Manual White Balance - how to?

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Jonathan Wienke:
Quote from: Hening

What I am really after is the  "theoretically correct" color.

There is no such thing. You can use a white reference (Color Checker, WhiBal, etc.) to achieve a reasonably close color match between the original subject and a print, but that is of limited aesthetic use. Outside of catalog, documentary, and forensic photography, the color cast of the lighting is usually an important part of the visual appeal of the image. Portraits are commonly "warmed up" (intentionally given a slight yellow-orange color cast relative to "colorimetrically correct") to make the skin tones more attractive. The same is often true of landscapes shot at sunrise or sunset--compensating for the lighting so that whites are R=G=B neutral usually neuters the character of the lighting and makes the image appear flat and dull. Deciding how much to allow the coloration of the lighting to skew whites & grays from neutrality is a judgment call made for creative reasons. If it could be consistently calculated by a formula, camera AWB would have been perfected decades ago.

Wayne Fox:
Quote from: DarkPenguin

Being under a forest canopy is a problem, too.  Where do you point it?

This reminds me, I need to buy a whibal.

I assume you mean an expodisk?

A common mistake with the expodisk is to just slap it on your camera and point it at the scene.  to be used correctly the camera must be facing the same light source that the scene is.  For example, if shooting a portrait sitting or still life, you place the camera where your subject is and point it to where your camera will be.  If shooting a scenic, you normally turn around and shoot it in the opposite direction.

The challenge in a landscape is often where you are standing the light is nothing like the light of your scene.  Of course, this is challenging for both an exposdisk or a whibal chard.

Personally I find using a card much simpler.

Panopeeper:
[quote name='Wayne Fox' date='Jan 1 2009, 02:56 PM' post='248617']
For example, if shooting a portrait sitting or still life, you place the camera where your subject is and point it to where your camera will be.  If shooting a scenic, you normally turn around and shoot it in the opposite directionQuote

I don't have any expodisk, but my understanding is, that you need to shoot the light source; that may come from the direction of the camera's position, or it may not.

Guillermo Luijk:
I know what WB is and I know how to adjust it to obtain the desired results. But still there is a question I ask to myself from time to time: what's the reason for needing different white balances depending on the colours present in the scene to get a natural result, if those colours also changed in-place when our eyes where looking at the scenes?

For example, if I develop a landscape with a 'Daylight' WB preset, the result looks good. If now I go indoor, switch a light on and shoot again, why do I need to do a proper tungsten WB to obtain natural colours? why the Daylight preset produces an orange unreallistic appearence on my image? the camera doesn't lie, it just captures light on a tri-band RGB basis. Why the channel alignment (WB) that was fine for the outdoor landscape produces a natural result to my eyes, but need to change to a tungsten channel alignment (WB) to get the same feeling my eyes had being there?

The only answer to me is the way our brain works, performing by itself some kind of WB or temperature compensation. In the tungsten scene the light was really very orange, like the camera captured it, but our visual system involuntarily corrects it to make it appear more 'natural'. If we develop the indoor scene with Daylight white balance and look at it, our visual system will not correct it since our environment prevents us from doing it.

What do you think?

BR

Hening Bettermann:
I think your description is right. We might add that the WB of our brain does not work 100%. You DO see the sunset (or the rise, if you're up that early;-) ) as red. An empirically based definition of the theoretically correct color would have to measure the distance of the human-brain-WB from physical white throughout the spectrum, and for a lot of people. This is for the landscape photographer, for  whom the color of the light is part of the subject, unlike the catalog photographer, who may achieve his goal with a white card.

Individual differences may be considerable. I would suspect that the difference is less for a trained (naturalistic) painter than for a person whose memory is leveled down by only seeing images which are tailored to cater for this memory.

Good light - of any color!

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