colour spaces and camera raw

clintham · 7 Apr 2010 at 00:35

im pretty good in photoshop, but with camera raw im a little confused as its relatively new to me.

my camera is currently set to shoot sRGB in raw format.
when i open a CR2 file in camera raw its default its default space is adobeRGB - 8 bit.
my monitor is set to a sRGB icc profile.

seems theres a lot of differences going on here and i must be making a stupid mistake. surely these areas should be using the same profiles.

also in camera raw i see i have the option to select:
- colourmatch RGB
- prophoto RGB
- 8 or 16bit
- picture size up to 25mp

so heres my (noob) questions:
1 - should i set my camera to adobeRGB as it has a wider colour range when compared to sRGB?
2 - should i change to prophoto or colormatch in camera raw?
3 - should i change to 16 bit in camera raw?
4 - if i use prophoto (for example) is there a profile for my monitor to match?
5 - if i select a picture size larger than the native 12mp my camera takes, what will happen to the image qulaity?

i have done some reading around these topics but it just seems to confuse me further - hopefully the ocuk community can iron out a few things

clintham · 7 Apr 2010 at 14:01

anyone?

Messiah Khan · 7 Apr 2010 at 15:23

so heres my (noob) questions:
1 - should i set my camera to adobeRGB as it has a wider colour range when compared to sRGB?

Depends on your output really. I would generally stick with sRGB unless you know it is intended for print where you can take advantage of the wider gamut. Also as the camera LCD will be unable to display the full gamut of AdobeRGB you may end up getting gamut clipping when trying to review your images.

2 - should i change to prophoto or colormatch in camera raw?

Prophoto has a much wider gamut than both sRGB and AdobeRGB so if great to work in. However when it comes to outputting to either a printer or for the screen, you will need to convert to a narrower gamut profile or you will end up getting gamut clipping. So yeah, while you are working in a colour managed space such as Photoshop or Lightroom, then there is no reason why not to work in ProPhoto, although it may be worth softproofing to the colour space you intend to output to.

3 - should i change to 16 bit in camera raw?

Generally you will be fine sticking with 8 bit unless you have a specific reason to go with 16bit colour. Whereas the gamut of a colour space increases the range of colours you have to play with, the bit depth increases the number of colours you have to play with. the main common reason you would want to use 16 bit is if you have very subtle tonal graduation of colour (say a sky fading from dark blue to slightly lighter blue) and there aren't enough colours available to display the subtlety of the graduation. In this case you may end up getting banding or postarisation so you would benefit from 16 bit.

Having said that, if you shot your image in 8 bit, then you will not benefit at all from changing the image to 16bit, unless you dither the colours. So to get the benefit of 16 bit colours tyou will need to shoot in 14bit RAW (unles you camera supports 16bit raw files, which I think only digital MF cameras do to date.)

4 - if i use prophoto (for example) is there a profile for my monitor to match?

Your monitor will be unable to display the gamut of Prophoto. To get the correct colour, you need to hardware calibrate your monitor to create a custom profile. This is the number 1 thing to do in order to achieve accurate colours. You can however 'softproof' your image to a narrower gamut colourspace or profile (such as a paper profile) to see what it would look like.

5 - if i select a picture size larger than the native 12mp my camera takes, what will happen to the image qulaity?

Where is this? In Camera RAW? If so it will just upscale the image. You don't gain any detail but it may allow you to printer bigger etc. Personally I would stick with the image in it's native resolution all the way through the processing and then scale it up/down at one of the last steps in your workflow.

Hope this helps.

clintham · 7 Apr 2010 at 15:37

thanks, thats really helpful. i think i had overread about a few areas and it had me in a daze.
im not doing anything wrong in my current workflow which is a relief. i realise that was a bit of a bumper post and a little technical too. thanks for taking the time to reply - much appreciated

Adrianr · 7 Apr 2010 at 16:10

RAW files don't have a colour space. You have to set one on your camera because it asks, but your sensor will capture more colour than either sRGB or Adobe RGB can display and that information is held within the file regardless. You only choose a colour space for a file upon demosaicing (developing) where you also specify bit depth. Lightroom has a working colourspace of ProPhoto RGB by default but I'm not a fan due to far too many unknowns (it's too big for any monitor or output device IMO).

My answers to your questions (no more or less right than Messiahs just my workflow)

1. If you're shooting RAW it's irrelevant.
2. I develop my RAW files into the Adobe RGB colour space. It allows me to include more of the colours my camera can capture (than sRGB) but still within the realms of my monitor (most importantly) and doesn't require as much clipping for most output devices (less importantly).
3. Depends pretty much on two things. How much post production you do and how good your computer is. 16bit files are twice the size but will allow you more leeway in manipulation later on. I have an exclusive 16bit workflow because my computer can handle it and I want the highest quality retouched files. (You can always change a 16bit image to 8bit for output later but not the other way around).
4. Not even remotely close I'm afraid! Though ProPhoto does actually fall outside the visible spectrum in areas so also never will be.
5. Sometimes uprezzing at the demosaicing stage can be a good idea. However with programs like Genuine Fractals and Alien Skin Blow Up these are almost always superior for upsizing files. Infact I know of not one RAW developer that's better, so I'd say don't bother.

Basically, your camera can capture a lot of colours, your monitor can display less, and most output devices display even less still. Its good practice to have one bad-ass master file that you can then make lesser derrivatives from for various output devices. As my monitor can nearly display all of the Adobe RGB gamut I'm happy working in that colour space as I know there are no nasty surprises. If it's going to a narrow gamut printer I can take time softproofing with the master file to get the most from the print file. The method I now work with has basically lead to no surprises at any stage from capture to output (Though my monitor has been one of the single largest elements in achieving this).