finding neutral gray

Discussion in 'Digital Darkroom' started by howard b. schwartz, Dec 31, 2009.

  1. i use the curves menu to do color correction. the white and black eye droppers are easy to use, however, i have trouble finding a neutral gray in every scene using the middle gray dropper. any way to find gray in all images. thanks
     
  2. Howard,
    There sure is. Get yourself a $10 Kodak gray card. Take a single picture of it in each lighting condition. Do whatever you do to it, and then do the exact same color correction by the numbers to every other picture taken in the same lighting.
    There are very marginally better neutral gray targets available for a lot more money; I’d strongly recommend starting with the Kodak card and saving your money unless and until you become dissatisfied with it — especially since it’s better than many (but not all) of the pricier options.
    Cheers,
    b&
     
  3. david_henderson

    david_henderson www.photography001.com

    Does this matter? What about the idea that you adjust the photograph until you like it/ until it looks like you recall it?
     
  4. A grey card will make life a whole lot easier, but there's another option if you're looking for a $0 approach:
    Use the info panel to read out the values for what should be a neutral midtone in your image.
    In the curves dialog, double-click the midtone dropper. Set the target values to either the R, G, or B from the info panel. Click that supposed-to-be-neutral area with the new settings, et voila—neutralized. The rub is that you have to have something that's supposed to be neutral. But if you don't, you're probably not going to this level of correction anyway.
     
  5. you can also use the auto button in the curve, by selecting the parameter before you will be able to use it to your liking. work 8 out of 10 times.. sometimes it give a very cold / green look to a image.. no perfect world ; )
    a gray card, a melita paper filter in front of your lens to do a custom white balance and many expensive gadget could also help before you loose too much time *fixing* image in post.
     
  6. Here's another 'trick' to try, which works optimally if there IS a completely neutral grey in the image. It works less well if there is not.
    • Create a new layer on top of your test image.
    • Go to Edit >> Fill and use 50% gray.
    • Change the Blend mode of this layer to Difference ~ (things will look ghastly now!)
    • Now, create a New Adjustment Layer with Threshold, and drag the slider all the way to the left (everything will go white now!), and then gradually move it to the right. The first areas that appear in black will be the neutrals. Nudge it more to the right to see a greater range of neutrals.
    • Mark those spots or areas with your Color Sampler tool if you wish, or just note where they appear, and there you have it.
    • Delete the two layers you created and you can now recognise the neutral areas in your target image.
    Have a Great New Year!
     
  7. When I started digital color correction many years ago, I also wanted to "find" the neutral tones and apply the eye droppers. More often then not, that would send me down the wrong path. Then I read Dan Margulis' book in which he talked about what are *true* neutral tones, how to *decide* whether they really exist in an image, and finally how to correct if they do/don't exist. That small section was worth the price of the book.
    A "true" neutral tone may not exist in our eyes even *before* releasing the shutter, e.g. a sunset that has a golden cast on everything, or a face lit by candle lights. In cases like these, including a gray card in the captured scene will not do any good. Nor will it make sense to digitally remove the *desired* casts by using an eye dropper, etc.
    OTOH, when shooting in a studio under controlled lighting, including a gray card would make sense. Such as when shooting products and preserving their true colors. Then digitally applying the eye droppers on the gray card in the captured images will quickly remove the *undesirable* casts from the studio lighting.
    But the vast majority of my images shot under natural lighting do not have any "true" neutral tones. More often than not, the seemingly "gray" pavement, the "white" cloud, and the "black" shadow are not "true" neutral tones. Once I apply an eye dropper to any of these, and if it happens to be not "true" neutral, it would be the beginning of a wrong path.
    BTW, these comments also apply to white balancing.
     
  8. Mike - Nice trick. I hadn't see that one before. For the reasons given by Robert, I wouldn't use this technique to help correct color, but rather, to check that after color corrections, elements of the image that are supposed to be neutral gray truly are, and are equally grey over their entire extent (if appropriate).
    I could easily see applications of this technique to product photography, modifying the method to check for colors other than grey.
    Tom M
     

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