What to use for 18% neutral gray card?

Discussion in 'Digital Photography' started by DeanB, Mar 28, 2007.

  1. DeanB

    DeanB Guest

    Do people actually buy neutral gray cards for doing color corrections?
    If so, where do you get them or what do you use instead?

    Photoshop has a color correction function where you can point the
    cursor onto such an object and it will correct the color cast for you.

    Thanks

    Dean
     
    DeanB, Mar 28, 2007
    #1
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  2. No. They use neutral white things. Such as WhiBal.

    http://www.rawworkflow.com/products/whibal/index.html

    (I don't use this and don't know if it's any good. Just throwing it up as an
    example. Any neutral white object will do.)
    FWIW, 18% gray cards aren't for color correction, they're for exposure
    measurement. Kodak makes them. But they should work.

    http://www.kodak.com/US/en/motion/products/tools/card.shtml

    Or: http://www.amazon.com/Kodak-Gray-Cards-Pack-8x10/dp/B00009R7B0
    Yep. But I never like what happens when I click on those things.

    David J. Littleboy
    Tokyo, Japan
     
    David J. Littleboy, Mar 28, 2007
    #2
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  3. DeanB

    Jim Guest

    You can buy 18% gray cards at photo stores.
    Or, if you don't have a photo store handy, you can just use grass.
    Jim
     
    Jim, Mar 28, 2007
    #3
  4. DeanB

    Bert Hyman Guest

    (David J. Littleboy) wrote in

    Kodak does provide a technique for using gray cards in color
    correction at

    http://www.kodak.com/US/en/motion/products/tools/cinematographer.shtml

    "When the lighting does not match the color balance of the film."
    and
    "When lighting consists of different color temperatures."
     
    Bert Hyman, Mar 28, 2007
    #4
  5. DeanB

    King Sardon Guest

    Cool! Kinda messy holding up a wad of turf, though. And possibly all
    that green color might throw off the white balance.

    KS
     
    King Sardon, Mar 28, 2007
    #5
  6. DeanB

    DeanB Guest

    You mean you've never seen David Bailey holding up a chunk of turf
    with his Olympus Trip?
     
    DeanB, Mar 28, 2007
    #6
  7. They work fine for colour correction if the grey is colour neutral.
    Kodak's cards, for example, are deliberately made to be colour neutral.
    (That may mean they use a carbon black pigment rather than a dye when
    printing them).

    And a grey card can sometimes be better than a white card. If the
    gamma of the cyan, magenta, and yellow images in the negative don't end
    up being properly matched, you can make either whites or mid-greys
    neutral, but not both at the same time, when printing. Making grey
    neutral is probably better because most of the scene is nearer to grey
    than white.

    This probably doesn't matter for image captured directly by an
    electronic sensor.

    Dave
     
    Dave Martindale, Mar 28, 2007
    #7
  8. DeanB

    Alfred Molon Guest

    I bought mine in a photo store in Munich. It's colour-neutral grey.
    Yes, see here for instance:
    http://www.molon.de/galleries/Morocco/Merzouga/Misc/img.php?pic=1

    Here I used the grey card to measure the colour of the sand of the
    desert.

    Here I measured the colour of the stones of the pyramids in Gizeh:
    http://www.molon.de/galleries/Egypt/Pyramids/img.php?pic=10
     
    Alfred Molon, Mar 28, 2007
    #8
  9. Hell no! We all go to Home Depot and swipe a 1.5" stack each of gray and
    white paint sample cards. These things rock!
    Getting things right in-camera is a lost art in this day and age. Some
    people feel they can just tie a dSLR with a VR/IS lens to the end of a rope
    and swing it around for Photoshop pot luck.







    Rita
     
    =?iso-8859-1?Q?Rita_=C4_Berkowitz?=, Mar 28, 2007
    #9
  10. Critical changes are better made on a large screen than on the 2.5 inch
    things on the camera.

    Or, are you talking about making corrections "automatically" using the
    cameras software? That is even worse.

    Get the best you can with the camera sittings and then perfect in PS.
     
    Ockham's Razor, Mar 29, 2007
    #10
  11. Neither. He's talking about measuring the light and color correctly and
    getting it right before shooting.

    For exposure, this maximizes the dynamic range of your captures. (Look up
    "expose to the right" on Luminous Landscape.)

    For color balance, you can also improve the dynamic range of your captures
    by using color correction filters. But very few people do that with digital.

    David J. Littleboy
    Tokyo, Japan
     
    David J. Littleboy, Mar 29, 2007
    #11
  12. Huh? I think the goal here is to achieve and practice good photography
    technique. This means properly using the camera.
    I think we both are really saying the same thing. Good technique minimizes
    post time.





    Rita
     
    =?iso-8859-1?Q?Rita_=C4_Berkowitz?=, Mar 29, 2007
    #12
  13. DeanB

    John Sheehy Guest

    They should be rectangles, not points; the slightest bit of noise can throw
    everything off with a point-click.


    --
     
    John Sheehy, Mar 29, 2007
    #13
  14. DeanB

    John Sheehy Guest

    (Dave Martindale) wrote in @swain.cs.ubc.ca:
    There are basically two points of non-linearity possible with digital
    cameras. One is in the highlights; the estreme highlights can be non-
    linear due to starined amplificatio



    --
     
    John Sheehy, Mar 29, 2007
    #14
  15. DeanB

    DeanB Guest

    I got the WB presets to work on the camera - basically photographed a
    white piece of paper in a preset-recoring mode, and then used that for
    white balance. The results were outstanding - under simple tungsten
    light the pics came out as in beautiful daylight, and when bouncing
    the flash off the ceiling, there was no color cast I could perceive.

    White paper was used, as pointed out by David above, that's what it
    says in the book.

    Thanks all!

    Dean
     
    DeanB, Mar 29, 2007
    #15
  16. DeanB

    JG Guest

    Excellent.

    I have been waiting for an excuse to use recreational soft drugs to
    enhance my photography......

    John
     
    JG, Mar 29, 2007
    #16
  17. Yep, the old piece of white paper generally works out really well most of
    the time if you know your paper is really white. Most paper looks white to
    the eye, but it really is some off shade of white or other color. Your
    camera will see white differently and adjust. Try a few different samples
    of copy paper and you will see differences in WB values.







    Rita
     
    =?iso-8859-1?Q?Rita_=C4_Berkowitz?=, Mar 29, 2007
    #17
  18. DeanB

    DeanB Guest

    Alfred - do you use those pics when you get back to photoshop, or do
    you use them to correct the color balance for subsequent photos on
    site?
     
    DeanB, Mar 29, 2007
    #18
  19. DeanB

    Alfred Molon Guest

    In this specific case I wanted to know what the colour of the sand was
    and used the grey card as a reference.
     
    Alfred Molon, Mar 29, 2007
    #19
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