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Correcting a Color Cast


Rich54

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I came across this photo with an extreme green color cast that I tried to correct (see second attachment). However, aside from setting the black, white and mid-tones, it's not clear what any of the other colors are truly supposed to be. Even though my "After" photo seems reasonably ok, how do I know if it's correct? For example, the arm bands on the referee are a pinkish color. Is there any way to know if that's right?

Here's a quick summary of the steps I took:
1. I selected the offending shade of lime green and applied a photo filter using the opposite color. That got rid of most of the color cast.
2. I used curves and levels adjustments to set the black, white and middle-gray points.
3. Applied a Shadows & Highlights adjustment.

Before.jpg

After.jpg
 

hawkeye

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It looked a bit washed out, especially the faces. I just used a curves adjustment and set a grey point
 

Attachments

  • Untitled20150926095928.png
    Untitled20150926095928.png
    471.7 KB · Views: 2

Rich54

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Thanks. I like your method better than mine. (Pink didn't seem like a color associate with ice hockey, so I suspected mine was off.)
 

Tom Mann

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Rich - You were absolutely correct when you said that it's not obvious what the colors really should be. This isn't a matter of lack of photography or photoshop technique, but is a fundamental limitation caused by the physics of the source of light used. That hockey rink was almost certainly lit by mercury vapor lights. The problem with them is that almost all of their light output is concentrated in a single, extremely narrow band in the green-yellow part of the spectrum, with almost no broadband emission like one has from sunlight, strobe lights, tungsten lights, etc.

Below is an example of what the image might look like if there was absolutely no continuum emission at all -- just the one spectral line. Try to use the color eyedroppers on this image, and you'll find that you can't recover any realistic colors at all. This is simply because there IS no other color present, just that one single green-yellow hue.

The bottom line is that when faced with a situation like this, one either should convert it to grayscale, or do what Hawkeye did, and try to get the most pleasing colors you can by what amounts to a purely ad hoc method based on what little "real" color is present.

Tom M
 

Attachments

  • Before-tjm01-ps01a_no_possibility_of_cc-01_698px_other_green.jpg
    Before-tjm01-ps01a_no_possibility_of_cc-01_698px_other_green.jpg
    226.8 KB · Views: 14

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