I think I've been having some issues with my 4x6 size Singh-Ray 5 stop ND filter. I seem to get a pink/purple or red color cast whenever I use this filter (the severity depends on the original skyl.
Here are some examples of just using a Singh-Ray ND grad, ND Grad plus 5 stop ND two shots and then right after with just the ND grad again. NOTE: I didn't bother cloning out the marks from the dirty sensor.
Anyone experienced this In this particular case the differences in exposure were about 2 sec expoures without the 5 stop Grad filter and 30 seconds with the filter. It was too windy to get a reflection, so I thought i'd use a ND filter for the water.
I ended up with a lot of color cast across the top, which Initially thought might have been bcoz of moving clouds, but there is no way that there was that much movement that there would be a color cast over the entire sky and part of the peaks. Moreover, I also experienced this with much shorter exposures in the past. I also found that if i switched to my ND Vari-ND filter, i wouldn't have an issue. The problem is the Vari-ND is to too thick (i have slim version), to use with ultra-wide angle lenses.
Does this look like a quality control issue - should I be calling Singh-Ray