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: Bruce Bumbarger <email@hidden>
- Date: Wed, 25 Feb 2015 11:23:36 -0500
Hello Chris:
Thanks for your response. As may be evident from my posts I'm a relative
novice with this, so some of the first couple of paragraphs goes a bit over
my head. Reading a Wikipedia article -
http://en.wikipedia.org/wiki/Color_temperature - I see that CCT as used
with LED light sources seems to represent an approximation - a way of
assigning a black-body color temperature that corresponds most closely to
the human color perception of the light emitted by the LED. I gather that
the difference I see between the displays is a result of the errors that
creep in during this process, the limited precision of the colorimeter, &c
and that I'm not likely to ever get a complete match.
I'll focus on tweaking the luminance value, aim for a satisfactory match
between the paper/print sample and screen image, and figure out a way to
keep students from using the keyboard controls to adjust the brightness.
Thanks again.
Bruce
--
Bruce Bumbarger
Library Conservator
Magill Library - Haverford College
370 Lancaster Avenue
Haverford, PA 19041
610-896-1165
On Tue, Feb 24, 2015 at 5:46 PM, Chris Murphy <email@hidden>
wrote:
> 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
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Colorsync-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden