Characteristics of the Fourth Generation iPad with Retina Display
There are not too many surprises with the fourth generation full size iPad (wouldn’t it be great if Apple gave these products functional names?). Its largely a refresh for the sake of updating the processor and moving the connector system to the new Lightning Connector. Both worthwhile improvements, but not anything to concern us here. Still, there are more questions to be considered with the new iPad mini.
Characteristics of the iPad mini
The screen of the iPad mini offers the pixel-count of the pre-Retina iPads, in a smaller form factor. Not retina resolution, but somewhere in between the non-Retina full size iPads, and the Retina versions, by way of its decreased screen size. Many will choose to live with this enhanced, but not “Retinaed” resolution (yes, I just turned Retina into a verb) in return for the convenience of the smaller form factor and the lower price of the new mini. But what about its color characteristics for serious uses? Has Apple taken a step backwards there as well, in order to make the new mini more cost competitive in its (already populated) size range?
The answer is yes, and no. As we know from previous testing, the Retina iPad screens (and the iPhone 5 Retina screen as well) have been updated from the earlier, twisted, sub-sRGB color space of early iOS devices, to a color space very close to sRGB. The gamut plot below shows the iPad 3, with sRGB overlaid, as that order provides the clearest indication of their match. The green primary of the iPad 3 actually exceeds sRGB by a bit, but overall this is a great match.
sRGB gamut over iPad3 gamut
We have also studied the gamut of earlier iOS devices, and seen how this gamut effects their display of web images (in sRGB) and web videos in Rec-709, which shares a number of key characteristics with sRGB. The image below is the second generation iPad, overlaid on the third generation iPad, showing the smaller and twisted gamut of the earlier screens. There is no doubt that the color accuracy of the sRGB-sized recent devices is superior to the older devices.
iPad2 gamut over iPad3 gamut
Color of the iPad mini
With that background information in mind, lets look at the gamut of the iPad mini in relation to sRGB. First, its important to note that the white point (global color tone) of the iPad mini is close to the target value of 6500K, and the gamma (ramp from black to white) is very close to the target value of Gamma 2.2. In the image below, you will recognize the earlier, sub-sRGB gamut, and twisted primaries, with the added twist of primary green, and well as primary blue, being offset sufficiently from the sRGB primaries to lie outside of sRGB, making color correction that much more difficult.
iPad mini gamut in blue, compared to sRGB in red
Yes, this gamut looks quite familiar, as you can see by comparing it to the previous illustrations. The iPad mini does indeed revert to the smaller, twisted shape of the earlier iOS gamut. Apple seldom takes a step backward in their relentless move forward, but here we have one example of it. So, if you were considering getting an iPad mini for use as a photo or video portfolio, please note that these color deficiencies will effect your results.
It is quite likely that in the next generation of iPad mini, Apple will move the device forward to a full sRGB gamut (and who knows, perhaps Retina resolution as well). So at this time the larger gen 3 and gen 4 iPads are the optimal iPads for display of critical color. It is possible to color calibrate the iPad mini with Datacolor’s SpyderGallery application, to produce corrected color (within the limits of the reduced gamut) in the Gallery viewer, or in other Apps if you launder your images through SpyderGallery. But for color critical uses, it may be worth holding off for a generation, to see what Apple has up its sleeve next time for the iPad mini.
Credits: C. David Tobie, Copyright 2012. Website: CDTobie.com Return to Blog’s Main Page