Contamination?

[Mike Wilde]

By the way, I think the expired filters that you have might be the first generation ones. They came with a calculator dial, to figure the exposure change for swapping filters.

The second (current) generation has neutral density built in that allows one exposure for 00-3.5, and twice the exposure for 4.0-5.0.

[Anthony J. Martinez]

They had a table inside, but yes I have the new filters now and the exposures seem pretty straight forward.