Effective aperture with 55 f/2.8 Micro-Nikkor on copal 0

[noogie]

HI!

I've managed to mount my broken (stiff and oil on blades)
55mm f/2.8 Micro-Nikkor on a copal 0 shutter,
and I've got great magnification, but when I wanted to take a shot, I realized I have no idea what the aperture really is

is it still 2.8? or has it changed because of the shutter small hole?
if so, what is the effective aperture of this setup?

[Peter K]

You can measure the aperture as with any other lens too described by Emmanuel here (http://www.largeformatphotography.info/forum/showthread.php?t=32332).

The Micro-Nikkor 55 has a very deep lenshood. This lenshood has to be removed to measure the aperture at the entrance pupil.

Have fun
Peter

[Dan Fromm]

f/2.8. When you front-mount a lens, its built-in diaphragm controls aperture. A wide-open #0 has a larger aperture than a wide-open 55/2.8.

Effective aperture = aperture set* (m +1). m is magnification.

m = 1 + (extension from infinity position)/(focal length).

If you're going to use a 55/2.8 MicroNikkor on a view camera, odds are that m > 1. If m > 1, the lens should be reversed.