need help for filter factor

[riton mhilli]

Hello all
I can't fix the exact filter factor of my Ukrainian yellow green filter in combination with efke R25 and R50.The factor engraved on the filter ring is 1,4X nearly a half stop.This factor doesn't give me good results, may be,due to spectral sensitivity of the film.Generally the negs are very thin.Your help is very appreciated.Thanks

[Peter K]

A yellow-green filter needs al least a filter-factor 3 with a panchromatic film, but 4 is a good starting point to make test shots.

Peter K

[Michael Graves]

On the two filters I use most, I simply did a film speed test using the filters. Now I have an ISO rating for film based on no filter, one with the yellow and one with the orange. I plan to do the same with my green and red when time avails. I just don't do mental math well, so this works best for me. And as it turns out, the factors aren't even numbers anyway.

[Ash]

Michael, how did you do your own film speed test?

[steve simmons]

Filter factors vary according to the color of the source light and the color of the object reflecting light back to the camera. Early and late light is warmer than mid-day light and will affect how the object reflects light back to the film. I discourage arbitrary filter factors or even testing for a factor .

Meter through the filter as I have recommended many times, as Gordon Hutchings recommends, etc., etc. Then apply an additional factor depending on which filter you are using.


steve simmons

[kev curry]

Carrying on from what Steve Simmons said.....

Gordon Hutchings recommends adding these filter factors after metering through the filter....

(*8 med yellow - no increase ) (*11 yellow green + one stop) (*12 dark yellow - no increase) (*16 med orange + one stop) (*21 light red + one stop) (*25 med red + two stops) (*29 deep red + two stops)

[David Schaller]

Have you tried metering through the filter? That's the most accurate way.

[Ole Tjugen]

Have you tried metering through the filter? That's the most accurate way.

That would be most accurate - if the OP was using a "standard panchromatic" film.

He isn't. He's using EFKE R25 and R50, which both have significantly reduced red sensitivity.

Depending on lighting conditions and so on and so on, a filter factor of about 2 to 2.5 seems right for this combination. I think that's what I used many years ago.

[riton mhilli]

Thank you for your answers
I read something about Gordon Hutching's idea to meter through the lens and to add an extra stop for some filters
Is this quite equal to Bruce Barnbaum's method,so to halve the ISO and to put important shadow details in zone IV .He uses highly diluted developers to produce good highlight details.Excuse me because I'm a little confused.If ihave to use a filter firstly i must use G.Hutching's method and then Barnbaums one.
Thanks Riton

[Ole Tjugen]

One "sensible approach" would be to measyre first through a cyan filter; since R50 is virtually red-blind; and add enough compensation on the meter to give the same reading with the cyan filter in place as the unadjusted meter did without a filter, set at ISO 50.

If you then measure through both the cyan and the other filter, that should give you the correct correction for that film under those lighting conditions.

That's an expansion of Gordon Hutchin's method, as it applies to that specific film.

Bruce Barnbaum's method I don't know, but I would assume it does something of the same in a different way?

So pick one method, and only one, or you will be overcompensating.