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.
The HP E271i measures very well in its stock configuration.
If ever there were a monitor that doesn’t really need a calibration, the E271i is it. This is the best run we’ve ever seen from an uncalibrated screen. In fact, its stock average Delta E value of 1.64 is the lowest of all the monitors we’ve tested this year. Nitpickers like us will note the slight rise in red from 30 percent on up. Even though HP doesn’t advertise this panel as factory-calibrated (and it certainly isn’t at this price), it might as well be with numbers this good.
After a quick and easy calibration in the Custom RGB mode, we generated an even better chart.
While there are monitors with slightly (very slightly) better grayscale performance, it doesn’t really get much better than this. An average Delta E value of .84 puts the HP up with the best displays for grayscale accuracy.
You can see that neither a monitor’s resolution, nor its price tag affects its grayscale performance.
The HP sits quite comfortably at the top of the out-of-box grayscale chart. This is a value-priced screen marketed principally for business use. Yet, it could work in a graphics environment, so long as the wider Adobe RGB 1998 gamut is not required.
Let’s see how things stack up after calibration.
The HP runs close to the majority of the pack at just under one Delta E. We think it’s reasonable to expect any monitor today to come in under two Delta E after calibration, so when they average below one, that’s just icing on the cake. If you were to line up all the monitors in the group together, you would not see a difference in their grayscale accuracy with the naked eye.
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.
This was the only test where HP falls short. With all of its other numbers coming in at excellent levels, we were surprised to see such poor gamma. We tried adjusting the Black Stretch, as well as the Brightness and Contrast controls to help, but the above graph was the best we could achieve.
You can see the trace never gets to the 2.2 standard, and as the signal rises, the brightness level continues to get too high. The visible result is that mid-tones and bright highlights are slightly flat, as if there was a subtle haze in those parts of the image. Productivity apps look fine, since they operate mostly at the darkest and lightest extremes. But photos and graphics don’t quite have the extra depth that they should. HP does a superb job at the extremes of the brightness scale, as evidenced by the great contrast numbers. Unfortunately, the too-bright gamma counters some of the E271i's advantage.
Here are the gamma numbers put up against the same group of monitors.
With a span of .49 from the lowest to highest gamma value, HP doesn't end up on the bottom. However, it certainly has room for improvement. A gamma preset control would help raise the trace closer to 2.2, though it'd require a multi-point adjustment to flatten out the tendency of the gamma to drop as the signal becomes brighter.
We calculate gamma deviation by expressing the difference from 2.2 as a percentage.
The I2757FH we tested back in January is still the only display to measure a perfect 2.2 for average gamma. The E271i misses the mark significantly with a 12.7 percent deviation from the standard. Again, just the addition of a gamma preset would be a vast improvement in this metric.