CIE Color gives uneven values when converting to BW

I found that when editing with CIE if I turn the image BW then the pixels do not retain a regular RGB value of (X,X,X) but that there is a cast, usually blue? Is this normal? How can I use the CIE colour features and still convert to a pure BW image?

ND7_0430.NEF (24.6 MB) | ND7_0430.NEF.pp3 (11.3 KB)

Using RawTherapee-dev-5.7-115-gb86b7a4-20190925.AppImage
Thanks in advance! Cheers

So I am not sure why; but I think I found a workaround:


If CAT02 Adaptation is unchecked and set to 100; the BW values are the same for R,G,B

CIECAM02 lies after the black-and-white tool in the pipeline. One way of looking at it is that converting CIECAM02’s output to B/W would undo the very effects for which it’s meant to be used. Play with the Viewing Conditions parameters to see what I mean.

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@Morgan_Hardwood the swift reply is very much appreciated. I played around in the meantime and it looks like if I set the Cat02 adaptation to 100 and uncheck the checkbox, it doesn’t mess with viewing environment compensation. I love most of the features in there otherwise.

Perhaps we should set this as such as default; and only have people change the viewing conditions settings if needed.

Cannot reproduce, the values are not R=G=B.

Setting CAT02 adaptation to 100 does not, and should not, result in R=G=B. That is not its job. Its business is to make the source image appear to look some way under some light. The source image may be R=G=B, but under some light it looks tinted orange or teal.

Every tool has an intended purpose, and every tool can be misused for other purposes, that’s fine. But the defaults should make the tool behave the right way for its intended purpose with minimal user intervention.

I’ve not played with the CIECAM stuff much, but I can imagine it being used to alter the colors in an image before converting to BW, e.g. to adjust the response to applying a color filter emulation in BW. I’m not sure though that CIECAM would have any advantage over simply adjusting exposure and white balance parameters since as mentioned this is not what CIECAM is intended for. If using CIECAM Stefan’s way is the intent, then the best way to do the BW conversion would be to save the CIECAM-adjusted color image as say a TIF and bring that back into RawTherapee to do the final BE conversion.

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yeah. and yet somehow I got it to work :stuck_out_tongue: I get that I’m being told it shouldn’t work; yet the artist in me wishes that there be a zero-saturation option as the very last step in the chain just for this kind of situation :slight_smile: