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Hello Florian,
using the program “ICC Profile Inspector” I noticed that the tone reproduction curve does not correspond to that of eciRGB_v2 when set to L*. Which is strange because the eciRGB_v2 curve corresponds to L*. I don’t think it has anything to do with the black output offset option, does it?
I attached two screenshots. The first curve belongs to the eciRGB_v2 color space and the second curve to the monitor profile after calibration at L*. As you can see, they are quite different.
Thank you very much for your great work!
Egor
Hi,
In your example screenshots, it doesn’t look like you have calibrated to L*. I would also recommend to use the DisplayCAL curve viewer or profile info, as it’ll be much easier to compare tone response curves there (ICC profile inspector just plots the curve as it is encoded, i.e. relative luminance Y, while DisplayCAL offers you the choice between Y and L*, with the latter being the default, thus highlighting the differences in the graph much better).
I noticed that the tone reproduction curve does not correspond to that of eciRGB_v2 when set to L*. Which is strange because the eciRGB_v2 curve corresponds to L*.
Real displays tend to have a non-zero black level, so the curve is offset by the black level. eciRGB_v2 on the other hand is a synthetic (working space) profile, that has a zero black point.
I’m sorry Florian, that was my mistake.
The monitor is calibrated to L*, but I have chosen “XYZ LUT + reversed matrix” for the profile type. Thus the sRGB curve was written into the TRC-tag.Thank you for helping!
Egor, I find it interesting that you are using L* as a target curve for a monitor. May I ask in what context you use it? (just curious to know).
Hi Pneumatic,
usually it makes sense to select the same tone reproduction curve for calibrating and the color profile of the image. Thus you can achieve a smoother tone reproduction, at least in theory. That’s because in this case, each brightness value in the image becomes assigned to the same brightness value in the monitor.
I often use eciRGB_v2 as color profile. It has an L* curve. So I calibrate to L*.
How well it does work in practice, depends on the monitor, the measuring device and the software which is used.
Thanks Egor, that makes sense.
Am I correct though in presuming that you are using eciRGB_v2 for some kind of content creation (photography, printing etc.), and at some point later in the chain the content itself gets converted back to sRGB/2.2 or whatever the intended final display is? Just trying to understand as I’m not a colour professional and have never used colour managed workflows.
You are welcome, Pneumatic.
Converting from eciRGB_v2 to sRGB is only necessary for non-colour managed workflows, e. g. presentation of images on the internet. Apart from that eciRGB_v2 is a common working colour space like sRGB or AdobeRGB. When I print images by myself, the workflow is fully colour managed. Even if I order pictures from a printing service provider, I make sure that their workflow is also colour managed. So my images can stay in the eciRGB_v2 colour space.
The reason for using eciRGB_v2 instead of sRGB is that sRGB is a relatively small colour space. If there are saturated colours in the image, you will soon reach the limits of sRGB.
I also could use AdobeRGB instead. This colour space is larger than sRGB too. But the colour space coverage of my monitor is better suited to eciRGB_v2.
