After having bought a CP filter (see other thread with help & warnings ) last week, I've also tested it finally. I was on a hike in the mountains, and basically had it on the camera all the time just to check what it would do and what not.
It did some nice things - suppressing reflections, darkening the sky to keep the exposure of both earth and sky correct - and one not so nice thing: It introduced a heavy color cast when set to darken the sky (not in all images, but in many). Which was bad because images looked very strange & needed a lot of PP, and good at the same time, because the green of the trees looks very vivid (I often suffered from the problem that conifers look very dark & desaturated before).
Anyhow, is this normal for a CP filter? My semi-scientific explanation would be that the blue light from the sky is partly polarized, and by filtering part of it away (to darken the sky, for example), I'm left with a "surplus" of orange light causing the color cast...
Polarizers can indeed be very handy, as you've discovered. In the mountains where there is less scattering due to dust and other particulates, the light is is already slightly polarized. I rarely use a polarizer at high altitude because the results can be somewhat unpredictable. And with 4x5 I can't afford unpredictability! When I do use one, I adjust the polarization very little. Another thing that happens is shadows will tend to darken, since they are lit by the blue sky.
Discussion
3 repliesAfter having bought a CP filter (see other thread with help & warnings
It did some nice things - suppressing reflections, darkening the sky to keep the exposure of both earth and sky correct - and one not so nice thing: It introduced a heavy color cast when set to darken the sky (not in all images, but in many). Which was bad because images looked very strange & needed a lot of PP, and good at the same time, because the green of the trees looks very vivid (I often suffered from the problem that conifers look very dark & desaturated before).
Anyhow, is this normal for a CP filter? My semi-scientific explanation would be that the blue light from the sky is partly polarized, and by filtering part of it away (to darken the sky, for example), I'm left with a "surplus" of orange light causing the color cast...
Any ideas, hints, comments?
Basil
Polarizers can indeed be very handy, as you've discovered. In the mountains where there is less scattering due to dust and other particulates, the light is is already slightly polarized. I rarely use a polarizer at high altitude because the results can be somewhat unpredictable. And with 4x5 I can't afford unpredictability! When I do use one, I adjust the polarization very little. Another thing that happens is shadows will tend to darken, since they are lit by the blue sky.
-PB
Basil
Kent in SD