Manual White Balance - how to?

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Hening Bettermann:
Hi!

Even though I am happy with AWB, that is without comparison, so I want to investigate. I wonder how to use manual white balance.

1-how do you expose the white card, for zone VII or VI? (I remember that in connection with camera profiling, in some context we are advised to pick WB from the second-whitest patch of the ColorChecker, not the whitest)

2-Which WB do you set for the shot of the White Card? Auto, or the nearest, e.g. cloudy ? (I think of daylight only; and of a WB I would use in post-processing; for a transition, I would like to compare manual to auto WB)

3- A product like the ExpoDisk by ExpoImaging, Inc.
http://www.expoimaging.net/product-overvie...ywords=ExpoDisc
looks like it might be handier to use than a white card. Does anybody have experience with it?

Thank you for your response!

Panopeeper:
Quote from: Hening

I remember that in connection with camera profiling, in some context we are advised to pick WB from the second-whitest patch of the ColorChecker, not the whitest
The point here is not to use a raw clipped patch, as that would be misleading. ACR does not allow picking WB on a patch containing saturated pixels, but I think most cameras do not care for that (see your Uni-WB template).

Quote

Which WB do you set for the shot of the White Card? Auto, or the nearest, e.g. cloudy ?
This plays no role. The shot of the WB card can be used either as a WB template in-camera, or for picking WB on it in raw processing. The WB of that shot is irrelevant in both cases.

It is possible that you misunderstood something in this relation, and that may be the reason for the strange WB coefficients with your neutral WB template. However, this is speculation on my part.

Quote

A product like the ExpoDisk by ExpoImaging, Inc. looks like it might be handier to use than a white card. Does anybody have experience with it?
I don't have experience with either; thus only a remark: make a distinction between the color temperature of the source of illumination and of the scenery. For example I live at the ocean, the coast is mountainous with forests. The setting changes the illumination, depending on the direction you are shooting, for the open water and the forested mointain side reflect the original illumination differently. Thus, measuring the color temperature of the sunshine (or cloudy sky) does not show the actual illumination of the surrounding scenery.

DarkPenguin:
Quote from: Panopeeper

I don't have experience with either; thus only a remark: make a distinction between the color temperature of the source of illumination and of the scenery. For example I live at the ocean, the coast is mountainous with forests. The setting changes the illumination, depending on the direction you are shooting, for the open water and the forested mointain side reflect the original illumination differently. Thus, measuring the color temperature of the sunshine (or cloudy sky) does not show the actual illumination of the surrounding scenery.

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

This reminds me, I need to buy a whibal.

Panopeeper:
Quote from: DarkPenguin

Being under a forest canopy is a problem, too.  Where do you point it?
Let's go one step further: is this kind of WBing always useful? I mean, does an object, which reflects all visible light waves equally (i.e. it is "white" or "grey") have to look white in all settings?

When in the Lower Antelope Canyon, in Arizona, I shot a white card for later WB. When back home, developing the raw images, I tried to WB them based on that shot. The result was horrendeous. Although the resulting color matched the sand (we took a tiny amount in a small plastic bag), it did not resemble at all the scenery as I saw it, because the entire canyon inside was not lit by the "original" sunshine but by the reflections on the walls. Ultimately, I WBd based on my memory.

When shooting in a night club or bowling alley or other place, where the illumination is intentionally unnatural, like black light, should one WB so, that a white shirt become white? That would ruin the mood. I admit I have no idea how such a shot should be WBd if not purely subjectively.

Hening Bettermann:
Yes we are into a theoretical problem here. In principle, I want to maintain the color of the light and not filter/wb it so everything looks like shot at 6 500 K. So when I started shooting digital, I took a purist approach, set the camera WB to Daylight, and did not change that. However, images taken on a summer evening under an overcast sky, looked really TOO blue-green. So I fell back on AWB. It gives satisfactory results - without having a comparison. What I am really after is the  "theoretically correct" color.

Gabor, as to my not-so-uni WB: I don't think this can stem from a misunderstanding from where to pick the WB. I did not use an eyedropper in this connection. The fact that my Kodak White Card is a specimen which has seen better days could not possibly cause such a gross bias??
---
>The point here is not to use a raw clipped patch, as that would be misleading. ACR does not allow picking WB on a patch containing saturated pixels, but I think most cameras do not care for that

So this would indicate to expose the White Card for zone VI if one plans to use it for post-processing.

Good light!

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