Flower color accuracy problems

Discussion in 'Digital Cameras' started by Chris Malcolm, Aug 27, 2012.

  1. I've been struggling with my camera's tendency to get flower colours
    wrong where blue purple and magenta are concerned (Sony A550). Not in
    any consistent way. Sometimes blues come out purple, sometimes purples
    come out blue. It's partly that auto white balance gets it wrong when
    the flower bloom fills the image. Using a gray card to set white
    balance improves things. It's partly intense colours getting
    overexposed -- reducing exposure helps.

    So by way of experiment I've been photographing flowers in the garden,
    processing and printing them, and then taking the print out to the
    garden to compare it with the flower. I was stunned to discover that
    my latest careful methodology had produced a blue print of a very
    obviously pink Morning Glory bloom.

    But wait a minute! I was sure I remembered the flower being blue!
    Could it be changes in UV radiation?

    It turns out that some Morning Glory flowers change from blue to pink
    during the course of a day. And back again. Hm...
     
    Chris Malcolm, Aug 27, 2012
    #1
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  2. Chris Malcolm

    Peter Irwin Guest

    That would seem very likely to me. One way to check would be to use
    an effective UV filter. If you have a Kodak 2A gel or a Tiffen 2A
    filter one would almost certainly fix the problem if it is the UV
    content that is causing the problem. (These filters have a slight
    yellow colour to them, but are known to be completely effective
    against UV. The fact that you can not tell a good UV filter from
    an ineffective one by looking can be a problem because some things
    sold as UV filters nowadays are sold for "protection" and the makers
    do not expect the customer to care whether they filter out UV or not.)

    Peter.
     
    Peter Irwin, Aug 27, 2012
    #2
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  3. Chris Malcolm

    Martin Brown Guest

    It is a side effect of getting flesh tones exactly right. They
    deliberately bury all the residual errors in the line of purples.

    http://en.wikipedia.org/wiki/Line_of_purples

    You have to be unlucky about the choice of plant but some do really mess
    up slide film - much less so on digital CCD imaging.
     
    Martin Brown, Aug 27, 2012
    #3
  4. But some flowers are notorious for photographing pink because of UV
    while appearing blue to the eye; wild gentians of Switzerland are a
    spectacular example.
     
    James Silverton, Aug 27, 2012
    #4
  5. Chris Malcolm

    Robert Coe Guest

    : >
    : > But wait a minute! I was sure I remembered the flower being blue!
    : > Could it be changes in UV radiation?
    :
    : That would seem very likely to me. One way to check would be to use
    : an effective UV filter. If you have a Kodak 2A gel or a Tiffen 2A
    : filter one would almost certainly fix the problem if it is the UV
    : content that is causing the problem. (These filters have a slight
    : yellow colour to them, but are known to be completely effective
    : against UV. The fact that you can not tell a good UV filter from
    : an ineffective one by looking can be a problem because some things
    : sold as UV filters nowadays are sold for "protection" and the makers
    : do not expect the customer to care whether they filter out UV or not.)

    I'd expect flaws in the glass to be a greater problem with cheap filters than
    failure to block ultraviolet. Most cheap glass doesn't pass ultraviolet well.
    Two examples: Hospitals and nursing homes buy (or at least did the last I
    knew) special UV-passing glass for their sunrooms. And photochromic sunglasses
    don't work well in automobiles because the windows filter out most of the UV,
    and it's UV that makes the glasses darken.

    Bob
     
    Robert Coe, Aug 29, 2012
    #5
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