Well, I have a new iMac 20.5″ for a couple of weeks. It’s an amazing machine – fast, silent and extremely compact.
When I decided to go for an iMac, I was very suspicious about it’s display capabilities. When I powered-up the machine for the first time, I was surprised with the good display. (Good, but not even close to my NEC 2690Uxi2. The NEC 2690 is a wide gammut display, capable of displaying the whole large AdobeRGB space and a little bit over it.)
So what about the iMac display?
Well, at its factory setting, the display of the iMac has very dark blacks an because of this it can’t be used for any serious work without recalibration. How do I judge this? I have a self-made calibration chart, that I often use for quick evaluation about the qualities of display of my friends and clients. The chart has 5 levels of the darkest and the lightest grey tones, that should be visible on a calibrated monitor. If you do not see all 5 dark and light circles and squares, you monitor needs a calibration for sure. (Click the picture for full size!) Depending on your display manufacturer, model, technology etc., you display could or could not be calibrated successfully.

Please, do not use this chart outside Photoshop – this can be misleading, as it is very possible that other software you use may not have proper color management, especially on a Windows system. For example, even the latest version of Internet Explorer has no color management.
I have an i1 Dispaly2 calibration device, so I calibrated my iMac as soon as it was possible And what a nice surprise: the display turned very balanced, with good color and almost perfect rendition of the dark and light tones. Very useful for my everyday graphics and photo editing work.
On Mac, you have the ColorSync utility, that can display graphic chart of a color profile. So I decided to compare the profile I’ve made with the i1 calibrator and the factory profile against the sRGB profile, which is the minimum required from a display for graphic and photography editing work. And here they are:
The sRGB profile:
The default (factory calibration) profile of the 20.5″ iMac (2010)
The profile, made with the i1 Display2 calibration device
It’s not very hard to see that both display profiles are larger than sRGB.
To make it easier to see the difference between the three profiles, I placed both display profiles over the sRGB profile. The largest is always the display profile.
The factory profile compared against sRGB:
The profile, made with the i1 calibration device against sRGB:
My conclusion:
The display of the iMac 20.5″ 2010 is completely usable even for demanding users, especially for those that don’t use AdobeRGB or any other color space larger than sRGB. The display is capable of displaying larger color space than sRGB, but after calibration, a very small clipping of the green tones occur. The factory display profiles clips a very tiny part of the Red tones from the sRGB color space.
The factory display profile is not good. It darkens the blacks and if you work with this display profile, you will obtain in fact lighter tones than those you see on the monitor. Calibrate your iMac as soon as possible to be sure you get most of it’s IPS display panel technology.
If sRGB is not enough for you, just buy a good wide-gammut monitor and connect it to your iMac trough the mini-display port – you will have a nice dual-monitor system, a pleasure to work on.