Fun with Filter Factors

[madNbad]

Having been at this for a while, I was pretty sure I had a good grasp on how to figure filter factors. For quite a while I have been using a 022 light yellow filter and adding a full stop with either T-Max 100 or 400 plus the occasional Tri-X. Recently, I decided to kick things up a notch and added a 040 orange filter. Everything tells me to add two stops. For fun I decided to try these out on my M6 TTL, which is normally loaded with Portra 160. To my surprise when I added the yellow filter the difference was one half stop and with the orange one full stop. I also held the filters in front of my Sekonic 308s and found the same results. The M2 is used mostly for B&W and I normally reduce the box speed by a half stop. My negatives are processed at a local lab and they show good density. So the real question is, for my next roll, should I add two full stops with the orange filter or just one? Feel free to treat me like an idiot because as far as I know, the really aren't any stupid questions. Thanks for the help.

 

[Larry H-L]

The tricky part with color filters is that the results can vary depending on the subject matter.

If you photograph an all-blue or green scene with an orange filter, you will appear to have more of a filter factor than you would if you had instead photographed an all-orange scene with the same filter.

Similar colors to your filter pass through, while opposite colors are absorbed.

Tricky stuff in the real world of mixed colors. And filters vary by manufacturer.

Bracketing might be a good idea until you get the hang of it.