Does the selection of sRGB or Adobe RGB in camera when shooting RAW ever matter?

Question

In talking to a colleague of mine yesterday, we got onto the subject of color spaces in digital photography. He's a Nikon buff, I use Canon (specifically, an EOS 50D); I don't know if that is relevant to my question or not, but mention it for completeness.

I shoot RAW essentially 100% of the time, and have the in-camera color space setting at AdobeRGB (sRGB is also offered). The raw converter in turn is set to produce sRGB output files. As I understand the process, the general flow is for raw shooting: raw sensor data readout (including A/D conversion), compression, write to a raw file, then in post-processing rather than in-camera apply color space/color temperature/etc; for JPEG shooting: raw sensor data readout, apply color space/color temperature/etc, JPEG compression, write to memory card (in camera).

Hence, when he said that I should leave the camera set to sRGB for best/consistent results despite using the camera's raw format, it didn't really make much sense to me. I have mulled it over for a while now and it still doesn't really make any sense.

One of the answers to What is RAW, technically? seems to support my view of the differences in the data recorded in RAW and JPEG modes, respectively.

I did find What's the difference between Adobe RGB and sRGB and which should I set in my camera?, but the answers there seem to focus more on the difference between AdobeRGB and sRGB. My question is, when shooting RAW, does it ever matter (except for the image preview) whether the camera is set to sRGB or AdobeRGB? If it does, then why, and in what situations? Is my understanding of the "raw" format processing chain flawed?

Answer 1

The answer is basically the same as this one on white balance and raw. You're right, it doesn't matter at all in how the image is recorded or stored.

As you note, the selected color space applies to the preview image and to the histogram. The camera also may make metering decisions intended to avoid clipping (overexposing to the full saturation point) in particular channels, and that may be affected by choice of color space in-camera. I think this is less likely to be a real problem than having the white balance far off might be, though.

But I'd also take a careful look at the preview image in both modes. The rear LCD screen isn't something you can calibrate on most cameras. I think it's more likely that sRGB is correctly represented, and the screen might not cover the Adobe RGB gamut very well. (And really, I'd not be surprised if many cameras don't really handle preview display of Adobe RGB correctly at all — that's a lot more complicated than simply having the mechanism to save in that space.) I'd do some test shots and see which looks most like what your final printed output does, and then use that — that'll make the review screen more useful. It may very well turn out that an accurate display of sRGB is more like your final results than a bad rendition of Adobe RGB (even if you ultimately do use Adobe RGB in the end).