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Hi there everyone,

I'm going to start a topic that will hopefully start a conversation regarding something I thought of while lying in bed last night (....keep reading, it's not what you think!!! )

When adjusting white balance in RAW or when the camera does it in firmware... doesn't it just add (for example) more blue to the image to balance the picture colour? If that's the case wouldn't that increase noise in the blue channel (especially at high ISO's)

... If one used a filter to do this optically before the light hit the sensor wouldn't that help lower the noise?

I could be totally off wack here... It was just a thought I had.

Anyone have any opinions/ideas? I'm sure I will be shot down in the first reply

Paul

BANG

Seriously though, you could have a point.

... Unless you need to go to a higher ISO due to less light reaching the sensor after you place the filter in front of the lens.

Is this the kind of filter you mean?

http://www.expodisc.com

It allows you to get the white balance correct before you shoot.

I believe Sheetshooter raised this issue before his foray into digital... I can't find the thread now, but you're right Paul, an optical filter will help to reduce noise in the colour channels - but in practical terms it's probably not worth bothering with. If you are game to try, I believe the 80 series filters are the ones you'll be after - eg. 81 warming, 85 cooling, etc (just going off on the filter numbers in PS CS2 - presumably corresponding to the optical equivalents).

This issue probably has more merit and deserves further consideration when shooting under artificial lights with a colour temperature wildly different from daylight, and also under high ISO.

Essentially, adjusting white balance is trimming the levels of blue and red with respect to green in an image. Raising ISO is increasing the levels of all 3 colour channels' response, signal and noise proportionally increased indiscriminantly.