RAW Output Color Space/Camera Colour Profile

[tomczak]

If the Camera Colour Profile in RAW Options is set to None, and the Output Color Space is set to say AdobeRGB, what exactly happens? How does the PWP RAW know the source (i.e. the camera) colour profile to then convert it to AdobeRGB or sRGB if it's not provided with one? There is also a Camera Space option - what space is that?

Then, when RAW gets processed, the image is tagged with the Working Colour Space - has the data conversion taken place, from PWP RAW Output Colour Space to the PWP Working Colour Space, at the end of the RAW processing chain?

The related question regards Camera Colour Profile. I don't have profiles for my particular cameras, but I found several generic once for these models. Using any of those profiles as Camera Colour Profile in PWP RAW produces pretty weird colours and tones. Even more interestingly, each generic profile, for the same camera, produces vastly different image. I recall the Forum discussing the camera profiles in the past, but I'm not sure what the consensus was on using Camera Profiles in PWP RAW and which profiles to use, if any?

[jsachs]

There is no such thing as a generic profile - a profile is only useful for a specific image capture protocol, so you need to know exactly how the reference image that the profile was created from was captured. Any change in the procedure (such as lighting, exposure, raw settings, etc.) invalidates the profile since the profile's job is to take image input to a particular color space.

[tomczak]

That was my understanding too. I was curious how the PWP RAW process can label an output image as having a certain ICC profile even if it doesn't know much about the gamut of the camera that produced that RAW (i.e. no camera profile)?

[jsachs]

This feature is provided for those who have the capability to create a custom camera profile such as you could generate using Profile Mechanic - Scanner.

[tomczak]

What I have trouble understanding though, is what happens in the RAW workflow if there is NO camara profile. It still allows for the output image to be produced/tagged? with an ICC profile.

How does PWP RAW know what colours it produces as an output if it knows nothing about the input camera gamut?

[jsachs]

If there is no profile, it looks like the raw output is just tagged with the working color space and no conversion is done.

[tomczak]

One more thing that bothers me. In RAW Dialog: Options/Advanced Settings/Output Colour Space there is a choice of 4 output spaces: Camera, sRGB, AdobeRGB and WideGamut. Choosing any of them produces different outputs, yet all the outputs are labeled with the Working Colour Space.

So each of the four RAW identical outputs was arbitrarily tagged with one of the 4 colour spaces chosen by the user in RAW (btw. what's 'Camera' space?), then converted to the Working space?

[jsachs]

It turns out dcraw has coefficients built into it also for each camera that define the color gamut so the raw data can then be converted by a matrix multiplication to sRGB or some other color space.

[ksinkel]

You should set your raw color space to your working color space unless you are using a camera profile. If you are using a camera profile, then you should use the same color space as was used in making the profile. This is documented in the Help for Raw Settings.

So just to recap, since this has been an extended posting:

The image is converted to the chosen raw color space using specific information for each camera model. If a raw profile is specified, it is corrected using the profile and it is then displayed in the working color space of the system. If no profile is used, it is displayed in the working color space directly. This is why you should use the working color space as your raw color space when you are not using a raw color profile. Other choices of a raw color space will result in needless additional conversions.

Kiril