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Reader Question: Display Calibration vis a vis Apple iMac 5K

Get NEC PA302W-BK-SV at B&H Photo.

The quick summary: I prefer viewing images on the iMac 5K, but for evaluation and color correction and post processing, I use my workhorse NEC PA302W.

Note: if purchasing an iMac 5K, I recommend buying the 8GB iMac 5K configuration and then adding 64GB memory—this saves about $820.

David M writes:

I am very keen to purchase the new 2017 iMac 5K (not the Pro version) especially on the purpose to replace my old NEC 24" display which I purchased base on your recommendation sometimes ago.

But after reading one of your latest post on MPG an alarm turn on my head and after a bit research I have learnt that several brands claim their displays support over one billion colors albeit the the color tech behind the display is a sort of 8-bit plus 10 dithering (AFRC) and not 10-bit TRUE color as of NEC and Eizo for instance.

Hence my question, and probably of many readers of the blogs, is whether a photographer can make do with the 8-bit plus the 10-bit dithering of brands like LG, ViewSonic and recently Apple, or shall s/he inspires for the 10-bit true color versions ? Many thank in advance for answering the question whether return mail or as a subject of one of your blogs.

NEC PA302W wide gamut display

DIGLLOYD: I hadn't heard of this dithering, but I don't pay attention to consumer solutions. I think when Apple says 'billions of colors' it is probably real 10 bit especially when claiming "smoother gradations" and similar. The 10 bits (or 8 bits) refer to the values per color channel (R/G/B) for the fineness of gradation: 256 values per color for 8 bit, 1024 values per color for 10 bit, so 8^3 combinations for 8 bit (24 bit) color and 1024^3 combinations for 10-bit (30 bit) color.

Photographers have "made do" with 8 bit until very recently (24 bits for RGB, 16.7 millon color). an that includes the NEC PA series professional displays, and Eizo; this was due to the lack (until recently) of driver support for 10 bit (30 bit) color.

While I now use 10 bit support (30 bits for RGB, a billion color combinations) on my NEC PA302W and NEC PA322UHD, I'vd have a hard time saying it matters versus 8 bit. The changeover happened in late 2015, perhaps driven by the late 2015 iMac 5K. However, I did not notice any difference in my daily work. Still, 10-bit delivers an ultra-smooth tonal range free of stepping, which one can see just by doing a grayscale ramp, so it does matter for any such gradient, such as a sunset sky of varying hue and density.

What really matters in a display, particularly over time and for calibrating to a desired target, is the internal 14-bit true calibration available on a professional display that can keep the consistency year over year. And for some users, different calibration targets for different output media.

The real issue for professional color management is that there is no way to calibrate the iMac 5K display. So-called calibration which rounds 8-bit video card values is what I call faux calibration. When I asked an XRite representative whether 10 bit values were used for calibration, I the answer as I understood it is “no, no API”.

It is not possible to “calibrate” in quarter tones and mid tones when there is no precision to do so (e.g., 4 or 5 but no 4.7). With the internal calibration of the NEC PA series in 14 bit precision, the display itself is brought within one delta-E of the target, which is a vastly different than rounding-off integral values in the video card*. This is why I GAVE UP on faux calibration years ago and why I use the NEC PA302W to evaluate and prepare my images.

While I am very happy with the Apple profile for the iMac 5K for viewing enjoyment purposes, it could stray over time and as far as I know, it is generic to millions of iMac 5K machines (not custom for each). Moreover the iMac 5K display (late 2015 or mid 2017) is truly exceptional in its contrast range (deep blacks to very bright whites) and thus gorgeous for viewing and thus dramatically different in look and feel than what I see on my NEC PA302W. Perceptually this makes it very difficult for print matching—no print can match the contrast range or color saturation of the transmissive medium that is the iMac 5K display. One of these days I’ll just say the hell with prints though—a 32" 8K display will be too gorgeous too care much about print display.

* One reader recently wrote to complain of banding (stepping) after calibrating his iMac 5K with a popular vendor’s solution. I advised him to abandon it and use the built-in profile—the banding/stepping disappeared.

See also:

NEC PA302W wide gamut display

 

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