sRGB vs Adobe RGB; 8-bit vs 16-bit

Discussion in 'Beyond the Basics' started by jamesino, Aug 31, 2008.

  1. jamesino

    jamesino TPF Noob!

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    If I am shooting in RAW with a Rebel XTi and processing the photos for online viewing only- no printing- should I be using sRGB or Adobe RGB colorspace in ACR 4.5?

    As well, should I be using 8-bit or 16-bit colourspace in ACR?
     
  2. Atropine

    Atropine TPF Noob!

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    Always sRGB if the photos are intended for the web.
     
  3. Helen B

    Helen B TPF Noob!

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    It's a choice between simplicity and versatility, and who your intended viewers are.

    sRGB all the way is undoubtedly the simplest method, if the images are for web only. In the past it would be a no-brainer. Two things are changing:

    Web browsers are becoming colour space aware, and

    Monitors are appearing with gamuts that exceed sRGB in certain colours.

    If you would like to have edited source files that will take advantage of those changes then it might be wise to work in Adobe RGB and convert to sRGB at the last stage for the moment. Many people will be perfectly happy with the gamut (colour range) of sRGB, so would feel no need to take advantage of future potential improvements, or they may be happy to go back to the Raw file and reconvert.

    16-bit vs 8-bit is a different issue. The choice is less about the capabilities of the final output device and more about the amount of tonal changes you are likely to do during editing. In simple terms a 16-bit conversion will stand more tonal manipulation without causing posterization (banding, gaps in the histogram) than an 8-bit file will.

    Best,
    Helen
     
  4. Garbz

    Garbz No longer a newbie, moving up!

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    Yep 8bit fine for viewing, not fine for heavy editing.

    The colour space comes down to you. What will you view it on, who is your target audience. If you are showing the photos on one and one only monitor then it depends on the gamut of the monitor. Wide gamut screens are approaching the sub $1000 market. If you intend to place them on the web it's a matter of tradeoffs. For the few people who use Safari to surf the web (IE doesn't support colour profiles, and firefox has them disabled by default and it's not trivial to enable), is it worth for the 0.1% of the world to see the photos that tiny bit better only to have the other 99.9% see them look like mud (literally skin tones go dark brown with incorrect AdobeRGB -> sRGB decoding).

    Also as someone who uses both the AdobeRGB space for my workflow (rarely for saving though), and who has a wide gamut monitor, let me assure you you are not missing much at all. I think I have shot a sunset, once where the AdobeRGB space actually made a visible difference, but unless I actively increase my saturation, nearly all of my photos don't benefit from the wider gamut, at all, not even in theory.
     
  5. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    They are also only appearing in certain income brackets. :) For the near future 99% of the web audience will be viewing monitors with a color space smaller than sRGB.
     
  6. notelliot

    notelliot TPF Noob!

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    +1

    and to add that personally, I'm in the same boat - rarely you see differences in S vs AdobeRGB. ProPhotoRGB would offer you a colour space almost as wide as the gamut of your eye, but it's useless for anything other than high-end solvent printers, like the new epsons.

    oh and, uh, my income bracket didn't hold me back from getting a wide gamut display. if you can't justify the price, chances are, you don't really need one :)

    ps - there's an HDR thread in there, why not a colour space thread?
     
  7. jamesino

    jamesino TPF Noob!

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    Thank you guys for the response. One last question:

    Does the RAW output of a Rebel XTi support 16-bit colours? It appears to me, I can just seamlessly switch between 8-bit and 16-bit colours in ACR at the bottom, but do my files actually have the 16-bits of colours to work with?
     
  8. Bifurcator

    Bifurcator TPF Noob!

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    The XTi is probably 12-bit and since there's no "popular" file format for 12-bit just save it in a 16-bit container. There won't be a full 16 bits of color fidelity at first but as you edit it the tween-tones will fill out the spaces - depending on the kinds of edits you do. If you save it as an 8-bit file you will be losing some of the resolution.
     
  9. Garbz

    Garbz No longer a newbie, moving up!

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    Forget the output look at the input. Grab your camera (with polariser to get even more saturation) go out take a photo, import the raw file as a ProPhoto file, then setup softproofing to sRGB, and hit ctrl-shift-Y to enable the out of target gamut warning.

    See all those grey pixels that indicate how much of the photo can't be displayed? Yeah me neither. Do see it very occasionally when shooting into a sunset though.
     
  10. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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  11. notelliot

    notelliot TPF Noob!

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    sure... but, if I need the extra range of colour, I'd work in prophoto. ie - in a club shooting a dj with all the neat lights. or digital cross process, sometimes. 80% of the time I use sRGB, sometimes prophoto or even lab is more appropriate for what I'm doin'. exactly as you say - look at the input.. that's all. :mrgreen:

    in the case of viewing on the web, that's a useless theory. but knowing about it doesn't hurt.
     
  12. Garbz

    Garbz No longer a newbie, moving up!

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    Yeah, although given a camera rarely outputs much better than AdobeRGB it may make more sense for that given the prophoto in it's wide gamut would put more of a strain on the bit depth.

    Actually I think i'll start a thread about this, explain it and see what others think.
     

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