Rom | Tapas in the sun1d ago

I need help to work out the aperture settings for a vintage lens, believed to be approx 1915. The lens is marked:

H Duplouich, Paris, Rectilicne Extra Rapid

That is all: no max aperture and no focal length (my guess for the latter is 100mm).

The aperture scale runs from 2 to 22 with equidistant segments. 2 is the smallest aperture, 22 is WIDE OPEN, so it is not related to an f-stop scale. I think it is the aperture diameter in mm.

An idea how to work out f-stops?

#vintagelens #vintagecamera

Show threadCoprolite9000 - Pixelfed
It's been ages since I did any optics stuff back at university, but it should be as simple as N = f/D, with f being the focal length and D being the entrance pupil diameter. So the lens goes from N = 100/2, i.e. f/50 through to N = 100/22, i.e. f/4.545... (I think, anyway...)

(Light transmission etc. is probably way worse than a modern lens with anti-reflective coatings and suchlike!)

Anyway - fun thing! Looking forwards to seeing what you do with it.
Apr 5 at 10:33pmWeb
Show threadRom | Tapas in the sun1d ago

@coprolite9000 Thank you for the info. It is much appreciated!

I will try to confirm the focal length and the aperture diameter numbers as best I can. Then do the maths and carry out film testing. I will post the results here, possibly even do a blog post. But it may take a while…

I hope to use glass plates and film with this camera, once I have worked out the aperture settings and got everything working.