I've been thinking about this kind of image for a while now and tried shooting it today, but I got a weird result and I was wondering if anyone more experienced could shed some light on what is happening...
The scenario is this:
- Daytime long exposure - 2 min @ f/22, ISO 200
- Filter stack - 24-70mm f/2.8 -> UV filter (too lazy to remove) -> 10 stop ND filter - Thin CPOL
- All filters are B+W and have no visible defects
- CPOL is set to max, as far as I know. I did a test a while back and aimed the camera at my computer monitor and adjusted it until I couldn't see the screen. I then marked the rotation on the CPOL with a permanent mark. I line up the marks, I should, technically have the 'maximum effect' of the CPOL.
- Composed and took the shot to see what effect I got and whether it matched what I thought I would get.
So the 'problem' is the vertical band of light about 1/4 in from the right side of the image, where there is a glow and clear delineation of the CPOL effect (grass is more less reflective, sky is more blue, etc.)
Did I hit the CPOL and knock it out of alignment (I don't think I did, but I didn't check thoroughly at the time because I didn't see the problem on the camera view screen)? Should a CPOL not be stacked in this fashion? Should a CPOL not be used for long exposures? I've not run across anything saying one way or the other.