Re: profiling iMac Retina displays running OS X 10.10
Re: profiling iMac Retina displays running OS X 10.10
- Subject: Re: profiling iMac Retina displays running OS X 10.10
- From: Chris Murphy <email@hidden>
- Date: Tue, 24 Feb 2015 15:46:03 -0700
These temperatures, 6506K and 6522K, if they are on the black body
locus, should have these (D50 Lab) values:
100 .77 -21.73
100 .78 -21.57
CIE 1976 ∆E = 0.16
CIE 1994 and 2000 ∆E = ~0.08
Those differences are small. These are probably CCT values however,
which actually have a range noted by isotherms that can have
noticeable differences, i.e. two light sources with CCT 6000K can
appear different. You might care about the ∆uv rather than either ∆CCT
or ∆Duv, and for that you need CIE:XYZ/LAB/LUV or even xy and for Y
use the luminance values, for each display.
But for any of those computations to be worth while, and yet still not
tell you anything you haven't already figured out (they look different
but the similar is acceptable), you'd need to assume the colorimeter
sees the displays the same way a human observer does. And that's
almost certainly false. Even if the colorimeter has a calibration
matrix for itself and these specific make/model/batch of displays,
which likely isn't the case (I'm only aware of one project that
attempted to "crowdsource" this, do a lookup and apply something of a
custom calibration matrix on the fly, it was too high maintenance and
the metrology was unreliable), you're probably within the
reproducibility limits of the: measuring device + uniformity of the
displays + subtle differences in environment or surround between the
two displays + the course granularity of control available for
adjusting the white point.
So yeah, it's probably pretty decently close. I'm kinda surprised
you're able to get two iMac displays within one nit of each other
actually.
I agree with Andrew that the difference is probably made more
noticeable by having a relatively low white luminance. Your goal is
probably to get the display color temperature and white point to
approximate your reference media, be that some form of print media, or
a standard under a particular light source. That means some amount of
iteration to make that happen and you're probably best off doing that
visually anyway, and whatever the measured values end up being, those
are your aimpoints to replicate for subsequent calibration. This,
rather than a somewhat arbitrary aimpoint for possibly some other
workflow.
--
Chris Murphy
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