[Jewelry making - Article 00916] - Re: [Orchid] Photographing Jewelry 101

[Alberic]

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Hi Lois:

    Your bleached out photos were more likely the result of a mismatch
    between your working colorspace and the colorspace for the web. The
    web's default colorspace is sRGB, which is the most restrictive of
    the various common RGB colorspaces. This means that there are RGB
    colors that your camera can record that cannot be defined within the
    sRGB space. It also means that when photoshop converts from your
    camera's files, it must compress the color range to fit within
    sRGB's boundaries. Imagine you had a picket fence with 100 pickets.
    If you build the fence to fit a yard 100 feet wide, you'll have 1
    picket per foot. If you then move, and take your picket fence with
    you, and the new house only has a yard 25 feet across, you'll have to
    either throw away pickets, or compress them so that they're only 3
    inches apart. Photoshop can do either one, and frequently a little of
    both, to convert between colorspaces. The end result is less dynamic
    range in your image. 

    The thing to remember is that once you've thrown away data to fit
    into a tight colorspace, you can't get it back if you move into a
    wider colorspace. You can fake it reasonably well, the first time,
    but after that, you're cooked. 

    RAW images don't really have a colorspace, they're just the raw RGB
    data from the chip, so they can be converted into any space with no
    loss of quality. (in primary conversion from the raw file. Mess with
    the working file after that, and you start losing data.) 

    What I normally do in Lightroom is leave it set to ProPhotoRGB.
    ProPhoto is the largest possible RGB colorspace, so it's less likely
    to clip image data. Failing that Adobe RGB is the next largest. So I
    leave my master images set to the largest colorspace possible, and
    then downsample from the master images on a case-by-case basis,
    depending on what my goal for the daughter file is. For the web, I
    usually go down to sRGB, and turn off the ISO profiles, or set it to
    a generic. 

    Oh, that may be another issue: ISO profiles. They're an imbedded bit
    of data that {theoretically} tells the displaying computer what the
    color response of your generating computer was, so that
    {theoretically} the displaying computer can adjust itself to
    simulate what the image looked like to you when you were making it.
    Generally, most home PC's have the system installed wrong, so all it
    does is foul things up. Turn them off whenever you have the
    opportunity. 

    As far as reducing the size of the image (downsampling) reducing
    color, no, not exactly. Digital files aren't like film. You do loose
    detail and thereby clarity, when you downsample, but the colors stay
    at full intensity unless you're downsampling to the point of
    uselessness. I'm a little concerned about your 40K files. That seems
    *awfully* small, even for web images. If you're using JPG compression
    to get a decent sized image smashed down to 40K, the real culprit may
    be your compression settings. For serious work, I wouldn't use
    anything less than 70% (or 7) quality. If you're down under 50,
    you're causing problems for portfolio images. (Web buttons, yeah,
    sure, but not real images.) 

    HTH,
    Brian Meek.

    PS--> Much as I hate citing wikipedia, it is a good spot for generic
    info that nobody has cause to cant. they've got a pretty good set of
    articles on colorspaces, as well as a good comparison image of
    various RGB colorspaces. The image is here: 

    http://en.wikipedia.org/wiki/Image:Colorspace.png
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