iMac resolution question
First impressions were not as good as I imagined, guess I have been looking at a Retina screen for that long the 27" screen did not appear "sharp" at all?
Is it just me? Or is this drop in resolution normal?
The 27" iMac's display has a resolution of 2560 x 1440 pixels, which is normal for a good 27" monitor. Like the iPad and the Retina MacBook Pros, it has a LED-backlit IPS LCD panel. However, it is not a Retina display.
Given the stated physical and pixel dimensions, the iMac's screen has a pixel density of just under 109 pixels per linear inch. The 13" and 15" MBPs have pixel densities of 227 and 220 pixels per inch, respectively. The fifth-generation iPod Touch and the iPhone 5 have a pixel density of 326 pixels per inch (slightly exceeding that of Apple's first laser printer!)
The iPad 3/4 come in at 264 pixels per square inch. So if you're viewing text that you have scaled up to a particular physical size (same on both the iMac and the iPad), the iPad can render that text with 5 to 6 times the number of (smaller) pixels, thus improving fine detail. (Another wrinkle: the iMac might deliberately be "blurring" the text with grey pixels, to simulate the proper outline within the means available, while the iPad might be drawing hard outlines, going on the assumption that by the time it reaches its resolution limit, the human eye can't spot any approximations.)
For the 27" iMac to match the iPad, it would need roughly 6200 x 3488 pixels, and a video card up to the job of driving the equivalent of 5 to 6 of today's 27" monitors. So no, it isn't fair to expect the iMac to match the iPad. Yet.
I would suggest comparing the 27" iMac screen to other good 27" IPS monitors.