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Asus PQ321Q 4K Monitor Review: Top-Shelf Ultra HD For $3500

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 computer monitors typically have no color or tint adjustment, accurate grayscale is key.

This is the PQ321Q’s Standard color mode with the grayscale preset at 6500K. The graph shows a slightly warm result, where red rises slightly with brightness. If you look at the Delta E errors, however, they are all under three, which means they’re invisible. We were perfectly happy to use Asus' display in an uncalibrated state.

Since our goal is always perfection, we used all of the available controls to try improving the grayscale result.

This is a near-perfect chart. The Delta E errors at 30, 70, and 80 percent are only .07! And every other level is well below one, except zero percent. We’ve never seen any display, of any type, turn in such strong results. We attribute the performance to Asus' high and low RGB sliders and the extremely precise resolution they enable.

Here’s our comparison group of the last six desktop monitors reviewed at Tom’s Hardware.

We said in our review of the Dell P2714T that it was a display that didn’t need calibration. Now we’re adding the Asus PQ321Q to the same list. An average Delta E error of 1.48 is pretty much negligible. You won’t be able to see it with a naked eye. Only our i1Pro knows the difference.

The calibrated result is even more impressive.

Considering the error at zero percent is 2.16 Delta E, the average figure of .53 is almost unbelievable. If you take that brightness level out of the equation, the average drops to an incredible .37!

Gamma Response

Gamma is the measurement of luminance levels at every step in the brightness range from 0 to 100 percent. This is 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 accepted standard for television, film, and computer graphics production. The closer the white measurement trace comes to 2.2, the better.

The PQ321Q’s gamma tracking is almost perfect except for 10 and 90 percent, which are just a bit too bright. The error at 10 percent represents only .72 cd/m2 and the 90 percent error is 1.85 cd/m2. That's too tiny to see without the aid of instruments.

Here’s our test group again for the gamma comparisons.

A variance of .21 indicates very tight gamma tracking. You can see from the graph above that the PQ321Q’s gamma is extremely accurate. You’ll need to change the gamma preset from Standard to 2.2 to accomplish this. This really helps improve image quality, even though the measured contrast is on the low side.

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

The PQ321Q is only 1.81 percent off the target value of 2.2, matching the very best displays we’ve tested. Along with grayscale, this is an area where we’re seeing consistent improvement in newer screens.

Christian Eberle
Christian Eberle is a Contributing Editor for Tom's Hardware US. He's a veteran reviewer of A/V equipment, specializing in monitors.