Bump/dent in shadows of tone response and calibration curves

[Emil Ingelman Sahlen]

I calibrated my BenQ SW320 display in a MacBook Pro using a Colormunki Display. I calibrated to a pure power gamma 2.4 (relative, black output offset 100%) and used ~100 patches for profiling.

As shown in attachments, calibration curves have a dent and tone response curves have a corresponding bump in the shadows. Is this normal?

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[Vincent]

Plot resulting gamma (X input, Y gamma, from profile validation), you’ll see it easier than compared to L* (TRC graph). Calibration curves do not matter since its shape depends on how bad your display TRC was before calibration.
Also it seems that you did not use BPC (L* for 0 input seems non 0 in TRC) and you are using 3 TRC, since you are using macOS and its faulty color management engine you should stick to default simple idealized profiles, since it is the pnly type macOS understands for apps that use its color management engine.

[Emil Ingelman Sahlen]

I see, I’ll take a look at the effective gamma.

The reason I did not use default profiles is that I only really care about color in DaVinci Resolve and Lightroom and for Resolve I can disable ColorSync and just use a LUT and Lightroom will work with the more complex profiles, if I understand correctly.

Or have I misunderstood? My impression is that MacOS will incorrectly handle more complex profiles but will apply VCGT from the profile. Thus, if I use the profile together with a Resolve 3DLUT that doesn’t have VCGT applied, then it will work correctly, no?

[Vincent]

I forgot one iportant thing. It is pointless to calibrate to g2.4 on a color managed enviroment. Stay close to native gamma which is likely to be close to 2.2.
Photoshop & other apps will undo calibreted TRC because color management and for software LUT3D as long as display behavior matches detailed profile, you can embed in LUT3D any TRC transformation you want.

So:
-general purpose & system wide: set native gamut, D65, make a 2.2g simple profile (as macOS needs)
-reuse VCGT calibration and make a detailed XYZLUT profile. This will not be installed. You will use it in LUT3D creator standalone app (displaycal folder) to make as many LUT3D you want to whatever colospaces you need. For example and in a low contrast IPS display like yours, in LUT3D creator,  source colorspace rec709 gamma 2.4 relative, destination colorspace the custom XYZLUT profile, VCGT yes or no depening on which ICC will be as default display profile in OS (“no” if you wish to keep that custom matrix profile system wide)

There are other threads explaining this.

• This reply was modified 2 years, 3 months ago by Vincent.

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