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.
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
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.
Singh_Ray soft grad ND0.9
non corrected 5300 temp & -16 tint corrected 5301 temp & -16 tint
Formatt Hitech ND1.2
non corrected 5300 temp & -16 tint corrected 5293 temp & -6 tint
non corrected 5300 temp & -16 tint corrected 5295 temp & -3 tint