Adding Filter Factors- B&W

If I'm using a filter, I shoot my spot meter through the filter.

The best way to determine filter factors is to actually photograph a gray card or even better a color chart like the Jobo with the filter. Different films have different spectral responses and if you have a film you use constantly this is the best way to determine the filter factor.

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The best way to determine filter factors is to actually photograph a gray card or even better a color chart like the Jobo with the filter. Different films have different spectral responses and if you have a film you use constantly this is the best way to determine the filter factor.

won't do this

The other 'factor' no one has mentioned is the reflective value and color of the subject and that of the filter,i.e. that a subject reflecting red light will get more light through a red filter than a subject reflecting blue light. This is why Hutchings recommends metering through the filter and not just applying an arbitrary factor.


Meter through the filter each time (this will take into account the color of the light - mid-day blue or early/late warmer light) and follow Hutchings' instructions. It is so simple and so accurate.

steve simmons

I agree that it could be the difference between the hand held and TLR meters. I'd try pointing them both at an 18% grey card and see what you get. The 35 mm is also probably an averaging meter, so it will work for average scenes. On the other hand if you aren't assesing what zone to place your spot meter readings on, that would put it off as well. Another variable is the shutter in the LF lens compared to the shutter in the 35 mm.

How about using just the spot meter, and exposing both the LF and 35mm by it's readings, and then comparing?

You probably should do Zone I ISO / EI tests with the LF setup anyway.

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Originally Posted by steve simmons

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The best way to determine filter factors is to actually photograph a gray card or even better a color chart like the Jobo with the filter. Different films have different spectral responses and if you have a film you use constantly this is the best way to determine the filter factor.

won't do this

The other 'factor' no one has mentioned is the reflective value and color of the subject and that of the filter,i.e. that a subject reflecting red light will get more light through a red filter than a subject reflecting blue light. This is why Hutchings recommends metering through the filter and not just applying an arbitrary factor.


Meter through the filter each time (this will take into account the color of the light - mid-day blue or early/late warmer light) and follow Hutchings' instructions. It is so simple and so accurate.

steve simmons

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Steve, Steve.... You are wrong, the purpose of using a gray card is to see how much light the filter absorbs WITHOUT the interference of color, that is the purpose of filter factors. It is really not important to know how much more light of the same color the filter lets through.

In fact, if you meter through a red filter on a red subject you will get a gross under exposure using your method. The important thing is to see how your FILM reacts to the filter, NOT your meter... :rolleyes: