The ASUS VS239H-P's panel has a pixel pitch of 0.2655mm, typical of 1920x1080, 23-inch monitors. Compared to 24-inchers with a 1920x1200 resolution, while you do lose some screen real estate due to the reduced height, the good news is that it will fit your full HD content perfectly, without any black bars at the top and bottom. To get the sharpest image, we recommend using either the DVI-D or HDMI input, and (of course) running it at its native 1920x1080 resolution. DVI and VGA cables are bundled in the box, but not HDMI.
Unlike some other monitors, the VS239H-P doesn't have a Text or Internet video preset. For most types of content, we found the Standard preset to be adequate. Theater mode lowered the brightness a notch, and added a bit of punch to the colors, so we can imagine some users would prefer it for movie-watching. Skin tone presets can also be adjusted here (in fact, they are available in all but the Standard and sRGB modes). And since it's using an IPS panel, viewing angles are very good (ASUS claims 178° for both horizontal and vertical). On the flip side, the dynamic contrast mode (ASCR) didn't give us any significant visual quality boost; eventually, we turned it off.
The sRGB preset lowered the white luminance even further to 150cd/m2. Strangely, colors became 'cooler' due to a jump in color temperature to 7,400K.
The VS239H-P has a gray-to-gray response time of 5ms (14ms typical). The panel is likely to be an LG e-IPS panel that uses some form of overdrive technology to improve response times by altering the voltage to drive the liquid crystals. This improved responsiveness should translate to lesser 'ghosting' or pixel trailing, which is most evident in games or movies, where there's a lot of action fast-moving images.
Within the OSD menu resides a Trace Free setting that's used to improve the pixel latency. Six settings are available: 0, 20, 40, 60 (which is the default), 80, and 100; the higher the setting, the higher the level of response time compensation (RTC). Using the free PixPerAn software for testing response times, we took multiple shots for each Trace Free setting, and selected the best-looking one to show below.
Using a camera with a high shutter speed, the effect of Trace Free can be observed easily. (It certainly beats eyeballing each level.) The difference from 0 to 40 was minimal. Trace Free at 60 looked the best with very little motion blur, though you can see a very slight shadow behind the speech bubble. At 80, the dark halo behind the speech bubble and yellow head, and the pale halo trailing the moving car are indicative of an overshoot error. At 100, the error worsened; trailing behind the speech bubble, the yellow head, and the car were separate and very distinct dark and white halos.
Obviously, Trace Free at 100 is too aggressive. The default Trace Free level of 60 is indeed the best, as it produces the least amount of ghosting artifacts.