Walt Wayman wrote:
> But to the point: Why not just make the correction in post processing. The
> effects of an 81A filter should be easy enough. I've got bunches and bunches
> of filters, but I don't use any, except polarizers, for digital since it's so
> easy to mimic the effects in either PWP or PS.
>
The 81 series are one of two types of filters whose effect cannot be
fully duplicated in post. The other one is, of course, the polarizer and
its ability to control reflections.
At any altitude reachable in Georgia, and indeed the East Coast, you are
correct. At the altitudes Wayne shoots at in the Bolivian Andes, UV is
very high level. The problem is that the blue sensors in the camera or
film can't differentiate between UV and visible blue light. So when you
correct the excessive blue in some parts of the subject, it throws off
the color balance in the other parts.
Some shots can be corrected nicely in post. Others, even with masking of
different areas of the image, can be very difficult to make natural
looking. I tried that on a couple of Wayne's images when he first posted
some from Bolivia with problems a few years ago. After all those
discussions, he started using 81 series filters, which nicely fixed the
problem.
Interestingly, if one is always going to post process ones images, it's
better to use too strong an 81 filter than not strong enough. Over
filtering makes sure there is no UV effect and the other color balance
problem is easy to correct.
I've just looked at the lens on the F30. What I would do is buy some 81
a or b gel filter(s), cut out appropriate sized circles and carry a
little baggie of them and a roll of double stick tape. The gels are
cheap and each piece should be usable several times. There is a big
enough circle of metal surrounding the actual lens opening to do this in
a way that won't interfere with the lens opening and closing.
If one happens to be left on for an indoor or other shot, flash or not,
where it over warms it can easily be corrected in an editor.
Moose
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