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Usefulness of color histogram?
I own a D200 which does have the color histogram, however I generally just check the main histogram to judge my exposure..

I guess I'm not sure what the color histogram offers me. For example, say I take a shot and look at the color histogram and red and blue look properly exposed but green is underexposed. What is this telling me? Should I bump up my exposure to better expose the greens while potentially blowing out the reds and blues? Or should I leave it alone?.

Is this just a "gimmick feature"..

Would the color histogram maybe point to a white balance problem?.

Any insight on this issue from those with more experience would be appreciated...

Comments (8)

The reason for a 3 channel [colour] histogram is simple.....

Whilst a luminance only (green channel) histo is usually perfectly adequate for exposure purposes, it is still possible for the blue or red channel to be clipped with no indication to the photographer until he gets back to the computer..

Blue clipping is notably rare, but red clipping (red channel overexposure) happens quite often shooting intensely coloured red blossoms..

The cure for clipping in any/all channels is to reduce exposure... and maybe add a tough of fill flash if shadows become clogged as a side effect.Regards,Baz..

Comment #1

Thanks, makes sense. One more question. Is the main histogram only made from the green channel as you described it as the luminance histogram?..

Comment #2

I thought the luminescence histogram had black to white on x axis and pixel count on y axis. never heard of green.

Buzzphotos wrote:.

Thanks, makes sense. One more question. Is the main histogram onlymade from the green channel as you described it as the luminancehistogram?.

Regards,Arun Sasidharan.

Home Page: http://www.asasidh.com.

Photos: http://flickr.com/photos/arunsasi/.

Blog: http://www.zenslr.com/..

Comment #3

If I can see that I've got the main data covered in all three channels (no cliffs on either side in any of the channels) then I feel pretty good about my chances in the RAW converter after the shoot. Shooting JPEG I tend to be more conservative with exposure and try to leave room on the right for the little tails that are hard to see..

With the bayer sensor I think there are twice as many greens as red or blue? I haven't seen that many green people so I think I'd rather have more reds and blues...

Comment #4

Buzzphotos wrote:.

Thanks, makes sense. One more question. Is the main histogram onlymade from the green channel as you described it as the luminancehistogram?.

Whilst a luminance histogram should record the light from all three channels there are twice as many green as red or blue photosites so recording luminance from ther green channel gives you a 50% sample..

I believe that is the method adopted by Nikon. It may well be the same with others..

To come back to the original question I would say that if you have a nice broad luminance "hump" at centre of the luminance histogram there is little or no need to check colour histograms..

Chris Elliott.

*Nikon* D Eighty + Fifty - Other equipment in Profile.

Http://PlacidoD.Zenfolio.com/..

Comment #5

Hartcons wrote:.

With the bayer sensor I think there are twice as many greens as redor blue? I haven't seen that many green people so I think I'd ratherhave more reds and blues..

Bayer sensors high green count emulates human vision's spectral sensitivity curve, which has a similar peak in the middle of the visible spectrum.Regards,Baz..

Comment #6

The luminance on my Canon seems to be a weighted sum of the RGB coordinates. For sunlight WB,luminance ~ 0.6 G + 0.3 R + 0.1 B.

A shot of pure red in sunlight results in the red histogram being about 1.7 stops to the right of the luminance histogram. If the histogram is from the green channel only, then the luminance should be well rather more than 1.7 stops below the red channel histogram. This should be easy to test in a given camera.Leonhttp://homepage.mac.com/leonwittwer/landscapes.htm..

Comment #7

You can also increase your chances of not blowing the highlights by switching to adobeRGB in the color gamut. adobe RGB is larger than sRGB and would have a little more room to hold data without blowing. this is especially true for jpegs..

If your dslr uses the jpeg settings for the histogram when shooting raw; it should also help that way as well...

Comment #8

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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