> That difference in how the digital sensor sees the natural world has
> been a real pain in this exercise. I'll experiment with that white balance
> later after I get this preset business done with.
But the color sensitivity isn't uniform with B&W films. Zones I-III of
many B&W films will have different color sensitivity than IV-VI and
VII-IX. This is where a program like Sfx goes the extra mile.
> The colour filtering provided by Exp6 is convenient, but it only
> provides for a particular band of colour at a time (so it seems), which is
> not consistent with most Wratten filters. Many of the green filters will
> perform this way, but the majority will filter out increaing amounts of
> yellow to red (blue filters) or orange to blue (yellow, orange, and red
> filters). This complicates matters and requires that some generalised form
> of filtering that can be customised be brought to bear.
It's even more complex than you'd expect.
Take the Wratten #8 filter. Yellow. You'd expect the yellow filter in
digital monochrome conversion would work the same. It doesn't. It
actually acts more like a a #12 (minus blue) filter if the source
image has predominant red, green and blue spikes on the histogram.
When the color spectrum of the source image is narrow banded to the
three primary colors, a "minus" filter is very effective. However, in
the real world, blue skies are rarely exactly blue.
--
Ken Norton
ken@xxxxxxxxxxx
http://www.zone-10.com
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