted the monitor setting for brightness.
In theory, brightness and contrast are two independent parameters, and good
contrast is a requirement regardless of the brightness adjustment.
Unfortunately, such is not always the case in practice. We recorded the
screens luminance and black depth at various OSD brightness settings, and
calculated the contrast ratio from there. Graphics card settings were left at
default with no ICC profile or calibration active. Tests were made using an
X-rite i1 Display Pro colorimeter. It should be noted that we used the
BasICColor calibration software here to record these, and so luminance at
default settings may vary a little from the LaCie Blue Eye Pro report.
OSD
Brightness |
Luminance
(cd/m2) |
Black
Point (cd/m2) |
Contrast
Ratio
( x:1) |
100 |
487.63 |
0.49 |
995 |
90 |
452.23 |
0.45 |
1005 |
80 |
416.24 |
0.42 |
991 |
70 |
378.78 |
0.38 |
997 |
60 |
342.43 |
0.34 |
1007 |
50 |
306.40 |
0.31 |
988 |
40 |
269.80 |
0.27 |
999 |
30 |
231.20 |
0.23 |
1005 |
20 |
193.24 |
0.19 |
1017 |
10 |
155.03 |
0.16 |
969 |
0 |
116.24 |
0.12 |
969 |
Total Luminance Adjustment Range
(cd/m2) |
371.39 |
Brightness OSD setting controls backlight? |
 |
Total Black Point
Adjustment Range (cd/m2) |
0.37 |
Average Static Contrast Ratio |
995:1 |
PWM Free? |
 |
Recommended OSD setting
for 120 cd/m2 |
1 |
We conducted these tests in the default settings. The brightness control gave us a
very good range of adjustment, although there was a limitation at the lower end
certainly. At the top end the maximum luminance reached 488
cd/m2 which was
a lot higher than the specified maximum brightness of 400 cd/m2
from the manufacturer. There was a good 371 cd/m2 adjustment range in
total, and so at the minimum setting you could reach down to luminance of only
116 cd/m2. This is still very high really and while it should be an adequate
level for typical day to day work, it doesn't give you any option for those
wanting to work in darkened room conditions with low ambient light. A setting of
1% in the OSD menu should return you a
luminance of around 120 cd/m2 at default settings in this preset mode.
It should be noted that the
brightness regulation is controlled without the need for
Pulse Width Modulation, using a Direct Current (DC) method for all
brightness settings between 100 and 0% and so the screen is flicker free.

We have plotted the
luminance trend on the graph above. The screen behaves as it should in this
regard, with a reduction in the luminance output of the screen controlled by the
reduction in the OSD brightness setting. This is a linear relationship as shown.

The average contrast ratio of
the screen was good for a TN Film panel at 995:1. This was very stable
across the brightness adjustment range as shown above. Note that this was in the
default screen settings.

Testing
Methodology

An
important thing to consider for most users is how a screen will perform out of
the box and with some basic manual adjustments. Since most users won't have
access to hardware colorimeter tools, it is important to understand how the
screen is going to perform in terms of colour accuracy for the average user.
We restored our graphics card to default settings
and disabled any previously active ICC profiles and gamma corrections. The
screen was tested at default factory settings using our new
X-rite i1
Pro 2 Spectrophotometer combined with
LaCie's Blue Eye Pro software suite. An X-rite i1 Display Pro colorimeter was
also used to verify the black point and contrast ratio since the i1 Pro 2
spectrophotometer is less
reliable at the darker end.
Targets for these tests are as follows:
-
CIE Diagram - validates the colour space
covered by the monitors backlighting in a 2D view, with the black triangle representing the
displays gamut, and other reference colour spaces shown for comparison
-
Gamma - we aim for 2.2 which is the default
for computer monitors
-
Colour temperature / white point - we aim
for 6500k which is the temperature of daylight
-
Luminance - we aim for 120
cd/m2, which is
the recommended luminance for LCD monitors in normal lighting conditions
-
Black depth - we aim
for as low as possible to maximise shadow detail and to offer us the best
contrast ratio
-
Contrast ratio - we aim
for as high as possible. Any dynamic contrast ratio controls are turned off here
if present
-
dE average / maximum -
as low as possible.
If DeltaE >3, the color displayed is significantly different from the
theoretical one, meaning that the difference will be perceptible to the
viewer.
If DeltaE <2, LaCie considers the calibration a success; there remains a
slight difference, but it is barely undetectable.
If DeltaE < 1, the color fidelity is excellent.

Default Performance and
Setup
Default settings of the screen were as follows:
Monitor OSD Option |
Default Settings |
Game Visual preset mode |
Racing Mode |
Brightness |
80 |
Contrast |
50 |
Gamma |
2.2 |
Color Temp |
User Mode |
RGB |
100, 100, 100 |

Asus ROG Swift PG258Q - Default Settings



|
Default Settings |
luminance (cd/m2) |
437 |
Black Point (cd/m2) |
0.44 |
Contrast Ratio |
990:1 |
Initially out of the box the screen was set in the
default Racing Mode Game Visual preset and with the gamma option set to 2.2. With a very high
default 80% brightness setting out of the box the screen was overly bright and
uncomfortable to use, so you will definitely need to turn that down. You could
tell the screen was using a standard gamut backlight as well with the naked eye,
and the colour balance and temperature felt pretty good, although the image did
appear a little washed out and perhaps a little too cool.
We went
ahead and measured the default state with the i1 Pro 2. The
CIE diagram on the left of the image confirms that the monitors colour gamut
(black triangle) is fairly equal to
the sRGB colour space. There is some modest over-coverage in blues and greens but not by
anything significant. Default gamma was recorded at 2.0 average in this
mode, leaving it with a moderate 10% deviance
from the target. Remember this is a gaming screen,
where a lower gamma like this is often desirable for gaming uses. There are a
couple of other gamma settings in the OSD menu which affords you some further
control. We measured those modes as well and found that the 1.8 setting
delivered an average gamma of 1.6 (27% deviance from the target), while the 2.4
mode returned an average of 2.3 and only a small 3% deviance from the target. We
will look at some optimal settings in a moment. White
point was measured at a slightly cool 6121k, being 6%
out from the 6500k we'd ideally want for desktop use.
Luminance was recorded at an extremely bright 437
cd/m2 which is
far too high for prolonged general use. The screen was set at a default 80%
brightness in the OSD menu but that is easy to change of course to reach a more
comfortable setting without impacting any other aspect of the setup. The black
depth was 0.44 cd/m2 at this default
brightness setting, giving us a decent (for a TN Film panel) static contrast ratio of
990:1.
Colour accuracy was moderate out of the box
with an average dE of 3.0 measured. Testing the screen with colour
gradients showed smooth transitions in all shades, with some slight gradation evident
in darker tones.
Monitor OSD Option |
Optimal OSD Settings |
Game Visual preset mode |
Racing Mode |
Brightness |
1 |
Contrast |
50 |
Gamma |
2.4 |
Color Temp |
User Mode |
RGB |
93, 97, 100 |

Asus ROG Swift PG258Q -
Optimal OSD Settings


|
Optimal OSD Settings |
luminance (cd/m2) |
118 |
Black Point (cd/m2) |
0.13 |
Contrast Ratio |
892:1 |
We thought it might be useful to provide some
recommended OSD settings for the screen to show what is possible even without a
calibration device and proper ICC profiling of the display. A simple change in the OSD menu to gamma mode
2.4
returned a better setup for gamma, reducing the 10% deviance we'd seen out of
the box to only 5% now. The adjustments to the RGB controls brought the white
point in line, now at 6519k with 0% deviance from our target. You need to adjust
the brightness control all the way down to 1% to achieve a lower, more
comfortable luminance. The contrast ratio is impacted a little by the change to
the gamma mode, and the lowering of the RGB controls. It was now measured at
892:1 which was still decent enough for this panel technology.

Calibration
We used the
X-rite i1 Pro 2
Spectrophotometer combined with the LaCie Blue Eye Pro software package to
achieve these results and reports. An X-rite i1 Display Pro colorimeter was used
to validate the black depth and contrast ratios due to lower end limitations of
the i1 Pro device.
Monitor OSD Option |
Calibrated Settings |
Game Visual preset mode |
Racing Mode |
Brightness |
1 |
Contrast |
50 |
Gamma |
2.4 |
Color Temp |
User Mode |
RGB |
93, 97, 100 |

Asus ROG Swift PG258Q - Calibrated Settings

|
Calibrated Settings |
luminance (cd/m2) |
118 |
Black Point (cd/m2) |
0.137 |
Contrast Ratio |
859:1 |
We stuck to the optimal OSD settings we'd
identified before, including the 2.4 gamma mode and the slightly tweaked RGB
values. All these OSD
changes allowed us to obtain an optimal hardware starting point and setup before software level changes would be
made at the graphics card level. We left the LaCie software to calibrate
to "max" brightness which would just retain the luminance of whatever brightness
we'd set the screen to, and would not in any way try and alter the luminance at
the graphics card level, which can reduce contrast ratio. These adjustments
before profiling the screen would help preserve tonal values and limit
banding issues. After this we let the software carry out the LUT adjustments and create an
ICC profile.
Average gamma was now corrected to 2.2 average
with a 0% deviance, correcting the minor 5% deviance we'd seen out of the box in
this gamma mode 2.4. The
white point had now been corrected to 6480k, which corrected the 6% deviance
we'd seen out of the box. Luminance had been improved thanks to the adjustment
to the brightness control and was now being measured at 118
cd/m2. This
left us a black depth of 0.137 cd/m2 and maintained a fairly decent static
contrast ratio (for a TN Film panel) of 859:1. Colour accuracy of the resulting
profile was excellent, with dE average of 0.5 and maximum of 1.2. LaCie would
consider colour fidelity to be very good overall.
Testing the screen with various colour gradients
showed smooth transitions with only some slight gradation in darker tones. No
banding had been introduced which was pleasing.
You can use our settings and
try our calibrated ICC profile if you wish, which are available in
our ICC profile database. Keep in mind that results will vary from one
screen to another and from one computer / graphics card to another.

Calibration Performance Comparisons

The comparisons made in this section try to give
you a better view of how each screen performs, particularly out of the box which
is what is going to matter to most consumers. When comparing the default factory
settings for each monitor it is important to take into account several
measurement areas - gamma, white point and colour accuracy. There's no point
having a low dE colour accuracy figure if the gamma curve is way off for
instance. A good factory calibration requires all 3 to be well set up. We have
deliberately not included luminance in this comparison since this is normally
far too high by default on every screen. However, that is very easily controlled
through the brightness setting (on most screens) and should not impact the other
areas being measured anyway. It is easy enough to obtain a suitable luminance
for your working conditions and individual preferences, but a reliable factory
setup in gamma, white point and colour accuracy is important and not as easy to
change accurately without a calibration tool.
From these comparisons we can also compare the
calibrated colour accuracy, black depth and contrast ratio. After a calibration
the gamma, white point and luminance should all be at their desired targets.

Default setup of the screen out of the box was
moderate, with a gamma curve that was slightly too low (2.0 average, 10%
deviance from our target) and a slightly too cool white point (6121k, 6% out).
The screen is aimed at gaming and so this low gamma and cooler white point are
not uncommon, and often desirable for gaming uses anyway. It's very common for the
TN Film gaming screens to be set up out of the box with a lower gamma, and you
can see this if you look at the
Acer Predator XG270HU (1.8),
Asus MG248Q (1.9) and
BenQ XL2730Z (1.9) for example. Thankfully a few simple OSD changes can
deliver a setup more suitable for day to day use so we don't need to penalise the
screen here for its gaming gamma curve at default settings.


The display was pretty good when it came to static
contrast ratio for a TN Film panel, at 859:1 after calibration. This was a tad
lower than some other high end gaming TN Film screens like the competing
AOC AGON AG251FZ (931:1) and other displays like the Asus MG248Q (1005:1) and
BenQ XL2730Z (917:1) for instance. Of course
none of these TN Film panels can compete with VA panel types which can reach over 2000:1 easily, and
commonly up to 3000:1 (e.g.
Acer Predator Z35)
or even near 5000:1 (Eizo
Foris FG2421).
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Viewing Angles

Above: Viewing
angles shown from front and side, and from above and below. Click for
larger image
Viewing angles of the screen were as you might
expect from a TN Film panel. Unfortunately this panel technology is inherently
poor in this field, and so viewing angles are more restrictive than other
competing technologies like IPS and VA variants. Although the manufacturer will
quote a viewing angle of 170 / 160 (a classic indication that a TN Film panel is
being used by the way if in doubt), in practice there are some obvious contrast
and colour tone shifts horizontally, and especially vertically.
As you move your head from side to side in a
horizontal plane, there is a contrast shift and the image becomes more pale and
introduces a yellow hue. As you move to a wider angle the image can become more
washed out as well and a slight pink hue is introduced. Vertically the fields of
view are more restrictive still. From above the image becomes pale and washed
out, while from below there is a characteristic TN Film darkening of the image.
Unfortunately vertically the viewing angles will introduce noticeable shifts in
the contrast and colour tone of the image which mean that for any colour
critical work it is not really very well suited. TN Film panels have long
suffered from these restrictive viewing angles due to the nature of their pixel
structure. They are still fine for a single user for general use and certainly
the TN Film panels offer their advantages when it comes to
pixel response
times and refresh rate for gaming. If however, you were hoping to do any
colour critical or photography work you may find these shifts in the appearance
of the image difficult. An IPS-type panel would probably be a wiser choice if
you were looking for a screen with much wider viewing angles but having said
that you are probably mainly interested in gaming if you are considering this
screen. Remember, this screen is specifically designed for gaming, and so you
will have to live with some of the sacrifices of TN Film to get the kind of
gaming performance and features offered here. There are some high refresh rate
gaming IPS panels available now in larger sizes as well which can offer better
viewing angles than TN Film models, although they are normally priced higher and
have some other characteristic differences, and so TN Film models like this
still have their place for many users.

Above: View of an
all black screen from the side. Click for larger version
On a black image there is a slight pale grey
tint introduced to the image when viewed from a wide angle. This isn't too
severe and shouldn't present any real problems in practice. Certainly not the
obvious white glow you get from most modern IPS-type panels in similar
situations and fairly standard for a TN Film panel. Very similar to what we have
seen from other recent gaming TN Film screens like the
AOC AGON AG251FZ,
Asus MG248Q,
Asus ROG Swift PG278Q and
BenQ XL2730Z. The glow you see from most modern IPS panels can put off some
users. So on the one hand, those IPS models have much better general viewing
angles than the TN Film models, but they do show more glow which some people
find an issue.

Panel Uniformity
We wanted to test
here how uniform the brightness was across the screen, as well as identify any
leakage from the backlight in dark lighting conditions. Measurements of the
luminance were taken at 36 points across the panel on a pure white background.
The measurements for luminance were taken using BasICColor's calibration
software package, combined with an X-rite i1 Display Pro colorimeter with a
central point on the screen calibrated to 120 cd/m2. The below
uniformity diagram shows the difference, as a percentage, between the
measurement recorded at each point on the screen, as compared with the central
reference point.
It is worth
noting that panel uniformity can vary from one screen to another, and can depend
on manufacturing lines, screen transport and other local factors. This is only a
guide of the uniformity of the sample screen we have for review.

Uniformity of Luminance

The luminance uniformity of the screen was
pretty good overall. The screen showed a
dip in luminance towards the left hand edge, where in the worst case it
dropped to 97
cd/m2
(-24% deviance). 80% of the screen was within a 10% deviance from the
centrally calibrated point which was decent.

Backlight Leakage

Above: All black screen in a darkened room. Click for larger version
We also tested the screen with an all black image
and in a darkened room. A camera was used to capture the result. The camera
showed there was no real backlight bleed evident, but a little clouding along
the lower right hand edge of the screen. Nothing that should be noticeable in
day to day use.
Note: if you want to test your own screen for
backlight bleed and uniformity problems at any point you need to ensure you have
suitable testing conditions. Set the monitor to a sensible day to day brightness
level, preferably as close to 120
cd/m2 as you can get it (our tests are
once the screen is calibrated to this luminance). Don't just take a photo at the
default brightness which is almost always far too high and not a realistic usage
condition. You need to take the photo from about 1.5 - 2m back to avoid
capturing viewing angle characteristics, especially on IPS-type panels where
off-angle glow can come in to play easily. Photos should be taken in a darkened
room at a shutter speed which captures what you see reliably and doesn't
over-expose the image. A shutter speed of 1/8 second will probably be suitable
for this.

General and Office Applications
With a 1920 x 1080 resolution, the desktop real
estate of the PG258Q feels a step down compared with all the high resolution
panels we've tested, and the 27" 2560 x 1440 models we are used to using day to
day. You do lose a large amount of desktop space, and although side by side
split screen working is possible, it's not as easy due to the more limited
resolution and space. With a 0.2825mm pixel pitch, text is comfortable and easy
to read natively, providing a sharp and crisp image. It is not as sharp as the
1440p panels we've become accustomed to, or of course any ultra HD/4K
resolutions where scaling is used, but it is perfectly adequate. For this size
screen, 1920 x 1080 is about your limit of sensible resolution without needing
to use operating system scaling options.
The moderate AG coating of the TN Film panel could
be considered a bit grainy, especially on white office backgrounds to a lot of
people. It's not as clear as modern IPS coatings or any semi-glossy solution.
Still, it's not as grainy as old IPS panels and is on par with other TN Film
matrices we've tested. Perhaps the main issue with this panel technology though
is the restrictive viewing angles, making contrast and colour tone shifts a bit
of a problem when it comes to colour critical work. They are the same here as
other TN Film panels, being restrictive especially vertically. The screen is
fine when viewed head on though really for office and text work, but for colour
critical work or photo editing etc you'd be better off with an IPS-type panel.
The default setup of the screen was a little restrictive for normal uses, as the
gamma is set up more for gaming, but thankfully this was very easy to adjust
without a calibration tool via a simple change in the OSD menu. That provided a
good default setup then for day to day office work, once you've turned the
brightness setting down a long way. There are 4 blue light filter modes offered in the menu if you want to add further eye care protection and
might be worth experimenting with for prolonged office use or text reading.
The range of brightness
adjustment of the screen was very good, with the ability to offer a
luminance between 488 and 116 cd/m2. However, the adjustment
potential at the lower end was limited and that means that it might be hard to
use the screen in darker room conditions where there is a lower ambient light.
That's certainly a limitation of the backlight adjustment on the PG258Q here. A
setting of 1% in the OSD brightness control should return you a luminance close to 120
cd/m2 out of the box. On a more positive note, the brightness regulation is
controlled without the need for the use of the now infamous
Pulse-Width Modulation (PWM), and so those who suffer from eye fatigue or
headaches associated with flickering backlights need not worry. There was no
audible noise or buzzing from the screen, even when specifically looking for it
using test images with a large amount of text at once. The screen also remains
cool even during prolonged use.
There are a
couple of extra features on this screen for office environments, even though it's
primarily a gaming screen. There are 2x USB 3.0 ports although both are on the back
of the screen so not easy access like on some other displays. There's also a
headphone connection but no integrated speakers. There is no
ambient light sensor, card reader, motion sensor or anything else provided which
can sometimes be useful in office environments.
There was a good range of ergonomic adjustments
available from the stand allowing you to obtain a comfortable position for a
wide variety of angles although some were quite stiff to operate. The VESA mounting support may also be useful to some
people as well.

Responsiveness and Gaming
The ROG Swift PG258Q is firmly a gamers screen, with key
features including the native 240Hz refresh rate, 1ms G2G response time and
support for NVIDIA G-sync and ULMB. You will need to keep in mind the demands on your
system and graphics card to power a screen like this, as there's quite a drain
on resources to run at 240Hz! The resolution is 'only' 1920 x 1080 so that is at
least a bit easier than if this was a 1440p or 4k resolution screen. For systems
which can't manage the 240Hz reliably or frequently, G-sync is supported for
variable refresh rate control, helping to eliminate tearing and stuttering and
operating in a nice wide range from 30 to 240Hz. Asus
have provided a wide range of
additional extras for gaming that we will talk about in a moment.
Quoted G2G Response Time |
1ms G2G |
Quoted ISO Response Time |
n/a |
Panel Manufacturer and
Technology |
AU Optronics TN Film |
Panel Part |
Q250HTA00 |
Overdrive Used |
Yes |
Overdrive Control Available to
User |
Overdrive |
Overdrive Settings |
Off, Normal, Extreme |
The ROG Swift PG258Q is rated by Asus as having a 1ms G2G
response time which indicate the panel uses
overdrive /
response time compensation (RTC) technology to boost pixel transitions
across grey to grey changes. The
part
being used is the
AU Optronics Q250HTA00 TN Film technology panel. Have a read about response time in
our
specs section if you need additional information about this measurement. As
a reminder, this is only the second native 240Hz refresh rate panel of any size and
type we have seen having recently reviewed the equivalent AOC model, the
AGON AG251FZ.

We will first test the screen using our thorough
response time testing method. This uses an oscilloscope and photosensor to
measure the pixel response times across a series of different transitions, in
the full range from 0 (black) to 255 (white). This will give us a realistic view
of how the monitor performs in real life, as opposed to being reliant only on a
manufacturers spec. We can work out the response times for changing between many
different shades, calculate the maximum, minimum and average grey
to grey (G2G) response times, and provide an evaluation of any overshoot present
on the monitor.
We use an
ETC M526
oscilloscope for these measurements along with a custom photosensor device.
Have a read of
our response time measurement article for a full explanation of the testing methodology and reported
data.

Overdrive Setting

The 'OD' overdrive control is available via the 'image' section of the OSD menu as shown above. We will test all
three modes to
see which is optimal first of all. For now we have taken these measurements at the maximum 240Hz refresh rate, but we will look at the
implications of the refresh rate in a moment once we've
established the behaviour of the response times under this setting.



In the 'off' setting the response times were
mixed, with some around the advertised 1ms G2G figure, but many being much
slower up around 9 - 13ms. This gave us an average figure of 7.1ms and while there was no overshoot as you would expect with
overdrive turned off, but the response times were slower than we would like from
a TN Film panel. Turning the OD setting up to 'normal' brought about decent and
noticeable improvements, with an average response time now measured at 2.9ms.
Some moderate overshoot started to appear in a couple of transitions here, but
this mode was certainly faster and more fluid than the 'off' setting. If you
push the OD setting up to the maximum 'extreme' level then there's no real
improvements to response times overall but the overshoot becomes far more
noticeable and pronounced. Stick with the 'normal' mode.

Refresh Rate and G-sync

The PG258Q supports a refresh rate of up to 240Hz
natively, and as we've discussed earlier this is one of the first panels supporting such
a high refresh rate on the market. You can quickly and easily select this
refresh rate in Windows as shown above, although we did find we had to use the
provided DisplayPort cable rather than our regular day to day cable, so perhaps
it is a little fussy on the cabling choice. Just stick with the one provided in
the box and
you will be fine. When enabled, and from a compatible system, G-sync is also
available which operates in a range between 30 and 240Hz. There are
improvements in perceived motion clarity as you increase the refresh rate, and
the 240Hz certainly feels more fluid and faster than 120 / 144Hz. The
improvement is not as noticeable as when you move from 60 to 120/144Hz for the first
time, but the ability to deliver even higher frame rates from 144 - 240Hz is
certainly welcome. From an NVIDIA test system we found stable performance without any
frames being dropped at all refresh rates from 60Hz to 240Hz which was good
news.
Refresh Rate Impact, Overdrive Mode = Normal
We stuck to the 'normal' overdrive setting for now
and we wanted to test the response times at a range of refresh rates to see if
that influences the pixel transitions. It's quite common for the overdrive
impulse to be dynamically controlled across a wide refresh rate range like this.
The overshoot can also be impacted we have seen in the past.



As you can see from these measurements the actual
pixel transition times vary a little as you increase the refresh rate. at 60Hz
the overdrive impulse seemed to be a little more modest, resulting in a 4.9ms
G2G response time and no overshoot being measured. If you increase the refresh
rate up to 144Hz, the response times are improved a little to help ensure the
pixel transitions can keep up with the frame rate demands. At 144Hz, the
response times need to be reliably under 6.94ms average to avoid additional smearing and
blurring being introduced, and so the boost in the overdrive impulse helps
achieve that nicely. The response times are pushed a little more by the time you
reach 240Hz where they need to be <4.16ms and again this is largely achieved.
Only moderate levels of overshoot start to appear at these higher refresh rates
as well which was pleasing. This 'normal' OD mode is capable of handling the
full refresh rate range nicely, so you can stick with this for all your refresh
rate settings, including when G-sync is dynamically controlling it for you.

Detailed Response Time Measurements
Refresh
Rate = 240Hz, Overdrive = Normal
 

We stuck with the optimal 'normal'
response time setting at the maximum 240Hz refresh rate. The
average G2G response time was measured at 3.4ms which was very good and
represented very fast pixel transition times from this new TN Film panel. Some
transitions reached basically as low as the advertised 1ms G2G as well. There
were a few transitions which were a little slower than the required 4.16ms
figure to maintain a 240Hz frame rate but overall the response times were very
good here.


If we evaluate the Response Time Compensation
(RTC) overshoot then the results show very little overshoot overall, with only a
couple of transitions really showing anything at all, and even then at only
moderate levels. In this normal OD mode the overshoot was minimal which was
excellent news and actually very rare for a fast TN Film panel. They typically
have higher levels of overshoot than seen here so Asus have done a nice job
keeping it under control.

Display Comparisons


The above comparison table and graph shows you the
lowest, average and highest G2G response time measurement for each screen we
have tested with our oscilloscope system. There is also a colour coded mark next
to each screen in the table to indicate the RTC overshoot error, as the response
time figure alone doesn't tell the whole story.
As a reminder, these figures are at 240Hz refresh
rate and with overdrive set to 'normal'. The response time performance of the
PG258Q was very impressive overall, with some of the fastest TN Film response
times we've seen, while still keeping overshoot at a low level. A few other
models such as the AOC AGON AG251FZ reached a little lower at 2.6ms G2G but with
moderately high levels of overshoot then apparent. We would rather have the
slightly "slower" (3.4ms G2G isn't slow!) response times here to be honest with
lower overshoot, so we were impressed with the PG258Q's performance. The G-sync
module did a nice job of dynamically controlling the response times across a
wide refresh rate range as well, making it easy to stick with one OD setting and
have excellent performance across the range.

Ultra Low Motion Blur (ULMB)

The PG258Q also features an integrated Blur
Reduction Backlight system, dubbed "Ultra Low Motion Blur" (ULMB) by
NVIDIA.
This is linked to the G-sync module and is provided on most G-sync enabled
screens that have a native high refresh rate. We have
already seen a lot of positive improvements in perceived motion blur from such
systems in the past. Our
in depth article from June 2013
(updated 17 March 2015) looked at this in a lot
more detail, and tested some of the original LightBoost "hacks" to achieve a
strobed backlight and blur reduction benefits. Since then we've seen a quite a
lot of
monitors integrate a strobed backlight with simple user control from the
menu and with better implementation than LightBoost methods.
The ULMB feature is accessible from the 'image'
section of the OSD menu. It is only available when running the
screen at 100, 120 and 144Hz modes. It is not available at 200Hz or 240Hz sadly, and it is also important to note that ULMB does not
work when you are using G-sync, it's one or the other. When you enable the ULMB
feature a new option appears for the "ULMB Pulse Width" which allows you to
control the duration of the backlight strobes. A shorter "on" period can help
reduce perceived motion blur even more, but at the cost of screen brightness. You can adjust this between 100 and 10, and as you lower the setting
the screen also becomes progressively darker as you reduce the "on" period of
the strobe. Nice to see this included as an option within the menu for those who
like to play around with the setting, much like you could do by adjusting LightBoost levels on older models using the
"hack" method. There is no control to adjust the timing of the strobe to
impact the strobe cross-talk it can introduce, so we will have to hope that the default
timing setup is suitable. We will look at that in a moment.
Operation - 100Hz

ULMB
backlight cycling, 100Hz
(scale = 5ms)
pulse width setting= 100
We measured the screen using our oscilloscope when
viewing a solid white image, with ULMB feature turned on and with
refresh rate set at 100Hz. This is the lowest refresh rate at which you can
operate the ULMB mode. As a reminder, it works at 100, 120 and 144Hz only. We
left the pulse width (strobe length) setting at 100 initially. Normally the oscillograph would show a flat straight
line when measuring a static white image (as no PWM is being used for backlight
dimming), but here the ULMB feature is cycling the backlight off and
on rapidly.
The time for each complete cycle is 10ms which
shows that in this case the backlight is being cycled at the same frequency as
the refresh rate, 100 times per second. The strobe is in time with the refresh
rate of 100Hz.
Operation - 120Hz

ULMB
backlight cycling, 120Hz
(scale = 5ms)
pulse width setting = 100
When running the screen at a 120Hz refresh rate
the behaviour is exactly the same. The only difference is that the strobe is now
synced with the new refresh rate, with a new strobe every 8.33ms (120 times per
second).
Operation - 144Hz

ULMB
backlight cycling, 144Hz
(scale = 5ms)
pulse width setting = 100
Again when set at 144Hz refresh rate the strobes
are in sync again, with a new strobe every 6.94ms (144 times per second). The
above is with pulse width at the default 100. We can also see what impact on the
strobing it has if you lower the pulse width setting.

ULMB
backlight cycling, 144Hz
(scale = 5ms)
pulse width setting = 50

ULMB
backlight cycling, 144Hz
(scale = 5ms)
pulse width setting = 10
As you reduce the pulse width setting you are
adjusting the 'on' period of the strobe, shown by the top portion of each peak. As you reduce the setting the strobe
'on' time gets progressively shorter as you can see from the above 2 graphs, the
first at a setting of 50 and the second at a setting of 10 (the minimum setting
available). This impacts the perceived blur somewhat, with the shorter 'on'
times resulting in a clearer image. At the same time though the brightness of
the image is affected and it becomes very dark, the lower you go with the
setting. More on that in a moment. There will be a point where the user does not
see any further benefit to their eyes of reducing the strobe length further, but
you can have a play around with the setting to find your personal preference to
balance perceived motion blur and brightness of the image.
Pulse Width Setting - Strobe Length
We measured the strobe length at a variety of the
Pulse Width settings, while running at the maximum 144Hz refresh rate mode. You
can adjust the setting in steps of 1 incidentally. Each complete strobe lasts a
total of 6.94ms (144 strobes per second).
Pulse Width
Setting |
On period (ms) |
100 |
1.625 |
75 |
1.250 |
50 |
0.750 |
25 |
0.375 |
10 (min) |
0.250 |
Pulse Width Setting - Brightness Range (144Hz)
Pulse Width
Setting |
Luminance
(cd/m2) |
Black
Point (cd/m2) |
Contrast
Ratio
( x:1) |
100 |
274.91 |
0.33 |
833 |
75 |
210.55 |
0.25 |
842 |
50 |
139.69 |
0.17 |
822 |
25 |
72.07 |
0.09 |
801 |
10 (min) |
29.27 |
0.03 |
976 |
We tested the brightness output of the screen when
ULMB was turned on at 144Hz. You can independently control the brightness setting as well
if you want, but we left it at the default 100 and just changed the pulse width
(PW) strobe length setting to establish the brightness range when using this
option. With the PW setting at 100 the maximum achievable luminance of the
screen was a very good 275
cd/m2. This
should be plenty for most uses, but you cannot get a brighter display when
using ULMB if you wanted to. This is a very strong performance from a strobe
backlight though.
You can achieve a slightly brighter display if you
use the feature at 100 or 120Hz since the strobes are less frequent, but it's not
a significant amount.
As you reduce
the PW setting the luminance drops significantly, at the lowest setting probably
being far too dark for any practical use. At least you can control a reasonably
wide range here, so you can find a level which suits your needs. We suspect a
PW setting of 100 will probably be perfectly adequate for most normal users anyway, as the
ULMB mode certainly brings about positive improvements to the perceived motion
blur. If you want to lower the brightness output of the screen, reducing the
pulse width setting is probably a better option than simply lowering the
brightness control, as it should bring about some minor blur reduction benefits
as well.
Brightness Range (PW at 100, 144Hz)
Brightness Setting |
Luminance
(cd/m2) |
Black
Point (cd/m2) |
Contrast
Ratio
( x:1) |
100 |
274.91 |
0.33 |
833 |
75 |
224.40 |
0.27 |
831 |
50 |
160.00 |
0.19 |
842 |
25 |
93.60 |
0.11 |
851 |
0 |
21.67 |
0.03 |
722 |
We also wanted to test the brightness range when
leaving PW at its default 100, and changing the brightness control of the screen
instead. This leaves the strobe behaviour alone, operating as it does with PW at
100, and instead just dims the backlight. The table above confirms the range
available through that control. You can achieve a slightly brighter display if
you use the feature at 100 or
120Hz since the strobes are less frequent, but it's not a significant amount.
Thankfully the brightness setting when ULMB is
turned on is independent to when ULMB is off, and it remembers your last setting
as well (or at least it seemed to most of the time). So you can have the brightness down at 1% for normal desktop use (as
per our calibration section) to achieve a comfortable brightness, and then have
it at a completely different saved setting when you enable ULMB. This is great
news as at 1% brightness the luminance with ULMB on is far too low. you will
want to bump it up when you're using ULMB and thankfully there's a great range
available and a very bright upper limit if you need it. That's rare for a
strobed backlight system, and so we were impressed with the way it's been
implemented on the PG258Q.
Maximum Blur Reduction Brightness - Display
Comparison
For ease of reference we have
also provided a comparison table below of all the blur reduction enabled
displays we've tested, showing their maximum luminance before blur reduction is
turned on (normal mode) and their maximum luminance with the feature enabled.
This will give you an idea of the maximum brightness you can expect from each
model when using their blur reduction feature, if that is important to you. A
lot of people want a brighter display for gaming and sometimes the relatively
low maximum luminance from blur reduction modes is a limitation.
These comparisons are with the refresh rate as
high as is available for the blur reduction feature to function. For most this
is at 120Hz, but some also support the feature at higher. You can achieve a
slightly brighter display if you use the feature at 85 or 100Hz since the
strobes are less frequent, but it's not a significant amount. That can also
introduce more visible flicker in some situations.
Model |
Refresh Rate |
Max Normal
Luminance
Blur Reduction Off
(cd/m2) |
Max Luminance
Blur Reduction On
(cd/m2) |
Acer XB270HU* |
100Hz* |
327 |
111 |
Acer Predator Z35 |
120Hz |
359 |
111 |
Asus ROG Swift PG258Q |
144Hz |
488 |
275 |
Asus ROG Swift PG278Q |
120Hz |
385 |
123 |
Asus ROG Swift PG279Q |
120Hz |
331 |
101 |
BenQ XL2720Z |
144Hz |
282 |
119 |
BenQ XL2730Z |
120Hz |
309 |
191 |
Dell S2716DG |
120Hz |
328 |
118 |
Eizo FG2421 |
120Hz |
386 |
257 |
Eizo FS2735 |
144Hz |
331 |
180 |
LG 34UC79G |
144Hz |
267 |
141 |
LG 38UC99 |
75Hz |
308 |
213 |
Note:
Pulse Width setting at max where applicable.
*Note 2: The Acer XB270HU was later updated to include a 120Hz mode, which will produce a
slightly darker maximum luminance
Blur Reduction Tests

ULMB
enabled, central screen area
Of course the main thing we want to test is what
improvements the Blur Reduction mode offers when it comes to motion clarity and
gaming. We were pleased with the results we'd seen from LightBoost backlights
when we tested them, and also from the natively supported blur reduction
feature on other displays including the other popular TN Film gaming models
we've tested.
We were very pleased with the results
here as we had been on other blur reduction displays, with an obvious and marked improvement in perceived motion blur experienced.
Tracking of moving objects became much easier and the image looked sharper and
clearer. We used the BlurBusters full-screen
TestUFO online motion test (all ULMB supported refresh rates) as well to put the
feature through its paces and were pleased with the results. The upper half of
the screen was a little clearer than the bottom, and in the bottom third of the
screen some strobe cross-talk became apparent. It is impossible to eliminate
strobe cross-talk completely due to the way they operate, but the important
thing is whereabouts on the screen this manifests itself and to what level. The
central region (as pictured above) is probably the most important since that's where a lot of your
gaming focus will be, where crosshairs and the likes are. We were pleased that
there was minimal cross-talk here in the central region and the image looked
very good. Having the ability to alter the strobe length through the PW setting
was also very useful, and you could tweak it to your preference to reduce even
more
of the persistence if you wanted, as long as you didn't mind sacrificing some
brightness. With the high maximum brightness potential of the PG258Q when ULMB
was enabled, this was at least possible to do, as you have a decent brightness
range to play with.

ULMB
enabled, upper, middle and lower screen area cross-talk
Another very good implementation of a strobe backlight
system here, we were impressed. It's probably the best we've seen actually so
far, considering the high brightness potential. We suppose the only minor quibble is the
inability to operate the feature at 200 or 240Hz or in an ideal World, at the same time
as using G-sync. We suspect that most systems will struggle anyway to
consistently offer 200 and 240Hz refresh rates for a lot of games, so perhaps it
was a deliberate decision by Asus to limit the ULMB to 144Hz maximum. There's
obvious blur reducing benefits and you still get nice high frame rates anyway so
it's no massive deal.

Pursuit Camera Tests
We've already tested above the actual
pixel
response times and other aspects of the screen's gaming performance. We
wanted to carry out some pursuit camera tests as well to give an even more
complete idea of the performance of this screen.
Pursuit cameras are used to capture motion blur as
a user might experience it on a display. They are simply cameras which follow
the on-screen motion and are extremely accurate at measuring motion blur,
ghosting and overdrive artefacts of moving images. Since they simulate the eye
tracking motion of moving eyes, they can be useful in giving an idea of how a
moving image appears to the end user. It is the blurring caused by eye
tracking on continuously-displayed refreshes (sample-and-hold) that we are keen
to analyse with this new approach. This is not pixel persistence caused by
response times; but a different cause of display motion blur which cannot be
captured using static camera tests. Low response times do have a positive impact
on motion blur, and higher refresh rates also help reduce blurring to a degree.
It does not matter how low response times are, or how high refresh rates are,
you will still see motion blur from LCD displays under normal operation to some
extent and that is what this section is designed to measure. Further
technologies specifically designed to reduce perceived motion blur are required
to eliminate the blur seen on these type of sample-and-hold displays which we
will also look at.
We used the
Blurbusters.com Ghosting Motion Test which is designed to be used with
pursuit camera setups. The pursuit camera method is
explained at BlurBusters
as well as
covered in this research paper. We
carried out the tests at various refresh rates, with and without Blur Reduction enabled.
These UFO objects were moving horizontally at 960 pixels per second, at a frame
rate matching refresh rate of the monitor.
Overdrive Setting
= Normal

These tests capture the kind of blurring you would
see with the naked eye when tracking moving objects across the screen. As you
increase the refresh rate the perceived blurring is reduced, as refresh rate has
a direct impact on motion blur.
It is not
eliminated entirely due to the nature of the sample-and-hold LCD display and the
tracking of your eyes.
No matter how fast the refresh rate and pixel
response times are, you cannot eliminate the perceived motion blur without other
methods like blur reduction strobing backlights, which this model does also
feature.
As you can see, the perceived motion clarity
improves significantly as you increase the refresh rate from 60 to 144Hz levels
which is common for high refresh rate panels which operate up to this refresh
rate. The moving image becomes easier to track and appears sharper. As you can
see, there are then noticeable improvements in perceived motion blur as you
increase up to 200Hz and 240Hz refresh rate, as the frame rate increases
dramatically again. The moving image becomes clearer and easier to track and
it's a decent improvement over 144Hz. It was harder to see this difference when
we tested the AOC AGON AG251FZ since the overdrive control was not as
consistent, but here on the Asus we felt the difference was more noticeable. You
can tell from the pursuit camera tests above as well that there's an improvement
in motion clarity as you go from 144 > 200 > 240Hz. From a motion clarity point
of view, this makes it the fastest display we've tested to date. In practice it
might be harder to notice this in gaming, as you're starting to get into the
realms of diminishing returns as you get in to the 144Hz range we felt, and
perhaps it isn't needed for many users. But the pursuit camera tests and our
motion clarity tests showed some improvement that maybe a very keen eye will
spot in their gaming.


Note: optimal
overdrive settings used on each screen
We can also compare the pursuit camera tests at
60Hz and 144Hz compared with a couple of very fast and very popular gaming
screens above, including the recently tested AOC equivalent to this model, their
AGON AG251FZ with 240Hz. The performance is very comparable in actual perceived motion
blur between all three in practice, with very little to separate them. The
PG258Q has a slight edge at 144Hz as the image looks a little clearer and we
also know that there are lower levels of overshoot present. As we've shown a
little earlier, there are then the added benefits when increasing the refresh
rate to 200 and 240Hz.

If we compare the motion clarity at 240Hz between
the PG258Q and the AOC equivalent, you can see the better performance from the
Asus where the moving object was clearer and sharper.
ULMB
Enabled

This model also offers NVIDIA's Ultra Low Motion
Blur feature. When enabled, the moving image becomes even sharper and easier to
track with the eye across the screen. The strobed backlight helps reduce the
remnants of perceived motion blur nicely as we've discussed earlier. There is
some low strobe cross talk introduced which produces a slight ghost trial image
which is typical for a strobed backlight system.

Additional Gaming Features

GamePlus
hotkey - the screen features the ASUS-exclusive GamePlus hotkey for in-game
enhancements so you get more out of your game. The crosshair overlay gives you
four different crosshair options to suit the game you're playing. There's also
an onscreen timer you can position on the left of the display so you can keep
track of the elapsed gaming time; while the FPS (frames per second) counter lets
you know how smooth the game is running.
Asus
GameVisual Technology - basically a series of pre-set display modes to
optimize visuals for different types of content. There are 6 in total although
some are not specifically designed for gaming per se. This feature can be
accessed through the On Screen Display (OSD) settings menu. There are preset
modes for scenery, racing, cinema, RTS/RPG games, FPS games and an sRGB mode.
Aspect Ratio Control -
the screen does not offer any
aspect ratio control options through the OSD menu at all. This is due to a
limitation of using NVIDIA's G-sync technology. As we understand it, it is
locked to only one defined resolution, in this case 1920 x 1080 so it is not
possible (or easy) to provide G-sync support with a scaler. This isn't really a
problem for PC use since you can just control the aspect ratio through your
graphics card settings. Since most content is in the native 16:9 aspect ratio it
probably isn't an issue.

Lag
We have written an in depth article about
input lag and the various measurement techniques which are used to evaluate
this aspect of a display. It's important to first of all understand the
different methods available and also what this lag means to you as an end-user.
Input Lag vs. Display Lag vs. Signal
Processing
To avoid confusion with different terminology we
will refer to this section of our reviews as just "lag" from now on, as there
are a few different aspects to consider, and different interpretations of the
term "input lag". We will consider the following points here as much as
possible. The overall "display lag" is the first, that being the delay between
the image being shown on the TFT display and that being shown on a CRT. This is
what many people will know as input lag and originally was the measure made to
explain why the image is a little behind when using a CRT. The older stopwatch
based methods were the common way to measure this in the past, but through
advanced studies have been shown to be quite inaccurate. As a result, more
advanced tools like SMTT provide a method to measure that delay between a TFT
and CRT while removing the inaccuracies of older stopwatch methods.
In reality that lag / delay is caused by a
combination of two things - the signal processing delay caused by the TFT
electronics / scaler, and the response time of the pixels themselves. Most
"input lag" measurements over the years have always been based on the overall
display lag (signal processing + response time) and indeed the SMTT tool is
based on this visual difference between a CRT and TFT and so measures the
overall display lag. In practice the signal processing is the element which
gives the feel of lag to the user, and the response time of course can
impact blurring, and overall image quality in moving scenes. As people become
more aware of lag as a possible issue, we are of course keen to try and
understand the split between the two as much as possible to give a complete
picture.
The signal processing element within that is quite
hard to identify without extremely high end equipment and very complicated
methods. In fact the studies by Thomas Thiemann which really kicked this whole
thing off were based on equipment worth >100,1000 Euro, requiring extremely high
bandwidths and very complicated methods to trigger the correct behaviour and
accurately measure the signal processing on its own. Other techniques which are
being used since are not conducted by Thomas (he is a freelance writer) or based
on this equipment or technique, and may also be subject to other errors or
inaccuracies based on our conversations with him since. It's very hard as a
result to produce a technique which will measure just the signal processing on
its own unfortunately. Many measurement techniques are also not explained and so
it is important to try and get a picture from various sources if possible to
make an informed judgement about a display overall.
For our tests we will continue to use the SMTT
tool to measure the overall "display lag". From there we can use our
oscilloscope system to measure the response time across a wide range of grey to
grey (G2G) transitions as recorded in our
response time
tests. Since SMTT will not include the full response time within its
measurements, after speaking with Thomas further about the situation we will
subtract half of the average G2G response time from the total display lag. This should allow us to give a good estimation of
how much of the overall lag is attributable to the signal processing element on
its own.
Lag Classification
To help in this section we will also introduce a broader classification system
for these results to help categorise each screen as one of the following levels:
-
Class 1)
Less than 16ms / 1 frame of lag at 60Hz - should be fine for gamers, even at high levels
-
Class
2)
A lag of 16 -
32ms / One to two frames - moderate lag but should be fine for many gamers.
Caution advised for serious gaming and FPS
-
Class
3)
A lag of more
than 32ms / more than 2 frames - Some noticeable lag in daily usage, not
suitable for high end gaming

For the full reviews of the models compared here and the dates they were written
(and when screens were approximately released to the market), please see our
full
reviews index.
(Measurements in ms) |
|
Total Display Lag (SMTT
2) |
4.60 |
Pixel Response Time
Element |
1.70 |
Estimated Signal
Processing Lag |
2.90 |
Lag Classification |
1 |
|

Class
1 |
We have provided a comparison above against other
models we have tested to give an indication between screens. The screens
tested are split into two measurements which are
based on our overall display lag tests (using SMTT) and half the average G2G
response time, as measured by the oscilloscope. The response time is split from
the overall display lag and shown on the graph as the green bar. From there, the
signal processing (red bar) can be provided as a good estimation.
The screen showed a total average display lag of
only 4.60 ms as measured with SMTT 2. Taking into account half the average G2G
response time at 1.7ms, we can estimate that there is only ~2.90ms of signal
processing lag on this screen which is basically nothing. This is fairly typical
result from a G-sync screen and there are no issues here at all for gaming. The
result was the same at different refresh rates and with ULMB enabled also.

Movies and Video

The following summarises the screens performance
in video applications:
-
24.5"
screen size makes it a reasonable option for an all-in-one multimedia screen,
but being quite a lot smaller than most modern LCD TV's of course.
-
16:9
aspect ratio is more well suited to videos than a 16:10 format screen, leaving
smaller borders on DVD's and wide screen content at the top and bottom.
-
1920 x
1080 resolution can support full 1080 HD resolution content
-
Digital interfaces support HDCP for any encrypted and protected content
-
Decent enough range of connectivity options
for movie viewing and external device connection with DisplayPort and 1x HDMI
offered. Limited at the moment by the G-sync module.
-
Cables provided in the box
for both video
connections
-
Moderate AG coating provides reasonably clear images with no major graininess,
and without the unwanted reflections of a glossy solution. Some graininess
apparent as with other TN Film panels, but shouldn't present a problem in
movies.
-
Wide
brightness range adjustment possible from the display, including a maximum
luminance of ~488
cd/m2 but a rather limited lower
luminance of only 116 cd/m2. This should afford you good control for different
lighting conditions. Contrast ratio remains stable across that adjustment
range as well and is good for a TN Film panel. Brightness regulation is
controlled without the need for PWM and so is flicker free for all brightness
settings
-
Black
depth and contrast ratio are good for a TN Film panel at 859:1 after
calibration. Detail in darker scenes should not be lost as a result.
-
There
is a specific 'cinema' preset mode available for movies or video which is
cooler than our calibrated setup. Might be useful to tweak to your liking for
quick switching when you want to watch movies
-
Excellent
good pixel responsiveness which will handle fast moving scenes in movies
without issue. You will want to stick with the 'normal' overdrive mode to
avoid any overshoot issues present in the 'extreme' mode.
-
Viewing angles are limited due to the use of TN Film panel technology. May
cause issues with gamma and contrast shift if you change your line of sight or
have several people trying to see the screen at once. Not really an ideal
technology for movies as a result of this viewing angle limitation.
-
Good range of
ergonomic adjustments available from the stand, although quite stiff to use
most of them. It still should be easy enough to obtain a
comfortable position if you want to sit further away from the screen for movie
viewing.
-
No
particularly noticeable backlight leakage, and none from the edges which is
good. This type of leakage may prove an issue when watching movies where black
borders are present but it is not a problem here.
-
No
integrated stereo speakers on this model but there is a headphone connection if needed.
-
No
hardware aspect ratio options at all so connection of external devices may be
tricky if they operate at something other than the native 16:9 aspect ratio.
Shouldn't be an issue for modern Blu-ray and DVD players as well as games
consoles.
-
Picture in picture (PiP) and Picture By Picture (PbP) are not available.

Conclusion
The ROG Swift PG258Q was a
very impressive gaming screen and one of the best we've tested to date. The
response times were very low and the overdrive impulse was controlled nicely
across a wide refresh rate range, with only low levels of overshoot being
apparent. That's quite rare for a fast TN Film screen and we were impressed. The
high 144Hz range refresh rates made an obvious improvement to motion clarity
over 60Hz panels as we've become accustomed to with gaming displays for several
years now. But the improvements offered by 200 and 240Hz modes become apparent
on this display and offered again a decent improvement in motion clarity we
felt. The addition of a strobed ULMB backlight system was very welcome as well.
It was probably the best ULMB implementation we've seen so far in fact with a
very good maximum brightness potential. If only we could also use it at 200 and
240Hz! Lag was low as ever from a G-sync screen, and the G-sync function
provided the obvious benefits of that variable refresh rate technology.
There are a couple of
limitations with this screen though. Firstly it is TN Film based, and so you
have to live with the limited viewing angles and gamma/colour shift inherent to
the panel technology. While the screen offered a very good upper brightness
potential for ULMB use, this did come at the cost of a rather limited lower
adjustment range which might be problematic for those wanting to work in darker
ambient lighting conditions.
All in all though, as a gaming
display it was excellent and comes highly recommended if you're looking in the
fast 1080p TN Film space.
If you appreciate this review and enjoy reading and like our work, we would welcome a
donation
to the site to help us continue to make quality and detailed reviews for you.
Pros |
Cons |
Excellent pixel response
times, high refresh rate, great motion clarity and low lag for gaming |
Limitations of TN Film
technology when it comes to viewing angles particularly |
ULMB available and with high
brightness potential |
Minimum brightness adjustment
range is limited |
Nice ROG Swift design and
features |
G-sync module results in more
limited connectivity and scaler options |
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TFT Central Awards Explained
We have two award
classifications as part of our reviews. There's the top 'Recommended'
award, where a monitor is excellent and highly recommended by us. There is
also an 'Approved' award for a very good screen which may not be perfect,
but is still a very good display. These awards won't be given out every
time, but look out for the logo at the bottom of the conclusion. A list of
monitors which have won our awards is available
here. |
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