> I hope to shoot digital next year and will probably white balance in situ
> rather than in "post."


Hi Shangara.

Not having but some 1-2% of your knowledge and expertise in Photoshop, I
never thought I could  offer you a piece of advise, but this one I can tell
with absolute confidence.  Custom white balancing, as boring as it sounds,
( requiring to shoot a 'calibration shot" with every change in lighting) is
the only way to keep the chip under control. Those new cameras offer auto
setting for daylight, tungsten,fluorescent,flash etc, devised to ease your
life, but those "canned" settings have such a big range of color
temperatures, you can't tell if you are really calibrating anything at all,
and then the fight occurs in PS, when you could have none or just a little
at all.

 It is the equivalent of having many different emulsions of the same film,
and even some different films for the shooting, so some changes can be
expected to happen in color rendering. Well, just the same. Auto White
Balance  can go  from 5000k to 6600k and the camera makes the choice on a
shot by shot basis.

White balancing is like choosing the same  film and emulsion for some
specfic shooting. I suffered from this problem while reproducing   some 120
Paintings for a catalog. Most of the images were shot on day 1 and 2 with my
custom WB routine run before shooting. Days later I was in a frenzy ( in
another asignment) and some few paintings were to just arrive and leave the
studio in minutes. I set my lights, resembling the original set, went into
AWB in the camera , did the shootings and the paintings were delivered back.

Then , as things happen here on and on, the final layout of the catalog took
longer than expected ( those graphic designers....), and then there was not
a chance to make any corrections in the printing stage. Everything went
straight on to litography and press. I did not have the slightest chance to
get involved in the CMYK conversion and it was the GD himself ( not the
press) who did it.
When I saw the printed catalog, I was most impressed with the results, with
the clear exception of those paintings shot on Auto WB. Absolutely no
relationship at all with reality. I was able to stand on the Gallery,
catalog in hand, checking one by one the results, and I could not believe
how nice those calibrated images matched the paintings and how awful the
other (Auto)  group printed.
With All things equal, I can only blame this on the WB miscalibration.
Of course some post proc would have solved it, but it did not happen.

A very basic, but useful set up for AWB and exposure , involving both a
Kodak Grey Card and and white card can be seen at

www.luminous-landscape.com/tutorials/dig-exp.shtml

I have exchanged some e-mails with the guy who wrote it ,since I questioned
his sequence,( he runs AWB first and then the grey card) and suggested to
run first the Grey card to adjust exposure via the camera histogram, before
shooting the white card .
He agreed that it is more precise to go my way,  but insisted that results
may be the "almost" same in both cases( some people claim AWB can be set
with the very same grey card anyway), but, as we are talking about fine
tuning, it makes sense to be as strict as possible during pre- shooting, and
having less trouble in post-processing.

   All the best.

  Jorge Parra
   APA/ASMP
www.jorgeparra.com 

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