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The New Apple iMac and the DCI P3 colour gamut

As a long time Apple user I am used to them making decisions that could charitably be called ahead of the curve. For example, their early omission of floppy or CD/DVD drives in their computers, their experimentation with different form factors and materials like the original iMacs and the Apple Cube, or the radical design choices that led to the latest Mac Pro.

Some of their daring moves have worked and paved the way for the rest of the industry to follow and others have fallen by the wayside. In terms of colour management they were instrumental in forming the International Color Consortium and changing the way colour was handled across the computer industry. However, since putting ColorSync in every Mac OS they haven’t really done anything that radical in terms of colour, until now.

The latest Retina iMacs have a display that exceeds the colour gamut of sRGB. Over recent years all of the Apple products from MacBooks to iPhones have evolved towards having sRGB gamut displays, and this pretty much makes sense for the core consumer market Apple has. So, it came as quite a shock to find out that they had adopted a wider gamut display for the latest iMac, but the really odd thing is the gamut they have chosen.

Most wide gamut monitors aim to cover as much of the Adobe RGB (1998) colour space as they can and typically manage over 95%. Adobe RGB is a colour space developed by Adobe for the pre-press and printing market and since widely adopted by photographers. If Apple were going to go wide gamut then Adobe RGB would be the logical choice. But being Apple they thought differently. The colour gamut of the new iMac screen is the DCI P3 colour gamut developed for the movie industry.

DCI P3 Colour Gamut

Digital Cinema Initiatives is an organisation formed by all the big Hollywood studios to establish standards for digital cinema systems. One of these standards is the P3 colour gamut for digital cinema projection systems. As you can see in the graph below DCI P3 is larger than sRGB and similar in size to Adobe RGB but it does have significant differences. P3 is designed for projectors. If you are doing colour grading, special effects or editing for a movie then it makes sense for your monitor to support a similar gamut but all the customers I have that are in the movie business use high end Adobe RGB screens (like the EIZO ColorEdge range) that include DCI P3 emulation but also, crucially, are very accurate screens with their own colour calibration system. The P3 standard refers to more than just a colour gamut and also specifies a gamma curve and luminance level. So anyone actually needing to work in P3 needs a better screen than even the new iMac has. P3 is not a standard designed for consumers, and it has problems for any photographer, designer or prepress user when compared to the much more widely supported Adobe RGB gamut.

Green = sRGB, Red = P3, Blue = Adobe RGB

Why the DCI P3 Gamut is not a good idea

The main issue I have with P3 as a monitor colour gamut is that it is smaller than Adobe RGB in the cyan and green area so it covers less of typical CMYK printer colour spaces. It is larger than Adobe RGB in reds and yellows but even with larger gamut inkjet printers you loose more greens than you gain reds. So for the core markets for wide gamut displays – photographers and prepress – P3 is less suitable, but I suppose it is still an improvement on sRGB.

You’d think that being a cinema standard P3 would be better for movies but most online movie content has been mastered to the REC709 HD TV standard, that uses the sRGB gamut so you won’t actually see any benefit when viewing films.

In fact if you are viewing the content through a poorly colour managed browser the image will look oversaturated because the sRGB data won’t be converted to P3. And this leads on to the other downside of Apple switching to P3 from sRGB. Most web browsers and many none colour critical applications assume the monitor gamut is sRGB and do not convert colours using the monitor profile. Apple have supplied a P3 gamut profile for the new iMac that is set as default but even large parts of the Apple user interface aren’t colour managed so you can end up with very vivid dock icons and other elements if you use a wide gamut screen.

Apple have addressed the issue with the latest version of their web browser Safari. Safari 9 now converts all images or content tagged with a profile to the monitor colour space but also crucially assumes anything that is untagged is sRGB and so converts it so it looks correct on wider gamut screens.

Hopefully Safari’s update marks the wider application of proper colour management in the Mac OS and will lead to lots of little issues that people like me who have had wide gamut displays for years have had to put up with. In fact the issue of wide gamut displays over saturating none colour managed data has long been recognised by monitor manufactures who have built in sRGB emulation modes into wide gamut displays. Apple haven’t done this and so will have to fix it in their software. Developers of other applications may or may not address the issue.

Just because I can’t see the logic behind Apple’s gamut choice doesn’t mean there isn’t one from their point of view. Perhaps LG offered them a good price on the panels? Perhaps it marks the start of a wider switch away from sRGB? Could we see P3 iPhones soon? I don’t know. I do know that using P3 for the new iMacs muddies the water. When talking to customers about which monitor to use for colour critical applications I always warned them off iMacs, even the 4/5K ones, because they are overly bright, highly reflective, have no quality standards for uniformity or consistency, and had a small colour gamut. Now customers are going to come back to me and say that they are now wide gamut and I will have to further explain that it’s not quite the right wide gamut that you need.

UPDATE

If you want to know more about Apple’s adoption of the DCI colour space then read my article about the iPhone 7 & Colour Management.

Rob :

View Comments

  • Hi Rob,

    Just discovered your blog. Pity I hadn't sooner!
    I've just placed an order for a 5k imac having read a few reviews, seduced by the extra power on offer over my current set up and of course those 14 million pixels.

    My current set up is a 3 year old macbook connected to an asus pa279Q display calibrated with my xrite i1 pro. I like the asus but have never been convinced that the uniformity or viewing angles live up to the promise of the spec.

    So although it appears P3 may not be quite there yet in terms of photographers, if it can deliver 90%+ of adobe rgb and has low delta error readings will it really be a step down when compared to my curent set up? Is there anything I can do when profiling to it with the i1 pro to maximise the results it can achieve?

    Thanks
    Cormac

    • Looking at the spec and the reviews the Asus isn't a top flight display either, and you may get lucky with the iMac and get one that is uniform. You can always use the Asus with the iMac as well.

      Assuming you are using the i1 Profiler software with the i1 Pro use the advanced mode and the default calibration targets. When you adjust the iMac brightness to hit the target hold Alt and Shift while pressing the brightness button to get finer control. Then after calibration use the Quality checking and uniformity checking to test the screen and the calibration.

    • Interesting. A crude way to do it but I guess if the content is not not colour managed by the application it would be better than nothing. Any colour managed app would be convert correctly from the content profile to the monitor profile.

    • I'm afraid I don't know much about Flash. What I suggest is a quick test of the same footage on a DCI or other wide gamut screen and on a sRGB gamut screen. If the footage on the wide gamut screen looks more saturated then it's not being corrected.

  • So is there anyway to "activate" or calibrate for adobe rgb profile and not use the preinstalled P3 profile? This seems to be a major drawback for photography work if you can't get the adobe profile back through calibration. I have an xrite calibrator myself.

    • Hi John

      A monitor profile is always a measurement of the screen as it is. You can't pretend it has a different gamut. However, any colour managed application will convert from the image profile (in your case Adobe RGB) to the monitor profile so that you see the best rendition your monitor can achieve for any other gamut. Of course the alternative method would be to get a monitor with a gamut closer to Adobe RGB.

  • How do the 2017 iMacs compare?

    I currently use a NEC PA272W with the NEC calibrator attached to a MacbookPro. But performance wise I desperately need a faster computer with more memory. I love the NEC and I've never considered an iMac because I didn't want to give it up but now the performance and memory increase are too much not to consider.

    I'm a photographer so color accuracy is important. I guess I could keep both monitors since I'm used to using the Macbook Pro as a second monitor, but a 27" iMac is way more desk space.

    Thanks!

    • As far as I know more recent iMacs will still be using the DCI colour space. I would recommend using the NEC for anything colour critical. It's a good screen.