Custom White Balance or CC Filter?

[don_bryant2]

<p>I've just read a brief article on the net suggesting that exposures made under incandescent lighting will be less noisy if a CC filter is used instead of Custom White Balance or AWB.</p>

<p>I've never tested that idea, has anyone out there tried that?</p>

<p> </p>

[alan_bryant1]

<p>Probably true, for the blue channel anyway. If you examine the red, green, and blue channels independently for photos taken in incandescent light at high ISO, it's not hard to see the blue is noisiest.</p>

<p>On the other hand the CC filter steals a lot of light, so you might have to boost the ISO to compensate, re-adding the noise you were trying to remove. But, if you're working in a studio on a tripod with stationary subjects, that isn't a problem.</p>

[g dan mitchell]

<p>Assuming you are shooting digital, in which case you should simply shoot RAW and adjust in post. Use a gray/color card if you need to capture a reference for later adjustments.</p>

[alan_bryant1]

<p>G Dan, even when you shoot RAW the blue channel will be noisier when you balance for incandescent lights.</p>

<p>Basically you're underexposing the blue by about 3 stops, then boosting that channel in post. And you know that a 3 stop exposure compensation in post will significantly increase noise. It is not difficult to see; load up an image in Photoshop, look at the red, green and blue channels separately.</p>

<p>Not that I use CC filters. They're a pain to use, and for almost all work a little noise in the blue is irrelevant. But it is there.</p>

[joe_fikes]

<p>All other things being equal, low light situations are noisier than situations with plenty of light. I haven't tested the idea, but I suspect that adding the filter will add noise to the image.</p>

[phule]

<p>CC filters are useful when the light is heavily saturated in one color and your exposure times don't really matter so much (i.e. no subject movement).</p>

<p> </p>

[stwrtertbsratbs5]

<p>You can either boost the blue channel with a custom WB, or you can use a CC filter to drop the red and green channels down to the same level as the blue. I'd expect that boosting a single channel would be less noisy than dropping all the channels down.</p>

[michael_young3]

<p>I recently tested an 80A filter under tungsten lighting. The filter has a very slight and almost visible (possibly not entirely imaginary) improvement in noise. I would expect larger improvement from the 1 1/3 stop of ISO speed eaten by the filter. That is, if you can afford to slow the shutter from 1/60 to 1/20 for the filter, you should see a larger noise reduction by simply decreasing ISO the same amount and shooting without the filter.</p>

<p>I'll try to post some detail crops later. It didn't occur to me to shoot the slower ISO shot as a test control until after. Will have to shoot them again.</p>

[phule]

<p>[[i'd expect that boosting a single channel would be less noisy than dropping all the channels down.]]</p>

<p>You'd only be dropping them down if you kept the same exposure time and underexposed the image. </p>

 

[stwrtertbsratbs5]

<p>"You'd only be dropping them down if you kept the same exposure time and underexposed the image."</p>

<p>That makes no sense, unless you plan to make dark muddy prints.</p>

[g dan mitchell]

<p>Fair point about the blue channel potentially being the noisiest channel. But as the reply to my message pointed out... the difference isn't going to be that significant and the noise isn't likely a problem anyway.</p>

<p>But, yes, if you are sure of where you want the color balance to go the filter could get you there in "pre" in stead of post.</p>

<p>Dan</p>

<p>(You could also use one or another NR technique on the blue channel - or the whole image - in post. Six of one and a half dozen of the other in the end, or maybe 5 of one and 7 of the other. I'll leave it to you to decide which is which. :-)</p>

[sarah_fox]

<p>I've thought about this before, and I think you're right about the CC filter being a lower noise solution. However, that's only true if you don't have to bump your ISO to compensate for the lesser light. If you have plenty of light, then yes, that would make sense.</p>

[phule]

<p>[[That makes no sense, unless you plan to make dark muddy prints.]]</p>

<p>My point is, Robert, that the levels would not be dropping down. The levels would be equalized and the exposure time would be increased.</p>

[stwrtertbsratbs5]

<p>Filters remove light. So what you are doing with a CC filter is reducing the amount of red and green light that hits the sensor, so you'd have to increase the ISO (assuming that you are shooting at a particular shutter speed and aperture for a reason). Alternatively you could make the exposure without the CC filter at a lower ISO and increase the gain on the blue channel. That's likely to be less noisy than shooting at a higher ISO and increasing the gain on all three channels.</p>

<p>Where are all of the scientists and engineers?</p>