Re: Using 89B Infrared Filter with Regular B&W films

[boblong@xxxxxxxxxxx (Robert Long)]

On Tue, 11 Feb 1997 07:09:15 GMT, Sue Myers wrote:

|I just shot a roll of T-max myself, for my photo project for a Graphic
|Comm. class I'm taking. . . I have a cokin red filter (#3?) which is the
|equivalent of a Wratten 25, and the shots I took with the filter look =
very
|similar to those taken w/o the filter. I took them last Friday, on an

This post, plus the earlier similar comment, is very puzzling to me.
Perhaps that's because I've never tried using T-Max films for
landscapes, but it certainly goes against the grain of both
conventional wisdom (is that an oxymoron?) and my own experience with
regular panchromatic films.

According to "the books," panchromatic films render the visible
spectrum more nearly the way we see its values than do orthochromatic
emulsions (which are notably weak in the red range), but pans still
don't have the hypersensitivity in the yellow-green that the human
retina does.  The recommended "correction" is usually a light yellow
or yellow-green filter.  A dark yellow filter goes beyond correction
to make deep-blue skies look a little darker, and therefore more
dramatic, than they do to the eye.  An orange filter is supposed to
take this tendency a bit farther, a light red filter a bit farther
still.  By the time you get to pan film with a Wratten 25 (dark red)
filter, the effect is supposed to be "very dramatic," partly because
it's blocking off the blue light in which shade and shadow areas tend
to be rich, and thus yielding "increased contrast."

In my experience, all this is pretty true.  Certainly I'd never
confuse any landscapes I've done using a red (25) filter with outdoor
photographs made with no filter at all.  And the spectral curve of
T-Max doesn't suggest a mechanism that might make its behavior
signficantly different from that of regular pan films.

Bob Long
(boblong@xxxxxxxxxxx)

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