[steve500]

I have stacked PL filters before, I don't know if they were just terrible quality, but when stacking I ended up with very very very blue photos. Do I need to do like a freaking super WB adjustment or do I need better filters?

[navcom]

Wheatfield may have the answer...use linear polarizers if you are going to stack them. Circular polarizers give strange color effects. Linears are created different than CP's.

[newarts]

A circular works by first filtering out the light from one polarization and then making the light mostly random (circular but not totally). If you put 2 circular front to back you get mostly nothing because the first one filters and there is not much the second filter can do. If you put the first filter backwards (front to front) then it will work like two liner polarizes.

DAZ

As Daz says the CPL farthest from the lens should be reversed. Remove the filter's bezel ring, turn the element over & replace the ring.

The color will likely shift as the ND effect is increased because the polarizers aren't uniformly effective across the visible spectrum; a custom white balance should fix this.


Iowa Dave

[newarts]

I just tried stacking a Sonia CPL and a Hoya linear polarizer (farthest from the lens). Minimum brightness was about 7.5 stops below maximum brightness when the polarizers were crossed. A custom white balance corrected the strange pinkish-purple color (k100D).

Actually, the crossed polarizers cut out the visible light & allowed the IR (and maybe some UV) to pass! In effect a variable IR pass filter. It seems to work pretty well as a near IR filter (like a Hoya R72) - I'll make some measurements.

Iowa Dave

[Robert S Donovan]

I have stacked PL filters before, I don't know if they were just terrible quality, but when stacking I ended up with very very very blue photos. Do I need to do like a freaking super WB adjustment or do I need better filters?

Mine were circular. You just have to rotate them to get them in the right "phase".