White Balance Question - Basic Goal?

[canoli]

I wanted to run this by you guys...


Should the RGB values in the in-camera channel histogram be as close to each other as possible? If they're identical (or close to it) does that mean I've successfully captured a neutral color balance?


I'm referring to evaluating white balance only, shooting natural light in an "average" scene, meaning there are no
predominant colors and no specific light sources that require compensation.


To put it another way, is equalizing the RGB values the goal when setting white balance?


Thanks in advance for any thoughts you'd care to share!

[canoli]

Is my question so completely obvious? ("Of course you should try to equalize the RGB values!")


If it is, sorry, but I'd still like confirmation if somebody would be kind enough to weigh in.


Thanks!

[Daniel Browning]

Should the RGB values in the in-camera channel histogram be as close to each other as possible? If they're identical (or close to it) does that mean I've successfully captured a neutral color balance?


If they're identical, and the object is gray, then you've achieved neutral color balance for a gray object. If the object is not perfectly gray, then the colors should not be close to eachother.



To put it another way, is equalizing the RGB values the goal when setting white balance?


Not really. The goal for neutral white balance is to equalize RGB values for neutral things (gray card, white objects, etc.).


Of course, if you shoot raw then you can change your white balance in post losslessly.

[canoli]

Thanks Daniel - I appreciate the response.



if you shoot raw then you can change your white balance in post losslessly.


So as long as you shoot RAW then it's not so important to get the WB "right" (closer than Auto at least) at capture?

[Daniel Browning]

So as long as you shoot RAW then it's not so important to get the WB "right" (closer than Auto at least) at capture?


It depends. There are several factors in play.


If you get the white balance right while shooting, it saves time later in post processing.


If there are no neutral objects in the scene, then it can be difficult to get a good white balance in post processing. For this reason I always try to include a shot of a gray card or white object (even a regular piece of paper) so I can get white balance at least pretty close during post processing.


For the ultimate color accuracy when shooting in lighting conditions with poor Color Rendition Index (CRI), like halogen, tungsten, fluorescents, etc., it may be necessary to shoot a color checker chart (XRite, Gretag McBeth, etc.) and build a custom color profile. But that's a lot of work.

[canoli]

Last question - Does the wrong - or "Auto" - WB setting interfere with metering? Is that a concern at all?

[Daniel Browning]

Last question - Does the wrong - or "Auto" - WB setting interfere with metering? Is that a concern at all?
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No. Metering is not affected at all by the white balance setting.

[WAFKT]

So as long as you shoot RAW then it's not so important to get the WB "right" (closer than Auto at least) at capture?






Correct, you can essentially shoot with your camera's white balance at any setting when shooting RAW (the image can look pretty bad on the LCD, so best to set the WB to the best preset possible (avoid Auto) so it at least looks passable on the LCD) - in post-processing you can define the correct white balance/colour temperature for your shots (with no impact on the image quality, when shooting RAW). But here's the catch; while you can correct the WB in post, you need some sort of reference for what would have been the correct white balance at the time you shot, in the lighting condition that you shot (or rather the light condition of the subject you shot). I know some people who attempt to do this by eye, or by sampling colour in a photo that they believe should be neutral, but I certainly don't trust my eye that much (as I've seen proof that my eye isn't that clever).


A white balance card(e.g. WhiBal or X-Rite Passport)is a quick and very useful way of getting this reference - take a reference shot with your white balance card in the scene for a given lighting condition (either before, after or in between your series of shots), and then use that image as your reference for correct WB for all images shot in that same lighting condition when you process your images through software (e.g. Lightroom, Adobe Camera Raw, DPP, Apple Aperture 2, etc...). The white balance card can be handy for dealing with situations where lighting conditions are changing while shooting - as you can typically shoot a quick reference shot much quicker than trying to set or change a custom white balance in camera. If I'm shooting in a condition where I know the lighting isn't going to change (much) throughout my shoot, I prefer to set the custom white balance in camera (using either a WhiBal or Expodisc, and save one step in post). This is an essential step if you're going to shoot Jpeg (still a useful format for certain kinds of shoots or if you have no desire to spend time in post) - while most photo editing software will allow you to change the white balance of even Jpeg images you're not necessarily getting true white balance across the entire light/channel spectrum - rather it's basically just overlaying a colour correcting layer filter to tint the image.


Note a while a traditional grey card may give you passible white balance, many of them are not actually neutral grey (their main use is for defining correct exposure by giving an 18% reference) and as such might not give you the best/most accurate white balance. If achieving the best possible authentic white balance is important to you, then best to invest in a product that is actually manufactured for providing white balance and verified by testing (I know each WhiBal and Expodisc are actually tested to ensure that they are as neutral as possible and those values are given).

[WAFKT]

Last question - Does the wrong - or "Auto" - WB setting interfere with metering? Is that a concern at all?






No. Metering is not affected at all by the white balance setting.






If extreme speed when shooting is important for you (e.g. shooting fast action sports or skittish wildlife) and you want to maximize your burst rate and minimize your shutter delay it's best to avoid anything "auto" (e.g. Auto White Balance; Auto Metering Modes - Full Auto, P, Tv, Av; Auto Focus; etc...). However, turning off Auto Focus might not be practical depending upon what you're shooting. In the end we're only really talking about milliseconds of difference - and likely not as significant on a Rebel vs. say on a 1D. But in certain shooting situations it can make the difference.

[canoli]

Thanks guys!


Much appreciated.

[peety3]

So as long as you shoot RAW then it's not so important to get the WB "right" (closer than Auto at least) at capture?
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One of the benefits of getting WB close to right up front is if you're using flash: getting the flash's white balance to match your ambient lighting. Fixing this in post is much tougher than just correction for auto or wrong WB with one/uniform ambient light source.

[SupraSonic]

RaW


AWB depends to adjust take a picture of a "WHITE PAPER" if the colour incorrect adjust the Kelvin and take a shot on people or scene or landscape if its too blueish adjust to a hiher number if its too brownish adjust to a lower number.

[Johnny Rasmussen]

May I also add that you sometimes can "blow" one of the colorchannels if you are shooting with a mixture of different lighsources, especially the red channel can be blown/clipped when shooting indoors with low colortemperatures. The WB presets could not prevent one of the channels to get blown/clipped. I needed to set a manual whitebalance to fix the problem. A reference card is a great solution.