A "Definitive" filter factor guide?

[matthew blais]

I have a Hoya filter book, have looked at Tiffen's and Lee info and there seems to be (albeit slight) discrepencies between all these for the (essentially) same filters. I know it realtes to variables such as light source, film response, etc. But is there one source that most of you find to be "as good as it gets"?

I'm starting a large LF project and trying to put a field note (dummy) kit together-laminated book of all the stuff I so easily forget.

I'll be shooting FP4 and HP5 for B&W and also some trannies, but am not going to use anything but a PL for that.
Your help is appreciated.
Matt

[Nick_3536]

"(essentially) same filters"

Depending on the filter it's because they aren't the same. IIRC the Hoya Orange [G] is supposedly a #15. Well that's not going to match a Tiffen Orange filter. The Tiffen is going to be a #21 or at the very least a #16. The #15 is a dark yellow even if Hoya calls it orange. Tiffen uses the Wratten system. Hoya I think uses the German system for filter numbering.

Either accept the filter factors they give you or do some testing.

[ronald moravec]

Same as Nick wrote. Test by photographing a grey board under the same conditions you will use the filter. Next open the aperture based upon the filter factor and bracket using the aperture only. Find a frame where the board is the same density. That is the filter factor under those conditions with that film.

I have done this with filters that have unknown factors and it has worked perfectly.