profiling iMac Retina displays running OS X 10.10
Hello: I've been trying to profile two new iMac Retinas using an i1Display Pro and software. Both have the desktop set to medium gray. Using the advanced mode, I set the display type to White LED, the white point to D65, the luminance to 100cd/m2. Following advice found on www.imagescience.com.au, I've set the contrast ratio to 250:1 rather than native as I'd like the two displays to match as closely as possible. I use the default profile settings except that I change the profile version from 4 to 2. I choose the largest patch set. I choose to adjust brightness and contrast rather than using the ADC option and am able to adjust to 99 or 100 cd/m2, although it's not always the same on both monitors. After running through the measurement process, on my latest attempt I get white point results of 6506, luminance of 99 cd/m2 and contrast ratio of 278:1 on one display and 6522, 100cd/m2 and 275:1 on the other. Is this about as close as I'll get? It seems pretty consistent to me, but visually one display looks to be a more neutral gray while the other seems "warmer" and appears to have a slight magenta cast. I've tried profiling with different white point settings, but the mismatch seems to occur regardless of the choice I make. More than one viewer has the same impression. Can I expect to get the screens to match? I don't have a sense whether the difference in the results I get is large enough to account for the visual differences one sees. When I make a sample print and view it under the lighting we use I get what I consider to be a good match between the screen and print - it actually looks pretty consistent on both screens. However, the computers are in a lab space used by students and the question does come up as to why the screens don't match. I'd appreciate whatever advice/information that anyone can offer. Bruce -- Bruce Bumbarger Library Conservator Magill Library - Haverford College 370 Lancaster Avenue Haverford, PA 19041 610-896-1165
Bruce, please give directions directly to the imagescience instructions you have in mind. Cheers David David B. Miller, Pharm. D. member Millers' Photography L.L.C. dba Spinnaker Photo Imaging Center Bellingham, WA www.spinnakerphotoimagingcenter.com 360 739 2826
On Feb 24, 2015, at 8:40 AM, Bruce Bumbarger <bbumbarg@haverford.edu> wrote:
Hello: I've been trying to profile two new iMac Retinas using an i1Display Pro and software. Both have the desktop set to medium gray.
Using the advanced mode, I set the display type to White LED, the white point to D65, the luminance to 100cd/m2. Following advice found on www.imagescience.com.au, I've set the contrast ratio to 250:1 rather than native as I'd like the two displays to match as closely as possible. I use the default profile settings except that I change the profile version from 4 to 2. I choose the largest patch set. I choose to adjust brightness and contrast rather than using the ADC option and am able to adjust to 99 or 100 cd/m2, although it's not always the same on both monitors. After running through the measurement process, on my latest attempt I get white point results of 6506, luminance of 99 cd/m2 and contrast ratio of 278:1 on one display and 6522, 100cd/m2 and 275:1 on the other.
Is this about as close as I'll get? It seems pretty consistent to me, but visually one display looks to be a more neutral gray while the other seems "warmer" and appears to have a slight magenta cast. I've tried profiling with different white point settings, but the mismatch seems to occur regardless of the choice I make. More than one viewer has the same impression. Can I expect to get the screens to match? I don't have a sense whether the difference in the results I get is large enough to account for the visual differences one sees.
When I make a sample print and view it under the lighting we use I get what I consider to be a good match between the screen and print - it actually looks pretty consistent on both screens. However, the computers are in a lab space used by students and the question does come up as to why the screens don't match. I'd appreciate whatever advice/information that anyone can offer.
Bruce
-- Bruce Bumbarger Library Conservator Magill Library - Haverford College 370 Lancaster Avenue Haverford, PA 19041 610-896-1165 _______________________________________________ Do not post admin requests to the list. They will be ignored. Colorsync-users mailing list (Colorsync-users@lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/colorsync-users/spinnakerphotoimagin...
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Hello David: Thanks for the suggestion. The instructions I've been following can be found at http://www.imagescience.com.au/kb/questions/188/Calibrating%20Monitors%20Usi... . Bruce Bruce Bumbarger Library Conservator Magill Library - Haverford College 370 Lancaster Avenue Haverford, PA 19041 610-896-1165 On Tue, Feb 24, 2015 at 1:37 PM, Spinnaker Photo Imaging Center < spinnakerphotoimagingcenter@dnmillerphoto.com> wrote:
Bruce, please give directions directly to the imagescience instructions you have in mind.
Cheers
David
David B. Miller, Pharm. D. member Millers' Photography L.L.C. dba Spinnaker Photo Imaging Center Bellingham, WA www.spinnakerphotoimagingcenter.com 360 739 2826
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Thanks….that did it. Cheers, David David B. Miller, Pharm. D. member Millers' Photography L.L.C. dba Spinnaker Photo Imaging Center Bellingham, WA www.spinnakerphotoimagingcenter.com 360 739 2826
On Feb 24, 2015, at 11:41 AM, Bruce Bumbarger <bbumbarg@haverford.edu> wrote:
Hello David: Thanks for the suggestion. The instructions I've been following can be found at http://www.imagescience.com.au/kb/questions/188/Calibrating%20Monitors%20Usi... <http://www.imagescience.com.au/kb/questions/188/Calibrating%20Monitors%20Using%20an%20i1Display%20Pro>.
Bruce
Bruce Bumbarger Library Conservator Magill Library - Haverford College 370 Lancaster Avenue Haverford, PA 19041 610-896-1165
On Tue, Feb 24, 2015 at 1:37 PM, Spinnaker Photo Imaging Center <spinnakerphotoimagingcenter@dnmillerphoto.com <mailto:spinnakerphotoimagingcenter@dnmillerphoto.com>> wrote: Bruce, please give directions directly to the imagescience instructions you have in mind.
Cheers
David
David B. Miller, Pharm. D. member Millers' Photography L.L.C. dba Spinnaker Photo Imaging Center Bellingham, WA www.spinnakerphotoimagingcenter.com <http://www.spinnakerphotoimagingcenter.com/> 360 739 2826 <tel:360%20739%202826>
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On Feb 24, 2015, at 9:40 AM, Bruce Bumbarger <bbumbarg@haverford.edu> wrote:
I've been trying to profile two new iMac Retinas using an i1Display Pro and software.
Which software? That's critical. The offering from X-rite isn't best in class but netiher are the two dispalys you're working with so yes, that might be as close as you get. You will probably have to futz around with different settings to get the two to match. IOW, don't expect that you'll use identical settings for white point, cd/m2 etc for both to produce a visual match. The basic concept is the same in trying to get a print and display to visually match. The correct settings are those that produce the match. A guide to how to fix this: http://www.luminous-landscape.com/tutorials/why_are_my_prints_too_dark.shtml
the luminance to 100cd/m2
That might be too low for the units to natively hit that value. Depending on the display, it's age etc, that's a really low value to hit and may be part of your problem. Try 150cd/m2. You can try moving lower from there (although I don't know why you'd want such a low value).
It seems pretty consistent to me, but visually one display looks to be a more neutral gray while the other seems "warmer" and appears to have a slight magenta cast.
The warm/cool axis should be addressed with White Point target calibraiton settings but magenta/green is the opposite color axis and I don't know how well that can be fixed depending on the software you are using. Some products have only control over the other color axis.
When I make a sample print and view it under the lighting we use I get what I consider to be a good match between the screen and print - it actually looks pretty consistent on both screens.
That's a good sign.
However, the computers are in a lab space used by students and the question does come up as to why the screens don't match.
Other than the location, the two sets of displays, calibration, ambient lighting and print viewing conditions are identical? Sure the students are not adjusting the OSD controls? Andrew Rodney http://www.digitaldog.net/
Hello Andrew: Thanks for the response. Regarding the software I'm using, it's the current version of X-Rite's i1Profiler (v. 1.5.6). Do you have suggestions for profiling software that might work better with the iMacs? Which software? That's critical. The offering from X-rite isn't best in
class but netiher are the two dispalys you're working with so yes, that might be as close as you get.
I was aiming for the 100 cd/m2 based on suggestions at http://www.imagescience.com.au/kb/questions/188/Calibrating%20Monitors%20Usi... and also because that seems to match the brightness we get using the viewing setup we have (Solux bulbs in clip-on lamps, not a viewing booth). Do you think it would be worthwhile to move the lights around to increase the light level? I may do that and also up the luminance target I'm aiming for.
the luminance to 100cd/m2
That might be too low for the units to natively hit that value. Depending on the display, it's age etc, that's a really low value to hit and may be part of your problem. Try 150cd/m2. You can try moving lower from there (although I don't know why you'd want such a low value).
The two machines in question sit side-by-side, so conditions are pretty close. I wondered about the possibility that someone has been messing about with the controls and have posted notes asking that everything be left as-is, but who knows whether the request is being heeded.
Other than the location, the two sets of displays, calibration, ambient lighting and print viewing conditions are identical? Sure the students are not adjusting the OSD controls?
Andrew Rodney http://www.digitaldog.net/
Thanks for the link to the Luminous Landscape article. I'll see what I can do based on some of the suggestions. Bruce -- Bruce Bumbarger Library Conservator Magill Library - Haverford College 370 Lancaster Avenue Haverford, PA 19041 610-896-1165
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
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 <lists@colorremedies.com> 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
On Feb 25, 2015, at 9:23 AM, Bruce Bumbarger <bbumbarg@haverford.edu> wrote:
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.
Not just LEDs. CTT is a range of colors. So YMMV. That's why you may see two different CCT values for each display while getting a visual match. Andrew Rodney http://www.digitaldog.net/
participants (4)
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Andrew Rodney
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Bruce Bumbarger
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Chris Murphy
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Spinnaker Photo Imaging Center