Grayscale, Gamma & Color
Our grayscale and gamma tests are described in detail here.
We had to do a bit of experimenting to find the best possible starting point for calibration. Racing mode defaults to the User color temp. Without adjustment, the chart shows an obvious bias toward green. sRGB provides an identical result. Cinema has a better default gamma, but it selects the cool color temp preset. That is obviously too blue.
Returning to Racing mode, adjusting the RGB sliders, and selecting the 1.8 gamma preset is the way to an almost-perfect grayscale result. Errors are far below the visible point and tracking is exactly where it should be.
A premium display like the PG248Q should be a little more accurate out of the box. 5.97dE is a little too far past the visible threshold for a monitor that costs over $400. Luckily relief is only a few OSD changes away. If you don’t have the means to calibrate your monitor, please dial in our recommended settings. They’ll give you the stellar and accurate image quality this monitor is capable of.
The initial gamma measurement indicates a contrast control that is set too high. It clips highlight information and makes darker content look too bright. This has a deleterious effect on perceived contrast. TN and IPS don’t have the greatest black levels in general, but getting gamma right can go a long way towards creating the deep blacks and rich shadow detail we all crave.
Changing the preset to Cinema fixes the shadow detail issue, but now the mid and bright tones are too dark and murky. Calibrating only the RGB sliders fixes the grayscale nicely but the trace is still much too dark, running at around a 2.7 average.
Thankfully Asus has included gamma presets. Selecting 1.8 will bring tracking down near 2.2 where it belongs. It’s a pretty major shift in accuracy and one that has a significant effect on color saturation and luminance, which we’ll show you below. There is excellent performance baked into the PG248Q. You just have to know how to unlock it.
Our fixes have taken gamma tracking to an almost perfect level. The variation in values is miniscule. As far as its deviation from the 2.2 standard, it still runs a tiny bit dark, but we’re well beyond a visible issue now. And the PG248Q’s gamma performance is now equal to or above that of its competitors.
Color Gamut & Luminance
For details on our color gamut testing and volume calculations, please click here.
The gamma and contrast control settings we’ve been talking about have a visible effect on color quality. You can see why it’s important to measure color saturation at levels other than 100%. The outer points of the gamut triangle don’t change when we make adjustments but the inner ones (20-80%) do significantly.
Out of the box, the Racing mode isn’t too bad overall. Whites are shifted toward green as we mentioned earlier, but the primary and secondary colors aren’t too far off their hue targets. Red, green, and blue miss many of their saturation targets though, and that’s where proper gamma and contrast settings become important.
The Cinema picture mode only makes things worse by pulling more colors off target. Changing the color temp preset will help this mode somewhat, but Racing mode with a proper calibration is still your best bet.
As above, we’re showing the difference between the 1.8 and 2.2 gamma presets. Even though white balance has been dialed-in, the 2.2 option causes major shifts in saturation. This is something you’ll see in most content as a general lack of detail and depth. The picture looks muddy and flat. Simply changing the gamma to 1.8 has a miraculous effect. Now color looks natural at all brightness levels, depth and detail have returned, and you have an image that rivals many of the best displays we’ve reviewed.
Our initial color measurements indicated an average error of 4.55dE in Racing mode and 7.91 in Cinema. With our adjustments, which you can replicate, it drops to a scant 1.77dE. It’s enough to give the PG248Q a third-place finish in our comparison. We’re glad to see such good performance available in this monitor.
Gamut volume doesn’t have much impact on gaming, but our review subject almost fills 100% of the sRGB space. Consulting the CIE chart reveals a tiny under-saturation in red. It’s nothing you can see with the naked eye. Testing shows this screen to be at or near the top of all the gaming monitors we’ve tested for color accuracy.