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I bought a Colormunki Smile a few months ago, in order to calibrate my monitor. When I used it with DisplayCal right after buying it, the profiles produced had gamuts covering 95% to 99% of the sRGB gamut. When I decided to recalibrate a few months later, though, the coverage was closer to 80%! I tried changing settings, using the laptop preset, and even calibrating on a clean Linux system, but now I can’t even get it to push 90%. I have a standard gamut laptop screen. Could it just be that I cannot find the right settings? If 50, what are they? Could my colorimeter have been damaged by heat or cold or X-ray radiation? How can I fix this?
The gamut coverage % should not be influenced by most of the settings except if you’ve set a calibration whitepoint target – on a laptop, the only way to adjust the whitepoint are the video card gamma tables, and as the chosen whitepoint moves away from native, this limits one or more of the color channels, thus reducing the gamut. Try calibrating to native gamut and see if you get the expected gamut coverage.
I just tried that. I used the default ‘Laptop’ preset, which has the color temperature as measured. I did increase the number of patches. and decrease the calibration speed. The gamut is still around 80%, but I still have those old 97% gamuts, so I know it cannot be that I misremembered.
The gamut is still around 80%
Seems odd. Unless something about the screen or the instrument has changed, you should get (roughly) the same gamut coverage every time. Feel free to attach the old and new profile, maybe some examination can explain what’s going on.
Btw, have you checked that you used the same colorimeter correction (if any) for each profile? That’s the only other thing I can think of that can have an influence.
The first file has 98% sRGB gamut coverage. The second is from much later and has 85% gamut coverage. Pretty much all of the later profiles are like this.
Should I need a colorimeter correction for a non-wide-gamut screen?
Technically this can help, but I see from the profiles that you used the “White LED” measurement mode of your ColorMunki Smile which should be fine.
The first file has 98% sRGB gamut coverage. The second is from much later and has 85% gamut coverage.
The profiles indeed look very different. If I wouldn’t know that this is the same display, I would think they were from two completely different devices. I’ll try explain the technical differences I found.
One observation that I made is that the display seemed to be much brighter when the newer profile was made than when the older one was created (259 cd/m2 new vs 105 cd/m2 old), but the weird thing is that the older profile seems to have recorded a higher black level which I would have expected the other way around.
The other observation is that despite a gamma 2.2 target being chosen during calibration, the newer profile has problems fitting the single shaper curve to the measured response, resulting in a higher recorded overall gamma that is closer to roughly 2.5, hinting that the simple shaper + matrix model is not able to achieve a good fit to the measurement data due to the latter’s non-linearity (this is also apparent in the older profile, although to a lesser extent, the high average profile self check of around 6 delta E is an indication). Creating a LUT profile does a much better job at representing the display device’s actual response.So, the first thing I’d try is to reduce the brightness level of the display to that of the previous profile, and then calibrate & profile to check if the result is more in line with the older profile. If it is, this would indicate the display is just behaving weirdly at high brightness. If not, this could also indicate a problem with the ColorMunki (although it does seem unlikely if it was stored properly, given that it is only few months old).
Could passing through an airport scanner have damaged it, by any chance?
I don’t think so. Only thing I can think of that could damage the instrument (the gelatine filters) in such a short amount of time is extreme heat or extreme humidity (or a combination thereof).
Well, here is a profile made with the ‘Laptop’ preset and XYZ LUT+Matrix, at a much lower brightness (around 120 cd/m^2). Still a pretty small gamut.
Either your instrument indeed took damage, or there has something changed about your display.
Well, I tested it on a desktop monitor, and it does not seem to be the instrument. The first profile is from a few months ago, and the second I just made. Clearly the gamuts are quite similar. It would seem, then, that the instrument is not at fault. I don’t really see how the gamut of a screen could drift, let alone over only a few months.
