Have just received a 500 Vivitar F8 mirror lens but am not sure of metering as the exposure times seem totally wrong. Do I need to compensate to achieve correct setting if so how do I calculate?

-- David White (david.white@sic.shetland.gov.uk), September 24, 2001

Answers

With the EOS 10 you'll want to go into Aperture Priority or Manual mode (Av or M), and set the aperture to F1.0. That way, it will not attempt to shut down the aperture of the lens at all, and the exposure will be correct. If you set it to F8.0, you will be WAY (6 stops) out.

The reason for this is that mirror lenses have a fixed aperture, and don't communicate aperture information with the camera body. An EOS camera will act in one of two ways about this: Either it will display "00" as the aperture, or it will assume it's an F1.0 lens. I believe the EOS 10 does the latter, and more recent cameras do the former. However, if you make sure the camera will not attempt to stop down the lens at all (ie set it to F1.0), then it will expose correctly.

-- Isaac Sibson (isibson@hotmail.com), September 24, 2001.

Hm. Second time this question has come up lately. Canon really should address the subject of stop-down metering in their manuals. Anyway. Just to follow-up on the previous response:

http://www.grocible.com/photo/10s-instructions.html

-- NK Guy (tela@tela.bc.ca), September 25, 2001.

OK. I've moved my stop-down metering info to:

http://www.grocible.com/photo/manual-lenses.html

-- NK Guy (tela@tela.bc.ca), September 28, 2001.