Lately I’ve been examining the color cast created by the ND filters I own.
I have a beautiful Singh-Ray soft grad 0.9 that was given to me as a gift years ago and a set of Formatt Hitech 0.6, 0.9 and 1.2 which I use primarily for strobe work.
Granted the Formatt’s are resin CR-39 instead of glass but they permit me to open my aperture for shallow DOF with the slow flash sync speed of the Pentax.
I have notice a small amount of magenta color cast while using them as such but never found it to be too overwhelming to clean out in post.

Formatt ND0.9 with Yongnuo IV Speedlight

On a shoot a couple of months back I tried to stack the Formatts to achieve a 7 stop ND effect.
Wow, was the color cast dense. So heavy I couldn’t pinpoint a spot with either LR or PS Raw to achieve a natural WB.
Looking on the web for ND color cast I came across a review for the Ice ND1000 by a fellow Pentaxian which showed minimal casting between the image shot and corrected.
When B&H listed the P series of $49.95, I decided to give it a try. If I didn’t like it I wouldn’t be out that much.
While I haven’t used it much, I’ve been pleased with the results so far. It is made of optical glass and feels much like my Singh-Ray in build quality, one to take care of for long life

Ice ND1000 + 1.3 stop circular polarizer

Spectator during the shoot 1.3 stop circular polarizer

Decided to try an experiment to see how my filters compared to each other for cast by brand.
I kept as many constants as possible: tripod, f8.0, ISO 100, 50mm focal length and WB set in camera to 5500k.
In LR the as shot WB showed as 5300 temp and -16 tint (slightly to the green) on all photos.
I chose the exact same point (mid grey rock) in each photo to achieve the WB correction and will list the difference with each photo. Continue reading →