LG 34UM95 34-Inch Ultra-Wide QHD Monitor Review

Results: Grayscale Tracking And Gamma Response

The majority of monitors, especially newer models, display excellent grayscale tracking (even at stock settings). It’s important that the color of white be consistently neutral at all light levels from darkest to brightest. Grayscale performance impacts color accuracy with regard to the secondary colors: cyan, magenta, and yellow. Since the 34UM95’s CMS can’t correct all color gamut errors, accurate grayscale is key.

LG's 34UM95 is set to its Custom picture mode by default. The resulting un-calibrated grayscale is just a tad cool. The error is barely visible and only at the 70- and 80-percent levels. Out-of-box performance is definitely above average.

If you don’t plan to calibrate, we recommend using the Photo mode instead.

As you've seen, the Photo mode offers a little more light output and its grayscale accuracy is about the same as Custom. You still have access to Brightness, but the Contrast and Color controls are locked out. The errors are visible at the 70- to 100-percent levels, showing just a hint of green. We still consider this above-average performance.

Here is our calibrated result:

Calibrating the Custom mode yields the best grayscale accuracy. You give up around 20 percent of the available contrast, so some users might opt to leave the RGB sliders and/or the Contrast control alone and simply adjust Brightness to taste. Either way, we expect you’ll be satisfied.

Here is our comparison group:

An average error of 2.37 Delta E is comfortably below the visibility point. Most brightness levels have no visible error at all. The ones that do will take sharp eyes to detect.

Calibration puts the 34UM95 on par with many professional displays.

It’s hard to find a monitor much more accurate than this. We think the compromise in contrast is worth such an excellent result. Since we were unable to try out the automatic calibration, we can’t say whether it's possible to get even better numbers. Visually, however, you wouldn’t be able to tell the difference.

Gamma Response

Gamma is the measurement of luminance levels at every step in the brightness range from 0 to 100 percent. It's important because poor gamma can either crush detail at various points or wash it out, making the entire picture appear flat and dull. Correct gamma produces a more three-dimensional image, with a greater sense of depth and realism. Meanwhile, incorrect gamma can negatively affect image quality, even in monitors with high contrast ratios.

In the gamma charts below, the yellow line represents 2.2, which is the most widely used standard for television, film, and computer graphics production. The closer the white measurement trace comes to 2.2, the better.

LG's 34UM95 has three gamma presets, but all of the charts we’re showing represent the Gamma 1 option. Our intent is to illustrate the difference between the Custom and Photo modes, along with the impact of Black Level.

You can’t change the gamma in Photo mode, so you’re stuck with tracking shown above. Luminance errors become brighter as you move towards 100-percent brightness. In actual content, the image lacks a little depth compared to one with a flatter gamma trace.

In Custom mode, you have a choice of High or Low for the Black Level control.

The differences are subtle. However, set to High, the trace stays below 2.2 throughout the entire brightness range. At 90 percent, the error maxes out at 4.1 cd/m2, which is barely visible.

We think image quality is superior at the Low setting.

I realize it's only a small change, but I can really tell the difference looking at actual content. The error starts a little too dark and slides under the line at the 40-percent mark. Now the maximum error is 3 cd/m2.

Here is our comparison group again:

The average of our tested monitors is about .27. LG's 34UM95 doesn't demonstrate the flattest tracking we’ve seen, but it’s pretty close to our standard.

We calculate gamma deviation by simply expressing the difference from 2.2 as a percentage.

The 34UM95’s deviation result is a good deal better than average. Gamma 1 with the Black Level set to Low definitely produces the best numbers in our gamma tests.

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