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I’ve been having some difficulty with calibration of an iMac screen (21 inch, circa late 2013).
In Seattle we have a cool non-profit organization called the Northwest Film Forum. They have a computer lab with about 8 iMacs, where struggling film makers can use machines with various software suites, for $5/hr (they also offer instruction courses).
I learned their screens were not calibrated, so I asked if they’d be interested in learning about the DisplayCAL process and borrowing my colorimeter to calibrate all the screens. They enthusiastically took me up on the offer.
I did a calibration on one of the machines, but it didn’t work. I left all the settings on auto/default, except I increased the patches to 425. After the calibration completed the screen was a bit lighter and the colors not as deep. When I re-checked the RGB balance I found that it went from the R and B being a step too low before, to a few steps too low after.
I ran and attached a Measurement report and Reports on Calibration Before and After, in case they contain important info.
That looks fine, but depending on the software you use for film work, you may have to setup that software for color correct output (e.g. create and use a 3D LUT – this can be done from the existing profile in DisplayCAL). What software are you using at the facility?
Hello Florian, they have Final Cut, the Adobe suite and probably several other film and photo programs.
However, I’m confused about the calibration I did. When I did the initial measurement the RGB was off a little bit. The iMac screen does not allow for manual adjustment of the RGB, just brightness, but I saw an earlier thread which said to skip that part and it will be fixed in the calibration.
After completing the calibration and installing the new display profile I did the measurement again, expecting the RG and B to be balanced, but the measurement showed it to be more out of balance than before the calibration, which led me to believe the calibration wasn’t working.
I saw an earlier thread which said to skip that part and it will be fixed in the calibration
Yes, but you need to set a whitepoint target if you want a specific chromaticiy or daylight/blackbody equivalent.
Hello Florian, I don’t know that I’m going to be able to grasp the technical complexity of this issue, but when I ran the calibration the color temp was 6,500, which came up as the default and I left it alone.
My assumption was that running the calibration process would improve the RGB balance, but each color measured further from the midpoint afterward. I expected there was an issue with the chosen settings, but nothing seems to stand out.
I don’t want to beat this thread into the ground, but I thought I’d respond one more time, in case I’m just misunderstanding the potential solution.
when I ran the calibration the color temp was 6,500, which came up as the default and I left it alone.
That should be fine (although if you were picky and aiming for the Rec 709 “D65” values, the color temperature target should be around 4 Kelvin higher, i.e. 6504 K, or a chromaticity of x 0.3127 y 0.329. For most intents and purposes, this difference is negligible though). Maybe I’m not understanding how you evaluate the result. What’s the exact procedure you’re using to do these evaluations?
I just went through the initial RGB balance, in the White Point Interactive Adjustment, to see where it was before moving on to calibration. The green was in the middle and red and blue were both a step low; since I can’t adjust this on the iMac, because it has no RGB adjustment like my Asus, I just ran the calibration, expecthing it would raise the Red and Blue.
However, I ran this measurement again after the calibration and the colors were even further from balance.
I just went through the initial RGB balance, in the White Point Interactive Adjustment, to see where it was before moving on to calibration. […]
However, I ran this measurement again after the calibration and the colors were even further from balance.
You can’t use this to evaluate calibrated grey balance because the calibration is inactive during interactive adjustment. Run a measurement report instead.
Hi Florian,
I am not trying to hijack the thread, but I have a similiar problem.
Or well, sort of.
I have then 5k iMac and resolutionwise I love the screen, but colors are a bit off. Now I also have a external NEC monitor where I can control RGB colors. Obviously that makes for a better correction, but after I have run DisplayCal the do not match at all.
Now contrast I get won’t be the same, but colors are very off. Is there some sort of setting I should put it in just for working with iMac screens. I am using the Spyde3 Pro module.
C
