filter factors: measuring them using a lightmeter?

[HT Finley]

I didn't read all the posts, but I can tell you that after exhaustive work on learning exposure meter calibration and repair, that meter sensitivity to different colors is all over the place. In fact it is so undependable, I've about reached the conclusion the the Zone System itself is a haphazard process, and that I may as well just use incident readings. Reading through a colored filter would be a wonderful thing, but unfortunately meter cells are so non-linear in their color response as to be hopeless for that. All you can really do is just use the filter factor that is typically printed on the edge of the filter ring. Remember, the filter factor charts commonly seen are based on Kodak Wratten filters. A Vivitar or Hoya 25A or K2, or X1 may not be the same as the Wratten. So in the final analysis, Use the best information you have, but don't depend on a meter to help you determine filter factors. I've learned that lesson good.

[LabRat]

I agree the biggest differences from metering B/W through filters is the film's spectral sensitivity and prevailing color on the scene... If you are in red-orange sunset light, or deep blue, your film/filter/meter will see it differently, and what mood/contrast/time of day/and color brightness (lower/higher key?) etc are you after???

Your experience (and previous testing) comes into play here...

But I have backed off using filters for some time now, as I prefer to let the image render in it's natural form on B/W, and that filters tend to be a two-edged sword for what you gain here might make other issues there, and things like tuning development is a more uniform way to generate a "style" of image formation (and I'm tired of a filter "look" to "choke" and predominate an image)...

Steve K

[Drew Wiley]

Filters do not have to be used blatantly. They can do subtle corrections too. A good magician never shows his hand. I almost never goof a filter factor, despite working with a lot of different films and owning a lot of different filters. Right now I've got 8X10 holders loaded for deep RGB in-camera separations, just in case I stumble onto suitable subject-matter. But even a third of a stop error in that case would be way too much. So don't tell me it can't be done precisely.
After awhile, you hardly need to think about it.

[John Layton]

I must say that I agree with Drew...that after awhile its not too much of a stretch to use filters with some consistency and precision. Also...with regard to comments about "overexposing for safety" - while I might, when photographing unfiltered, tend to give a more generous exposure if I'm feeling particularly protective of deep shadow detail (maybe placing important shadow details on zone 3.5 instead of 3)...I'm actually typically a bit more stringent while using a filter - particularly a red or orange, as I find that such a raising of values (while filtered), with or without development compensation, can visibly "dial back," the desired effect I'm seeking.