Strong ND filters.

[ann]

Lee"s Big stopper won't give you a color shift, but they are hard to come by as it is a small company.

what you are seeing is very common with ND filters.

[E76]

Also remember that if you are using the ND filter in order to give long shutter speeds (>1 sec) the colours of your film will alter due to reciprocity failure. This is more likely the cause of the problem rather than the filter itself. To test my theory, shoot two exposures on a DSLR (one with the ND filter and one without) If the colours are the same then it's not the filter (remember to turn off AWB). If you don't have a DSLR, try and do the same test on your film camera but make sure the shutter speed stays below 1 second with the filter in place i.e. do it in bright light with a wide aperture and on fast film if necessary.

E100G has a cyan color cast with very long exposures (over 120 seconds) and not a magenta one. I'd place the blame solely on the filter.

[rayonline_nz]

Since I am so uncertain may get it when I am overseas and can test before paying...

I have a dSLR - the B+W 6 stop does have a warm cast, so does the 2 stop but slight. Yep, shot in daylight WB, not auto.

The one above linked in the picture is film shot well under reprocity limit and it was a 4 stop Hitech. Got a refund but they allowed me to keep the filter.