Grayscale Tracking And Gamma Response
Our grayscale and gamma tests are described in detail here.
Dell's UP2715K has many calibration options and color presets so we thought it best to show you everything. There are quite a few charts ahead but it should help users decide the best way to optimize this monitor.
From the grayscale standpoint, the default Color Temp mode looks pretty good. The errors run slightly green as brightness increases but the monitor is perfectly usable this way. We don't recommend adjusting the color temp slider unless you want more blue or more red in the image.
Moving to the Adobe RGB and sRGB presets we see a visible shift to red. These are factory-calibrated modes but we think they have room for improvement. Dell claims errors under 2dE on the enclosed data sheet but our tests showed average levels around 4dE.
Next, we worked with the Custom mode, which has full control of every parameter. With no changes, it looks about the same as Color Temp, which means a slight green tint.
We only had to change the RGB gains to achieve this excellent result. This is what we'd expect of a premium professional product like this. There's nothing to complain about here.
The auto-cal software does a decent job but there is a little blue in the Adobe preset we created. It's barely visible in actual content and the improvements in gamut accuracy are well worth a little aberration in grayscale. You'll see those results on the next page.
The sRGB preset we created in the Cal 2 memory is visually perfect. All errors are below 2dE except 100 percent, which is still invisible at less than 3dE.
Here is our comparison group.
4.35dE represents the Color Temp mode. Custom, sRGB and Adobe RGB presets measure about the same. As a professional product we think the UP2715K should offer better results out of the box, especially considering that other Dell pro monitors we've tested measure better in their default states.
Using the auto-cal software returned decent results of 1.22dE for sRGB and 2.68dE for Adobe. The best possible grayscale tracking is found in the Custom mode where we achieved .95dE. That mode has a less-accurate color gamut though, and no option for sRGB. We still maintain that using auto-cal with the Cal 1 and 2 modes is the best course of action.
Each image mode yielded a different gamma result. Color Temp is quite good except for the 10-percent level, which is too dark. There is a little muddiness in the deepest shadows here but depth is otherwise good.
The Adobe RGB and sRGB presets have the worst gamma tracking of all. The curve runs too dark across the board with visible clipping of detail at 90 percent where there's a significant spike.
In the Custom mode you can specify a PC (2.2) or Mac (1.8) gamma and both measure well except for the 10-percent point. Calibration has no effect on the results, which look the same both before and after.
Near-perfect gamma performance is possible using the auto-cal software. There are no issues to report in either Adobe RGB or sRGB modes.
Here is our comparison group again.
The UP2715K's comparison results are based on the aforementioned programmed (Cal 1 & 2) Adobe and sRGB modes we created. The auto-cal software creates the best possible result and puts it among the best professional screens we've tested to date. A .09 variation in values is about as close to perfect as one can get.
We calculate gamma deviation by simply expressing the difference from 2.2 as a percentage.
An average value of 2.21 is visually identical to a perfect 2.2 result. There are no gamma issues whatsoever when using the provided calibration software.