Filter Factor

[Jerry Cunningham]

I purchased a used yellow Hoya filter. It is marked Y(K2). Does anyone recall what the filter factor is on that item?
Thanks,
Jerry Cunningham

[Robert Ley]

Filter factor of 2, one stop increase of exposure.

[Jerry Cunningham]

Thanks Robert

[Andrew O'Neill]

It can also depend on what film you use. I never follow published factors...they are general numbers, like factors for reciprocity effect.

[Helen Bach]

A Wratten 8 (K2) has about 90% transmission over most of the spectrum, so you can use less than one stop, depending on the effect you want.

Best,
Helen