How do I use a non-TTL light meter with ISO 800 film and extension tubes?

Question

I’m using a Zenit 11 with its built-in non-TTL light meter. The meter’s ISO/ASA dial only goes up to 500, but I’d like to use faster film such as ISO 800. If I meter at ISO 400 instead, how should I adjust the exposure settings the meter suggests?

I also want to use extension tubes (9mm, 16mm, 30mm) with a 58mm f/2 lens for close-up work. Since the meter does not measure through the lens, it won’t account for the light loss from the tubes. Is there a practical way to compensate for that, such as adjusting the ISO setting or calculating an exposure correction?

user72258 · Answer

Yes, you can definitely use set the light meter at 400 and figure out what the exposure has to be at 800. It's a one stop difference so if it's saying f/5.6, set your aperture to f/8. Most old lenses will have the markings at one stop intervals. And it's a good idea to memorize the major f stops as well.

With extension tubes, there's usually a compensation value associated with them. Otherwise, I would do a few experiments on non-critical items. Meter the subject, shoot as the meter says, expose one stop higher, expose two stops higher, etc. Then label the tubes accordingly. Expect one to two stops of required added exposure for extension tubes.

Have fun!

How do I use a non-TTL light meter with ISO 800 film and extension tubes?

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