White Balance vs. Color Cast

[Kiran P]

Referring to the above statement, what exactly is the difference? And more importantly, does Whibal correct for this?

My gut instinct would be to say yes cause if lets say you're standing under a tree and have not only a slightly cooler color temperature because of the shade, but also a green color cast from the leaves or the light from the grass bouncing back at you, then by doing a custom white balance off the whibal, it should correct for this since there would be more green hitting the whibal. But why then do you have the option of still adjusting it furhter in C1 via the color wheel. I do notice as well that after setting my white balance by clicking on the first gray patch in the whibal cards, I get better neutral color by taking away some yellow. So can anyone.. espeically Michael, elaborate? Thanks.

Kiran

[MichaelT]

Kiran,

I do not believe in CWB if you are shooting RAW. In my opinion it is a waste of time and gains you (or me) nothing tangible in the end.

Shoot RAW. Hold the WhiBal as close to the subject of interest (face) as possible and when you do a click WB in CO the WB will be set correctly and this will remove any color case caused by the light.

If this is not correct and you have to correct further in CO, then perhaps your monitor is not calibrated and profiled correcty. The WhiBal is a pretty perfect device and cannot really be wrong. If you have an old one, it is possible that it is out of spec. We realized that the material was not as uniform as we were led to believe, so several months ago we began to measure each WhiBal individually to assure quality. Check to see if you have yellow lines on the short edge near the screw. That is part of the QC process and assures neutrality within our stringent spec. Also the later versions have a label to face the WhiBal towards the camera from a specific side. (When we measure we not only assure spec, but face the more closley spec'd side of each card towards the camera.

If you would like to send me a RAW file WITH the WhiBal in the shot i could comment further.

Use www.yousendit.com and send to image@whibal.com

[Kiran P]

I don't know why I said about doing a custom white balance because what I really meant was just doing it in C1 by clicking on the whibal with the eye dropper. So yes, I alway shoot RAW and never would otherwise.

As for my specific example, I can't dig up the actual file now. I've used my whibal in my 2 most recent sessions at the park as I'm waiting for the baby ducks to be born. I did notice that in one shot, I took two whibal pics seconds apart, one closer and one further away from the camera and the resulting white balance was different by 400K between them. Also, I do notice that by clicking around the first grey patch, I can usually get between 100K or even 200K difference in white balance values, but by then looking at the actual RGB values, this amounts to only maybe 1 or at most 2 values higher or low in the red or green color channels, so a difference of 100 or at most 200K doesn't seem to be that big of a difference in terms of white balance. I figure that in that shot though it might have been changing clouds that attributed to the different white balance values.

I guess I just wanted to make sure that if shooting under a severe color cast, would the whibal still be able to correct for this such as my example with heavy green in a picture as color cast and temperture of the light are two different things I would figure. But I did think all along that the whibal should correct for this. I wonder though, if you are in heavy green foliage and use your whibal and get a proper color temperature and eliminate the green color cast, could your colors still be off because as a result of the heavy green light, certain wavelengths of light were eliminted by the time they hit your subject and hence cannot be bounced off the subject into your camera lens? (ie. if the greenish light hitting your subject is deficient in red wavelengths of light, could your skin tones still be off since you would need the red wavelegths of light bouncing off your subject to properly show the pinkish colors?) (its all probably simple color theory but just please amuse me if you know)

Kiran

[JohnMalloy]

Kiran, in the situation you describe...overhead foliage with light entering on one side bouncing off grass, you could indeed have mixed light on either side of a face. And turning the whitebal cards toward one side or the other will give different results....

You need to decide where the primary light source is, there probably would be a color cast in the shadows...

[MichaelT]

To carry on John's comments further....

The cast thrown by the green foliage IS changing the color of the light hitting the face and will affect the picture and WhiBal WILL correct for this. But in mixed light, as John points out, you have to make a decision. Very simple to take a few WhiBal shots and then have a variety of references based on who the subject runs or is situated during the session.

Ducks or my morning Aligator. (I saw my first one in my backyard "lake" today, after seeing my first one in Florida over the weekend in a wildlife preserve (not a zoo).

I love to see this, my wife is not so happy, especially when I go out to get close and photograph :>)

[Vizual Groove]

Kiran,
In my ever elusive search for the perfect white balance, I often find myself doing the below in lighting scenarios like you describe.
I shoot the Whibal directly perpendicular to the camera in front of the main subject. I use this as my main wb correction and convert this iamge. I then use C1's wb dropper to analyze the surround areas and choose a point that better achieves a wb for the surroundings and convert this image. I then use a layer mask or 2 to blend the results. I have done this as many as 4 times with the same image to get what I wanted.
Sometimes it's just plain impossible to achieve really good results, even with such high end tools as the Whibal and C1. But, with methods like the above, you can even out the bumps.
Regards,
VG