B&W film development time and filter factor

[ymc226]

I have been getting the results I like rating B&W film at half the speed to get the skin tones I desire. (I use the in camera meter placing the skin in the area which the camera meters so in actuality, I am rating the film at box speed.) I use the developing time for half speed which is shorter.

Never used filters before but after reading the recent threads regarding more widespread use of filters, especially to accentuate the sky or foliage, I've just ordered a B&W MRC yellow/orange and yellow/green filter in 2 sizes from B&H and should be here in 6-10 weeks. I plan on taking pictures on the beach in Nantucket so there will be lots of sky and foliage which would make best use of the filters.

According to the filter specification, I need to add a stop for the yellow/green and 2 stops for the yellow/orange filters. If the film is rated at 400, do I still develop at the 400 time as a starting point or, for example, for the yellow/orange filter, overexpose 2 stops (equivalent 100 ASA) and develop less using the 100 time?

I am thinking that since there is less light of certain wavelengths reaching the film using the filter, I need to keep the development time at the 400 speed level.

Hope this question makes sense.

 

[Tim Gray]

Keep the development time the same. For example, if you normally rate the film at 400 and develop with the 400 time, then put the filter, adjust the exposure by the filter factor, but develop it at the 400 time.

As far as exposure, it depends on how you meter. If you are metering through the filter with the in camera meter, the meter will (more or less) account for filter and you don't need to adjust exposure. However, if you are using an external meter, you need to account for the filter when you transfer the meter reading to your camera.

For example, if you filter needs 1 stop of exposure adjustment and your in-camera meter says the exposure is 1/125 at f/8 WITHOUT the filter on the lens, when you put the filter on the lens and meter again, the meter will report 1/60 at f/8. Your external meter should say 1/125 at f/8. That agrees with the in-camera meter reading with no filter. If you put the filter on your lens, you should add one stop of exposure to the external meter reading, putting you at 1/60 at f/8.

Hope that wasn't too convoluted.

 

[Chris101]

If you have a ttl meter, don't change the iso to compensate for the filter - the light reaching the meter will be passing through the filter. If not, try holding the filter (or the other sized one, since you said you are getting two different sizes) in front of the meter and taking a reading that way. This is marginally better than just blindly adding a filter factor because it takes into account the color of the subject and how much of the reflected light gets through the filter.

For example, if you are shooting a forrest, more of the reflected light is green, and more of it will pass through a green filter than the filter factor will account for, as the factor applies to a neutral color.

Than don't change your development at all from how you are doing it now.