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11/07/2007 01:23:09 PM · #1 |
From article here:
//www.ppmag.com/web-exclusives/2007/11/white-balance-the-secret-weapo-1.html
"Changing the white balance can and does darken or lighten the effective exposure of a file, thus potentially degrading shadow and highlight areas and the appearance of noise. When correcting cooler, bluer overall capture, the effective exposure increases. When an overly yellow image must be neutralized, the change is often noticeably negative."
This seems to make sense on some level. If you create overly warm image camera will reduce exposure not to clip the red channel. Will it?
Message edited by author 2007-11-07 13:23:14. |
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11/07/2007 02:01:52 PM · #2 |
it seems like a fairly poor example though - the original capture is already about a stop underexposed. No surprise that when he corrects it he then has to open it up by about a stop. (with the exposure and brightness tweaks)
Though in principle it is right - if you shoot a essentially yellow lit scene, then remove a lot of the yellow, you will get a correspondingly darker final image - most of the luminosity would have been in the red channel.
Same way if you shoot a mostly blue scene and then colour corrected the other way.
That's why you need to expose for the 3 RGB channels, not just the luminance channel, if you really care about all that.
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11/07/2007 02:47:49 PM · #3 |
The interesting part to me is the explanation of how Camera Raw's white balance adjustment is essentially using the same principles as working in LAB color. That explains a lot to me about why the interface is the way it is.
R.
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11/07/2007 02:56:39 PM · #4 |
I've thought that using a very warm light degrades the image because you are effectively using 1/3rd of your pixels (ie the Red ones) to capture more detail. At the least you are ignoring 1/3rd of pixels (the blue ones) as they have much less information encoded (and it's dark, noisy info). I've gotten away from using halogens and such because of this.
Can't promise that's true, but it seems like it should be so.
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11/07/2007 03:00:35 PM · #5 |
Originally posted by DrAchoo:
I've thought that using a very warm light degrades the image because you are effectively using 1/3rd of your pixels (ie the Red ones) to capture more detail. At the least you are ignoring 1/3rd of pixels (the blue ones) as they have much less information encoded (and it's dark, noisy info). I've gotten away from using halogens and such because of this.
Can't promise that's true, but it seems like it should be so. |
though it's actually 1/4 red and 1/4 blue pixels on a typical sensor, anyway. So the issue would be more pronounced. 1/2 the sensor is green photosites.
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11/07/2007 03:30:13 PM · #6 |
Originally posted by Gordon:
Originally posted by DrAchoo:
I've thought that using a very warm light degrades the image because you are effectively using 1/3rd of your pixels (ie the Red ones) to capture more detail. At the least you are ignoring 1/3rd of pixels (the blue ones) as they have much less information encoded (and it's dark, noisy info). I've gotten away from using halogens and such because of this.
Can't promise that's true, but it seems like it should be so. |
though it's actually 1/4 red and 1/4 blue pixels on a typical sensor, anyway. So the issue would be more pronounced. 1/2 the sensor is green photosites. |
Yes, thanks Gordon, you are exactly right. I just mistyped.
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11/07/2007 03:38:31 PM · #7 |
| Hmm - photos taken with my new flash equipment just seem much better than under tungsten lighting... And this presents a pretty good explanation as to why. Interesting. |
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