Please see the previous articles in this series:
The graph above compares the color gamut of earlier iPads to the new iPad. The difference is quite apparent. Ever since the days of the early color screen iPods, Apple’s iTunes app has been doing color conversion before creating down sampled images for sending to what are now called iOS devices. This could be tested by tagging the same image with a larger and a smaller color space, while not changing the actual image colors. If iTunes was ignoring incoming color profiles, the images would be identical on the iOS device. If images were being converted, then they would end up being different, as they would be converted from different source spaces. The latter was true, showing that images were converted on the way to the device. But converted to what? We jokingly called it iPodRGB, then later iPhoneRGB, and later still iPadRGB.
Now that Apple has created its first iOS device with a noticeably different color gamut, are they converting files differentially for the different device gamuts? Certainly they are creating different file sizes and resolution for different devices; the same file is larger, when rendered through iTunes to a new iPad, then it is when rendered to an earlier iPad. But more to our point: the color is different as well. E-mailing the same image “back to the Mac” from the new and an older iPad results in versions which are both different in size, and different in color. Resizing them to an approximate match, and overlaying them in an animated GIF results in the image below.
I apologize for the blinking image, but it is the most efficient way to show the changes. “What changes?” you may ask. And its true: the number flashes from 2 (older iPad) to 3 (new iPad) and the grid move a pixel or two, but the colors really don’t seem any different. In order to produce an animated image, its necessary to use the GIF format, which offers lower color bit depth than newer format. So for the most part, the minor differences in color are lost. But even in Photoshop at full color depth, the difference tended to be indistinguishable to the eye. However the RGB values of many patches were as much as several points different. So this may not be as big a deal as the headline “Images sent to New iPad are Color Converted Differently” could make it seem.
In a practical sense, how does this matter to the end user who cares about color? The same way it did in the past: Apple’s secret iTunes conversion to unknown colorspaces for iOS devices was apparent to those serious about color long ago, and has not really changed. Sending the same image to any iOS device through iTunes does not end up with the same result as emailing the image, or otherwise transporting it to the iPad outside of the iTunes process. Images imported outside of iTunes are not downsampled to what Apple considers an optimal level, so your iPad may get full much faster. And then there is Apple’s unmentioned color conversion. But now, there are multiple, slightly different, iTunes color conversions; the plot, as they say, thickens.
Apple is attempting to make this all invisible and automatic, to simplify the end user experience. Those with more advanced needs are left to deal with these simplifications as best they can. The first conclusion you can draw is that importing images through iTunes to your iOS devices, then sending them on for other uses is not a good idea. Images you wish to have retain known colors should be emailed or otherwise sent to the device instead. On the other hand images in color spaces other than sRGB, such as AdobeRGB, will be more appropriate if converted though iTunes, though the best solution is to convert such images to sRGB before outputting them to any mobile or web usage. A further conclusion is that those concerned about color should use the consistent method of their choice for importing files to their iOS device, and avoid mixing and matching files from iTunes and other sources. And the final observation would be that using SpyderGallery for color managed display is still the best choice for controlled iOS color.