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I’m trying to calibrate my monitor using 2.4 gamma rather than 2.2 gamma, both to install as a profile, and to create 3D LUTs for ReShade and Resolve GUI. My monitor has a 2.4 gamma setting (confirmed as 2.36 with “Report on Uncalibrated Device”). I followed the wiki guides for creating 3D LUTs for the Resolve GUI – starting with the Resolve preset, setting the Tone Curve option under Calibration to Rec. 1886 2.4 Absolute, and disabling “Apply calibration (vcgt)” on the 3D LUT menu.
I did Calibrate & Profile, created a 3D LUT, and installed the profile. It looked like my gamma changed, and this was verified by “Report on calibrated display device” reporting 2.21 gamma.
How can I keep the 2.4 gamma, both on the installed profile, and in the 3D LUT? Also, looking back at my measurement reports for my reference monitor supplied by my Decklink, it looks like it is also at 2.2 gamma (using the Resolve preset).
Hi,
it is important to note that BT. 1886 (= 2.4 absolute gamma, black output offset 0%) is not the same as a 2.4 power curve – it takes into account the black level (and white level) of the display, thus in practice the overall gamma may end up closer to 2.2 than 2.4, as you have observed. BT. 1886 will only match a 2.4 power curve if the display black level is zero (e.g. OLED).
The tone curve parameters are highly configurable though: Setting the gamma from “absolute” to “relative” will make the curve match the desired gamma at 50% input, and setting the black output offset to a non-zero value will make the curve shape more resemble a power curve near black (at the expense of less even gradation out of black).
If you’d like to play with the tone curve parameters and create additional 3D LUTs from your existing profile, disable “Create 3D LUT after profiling” on the “3D LUT” tab.
Is this something I can also change for the profile and calibration that are installed to my system without remeasuring the display using the “Create profile from measurement data” option?
Also, re-reading through BT 1886 info, I may just be confused and this may be the desired behavior after all. I think I was thrown off by the “Gamma 2.4,” where the targets on the verification chart are around 2.2.
Is this something I can also change for the profile and calibration that are installed to my system without remeasuring the display using the “Create profile from measurement data” option?
Not without doing a new calibration & profile, but note that the calibration tone curve only really affects non-color managed content (e.g. the desktop under Windows).
Also, re-reading through BT 1886 info, I may just be confused and this may be the desired behavior after all.
It is important to differentiate between “technical” (absolute) and “effective” (relative) gamma. BT. 1886 has a technical gamma (power) of 2.4, which when offset by the black level may result in an effective gamma that is lower than the technical one by necessity, and this is the desired effect.
Why do we choose a calibration tone curve of 2.2 instead of BT.1886 for desktop usage? Doesn’t the ReShade 3D LUT tone curve of BT.1886 for video games contradict this? Isn’t sRGB actually BT.1886 and only an approximation of 2.2?
Why do we choose a calibration tone curve of 2.2 instead of BT.1886 for desktop usage?
It’ simply the more commonly used target for legacy reasons. There’s nothing wrong with choosing BT.1886 (or sRGB) instead.
Isn’t sRGB actually BT.1886
Only under certain circumstances, i.e. if the contrast is about 1000:1.
When creating 3D LUTs for ReShade, shouldn’t the source tone curve be Gamma 2.2 since most games are sRGB and not BT.1886? Why is there to true sRGB preset in addition to Gamma 2.2?
When creating 3D LUTs for ReShade, shouldn’t the source tone curve be Gamma 2.2 since most games are sRGB and not BT.1886? Why is there to true sRGB preset in addition to Gamma 2.2?
With regards to games it really comes down to personal preference as there is no standard practice in the industry (other than the reasonable assumption that most of the graphics artists are probably using Photoshop, and probably work in sRGB, but whether their monitors are generally accurately profiled or not is a point open to discussion). For the ReShade preset I opted for BT.1886 as most games are created with video game consoles in mind as well, which are typically hooked up to HDTVs (and I can imagine the same to be true for quite some PC gamers as well, myself included, which use the big screen for gaming). For a typical 1000:1 contrast PC monitor, BT.1886 and sRGB produce a near identical result. The sRGB preset is there mostly for hobby photographers who shoot in sRGB and may want a better match in terms of tonality between color managed and non-color managed apps on their standard gamut monitors.
Sorry, I meant to ask why there is no sRGB source tone curve in the 3D LUT tab when the other tabs have both sRGB and Gamma 2.2. Should I just use Gamma 2.2 as the source tone curve instead?
Sorry, I meant to ask why there is no sRGB source tone curve in the 3D LUT tab when the other tabs have both sRGB and Gamma 2.2
Because it’s not a very common choice with regards to 3D LUTs, which are typically used for video applications. sRGB doesn’t play any role in the video world (other than sharing the Rec. 709 primaries).
Should I just use Gamma 2.2 as the source tone curve instead?
As I said, it comes down to preference.
