Grayscale, Gamma & Color
Our 34WK650 came with a factory calibration data sheet, but it didn’t specify which mode it used. We came close to LG’s results in the default Custom mode before adjustment. After our tweaks, we measured reference-level accuracy.
Our grayscale and gamma tests are described in detail here.
The first chart represents the Custom mode as-delivered. All errors were under 3dE, which means the 34WK650 does not need calibration. For most users, images will look pretty good out of the box. The touch of extra blue shown in our measurement run served to brighten the picture slightly.
HDR Effect attempts to simulate HDR with SDR material. By pumping up the color temperature, it made the image appear brighter, if you could ignore the extra blue. But that extra blue is noticeable, especially in the all-important mid-tones. With many errors around 8dE, you’d have to accept a liberal interpretation of the white point. That mode also made a major change to gamma and color saturation, which we’ll illustrate below.
Afte we calibrated Custom mode, the 34WK650 proved itself capable of reference-level accuracy. Remember, this is a sub-$400 monitor. Few screens at this price point measure this good.
A 2.36dE average error means the 34WK650 does not need calibration. But when we used the HDR effect, the error climbed to 6.74dE and was clearly visible. Our adjustments to gamma and RGB sliders turned in a very small error score of .42dE, one of the lowest values we’ve ever recorded. It should be noted that the Gamma Mode 3 preset is required for this result; Gamma Mode 2 resulted in a slightly higher .91dE average error.
We saw some interesting results in the gamma tests. The dip at 90% visible in the first and third charts usually indicates a too-high contrast setting. But lowering that slider only made things worse. Ultimately, we raised it one click to make a slight improvement. We also chose Gamma Mode 3 to get more of the trace above 2.2. Gamma Mode 2, the default, looked a bit light in color to our eyes. If you want to experiment with the various gamma presets, know that you’ll have to re-adjust the RGB sliders each time because the white point changes visibly. In our case, after adjusting Mode 2, Mode 3 made things decidedly green, so we started over. Ultimately, the best picture came with the latter setting. HDR Effect, as you can see, alters gamma much like a dynamic contrast feature. It darkens shadow areas and brightens highlights to increase the perception of contrast. In the process, detail is obscured, giving the picture a flat and soft appearance.
The 34WK650’s curvy gamma trace averaged a perfect 2.2, but its values ranged by .5, which is higher than average. Highlights had a little extra punch, but fine detail was lost in some cases, depending on the content. While these results are unusual, they are by no means a deal-breaker.
Color Gamut & Luminance
For details on our color gamut testing and volume calculations, please click here.
Calibrated or not, the 34WK650’s color performance is hard to fault. The Custom mode delivered excellent accuracy in both saturation and luminance, with a low average error of 2.52dE. Most points were slightly over their targets, which is OK in a monitor with relatively low contrast. Luminance levels were nearly neutral with a slight rise at 100%, also not a problem.
HDR Effect pumped up saturation quite a bit in the mid-tones, which helped make up for the 34WK650’s lack of DCI-P3 color support. This ability will be a factor in our HDR test results on the next page. We feel SDR content looked best in the Custom mode with our recommended settings.
You can see where we fixed the magenta hue error mentioned earlier thanks to the effective Six Color feature. A white balance calibration wasn’t quite enough to bring that secondary in line. The end result was a slight gain in color accuracy to 1.98dE, barely visible but worth the small effort.
The small spread from first to last puts the 34WK650 on the same performance level as its rivals. There was no appreciable color difference between any of the monitors here. But if you’re looking for DCI-P3 coverage, the LG is right in the middle. It doesn’t bill itself as a DCI monitor, yet still managed to squeeze out just over 75% of that gamut. It hit 100% sRGB almost perfectly though, which makes it suitable for color-critical work in that realm. But for the most possible color gamut coverage, the Samsung takes the cake.
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