Lever Stops on Darlot Hemisperique

[peterkinchington]

I have just bought an old vintage brass lens that I intend to use for landscape photography on my 8x10in camera. It is the Darlot Hemispherique 130mm built for Marion & Cie. I believe it is a homocentric design. My question is it has three lever stops marked 3, 5 and 7. Are these actual diameters in mm (3 is the smallest opening) or are they an unusual aperture scale?

[retrofocus]

It has been suggested in the old threads that according to book "Atelier und Apparat des Photographen" by Otto Buehler, from 1869, Weimar indicates the #'s represent the # of times the exposure must be increased from full aperture. i.e. 3x, 5x, and 7x for the smallest aperture.

So when you have three levers, you have four different apertures: no lever is equivalent to "full open". Widest aperture seems to be mentioned depending on the source as F/12 - F/22. I'll measure when my lens arrives. Aperture is perfectly round as opposite to iris based apertures with shape depending on the number of blades.

[Greg]

I have found rotating aperture stops on vintage brass lenses to be very inconsistent.
My Gundlache Wide Angle - 1, 2, 3, 4, 5, 6
My Extreme WA Periscope - 10, 14, 20, 28, 40, 56
one generic one was even labeled - 2, 4, 8, 16, 32 and it's stops were in a progression of one f/stop

[peterkinchington]

It has been suggested in the old threads that according to book "Atelier und Apparat des Photographen" by Otto Buehler, from 1869, Weimar indicates the #'s represent the # of times the exposure must be increased from full aperture. i.e. 3x, 5x, and 7x for the smallest aperture.

So when you have three levers, you have four different apertures: no lever is equivalent to "full open". Widest aperture seems to be mentioned depending on the source as F/12 - F/22. I'll measure when my lens arrives. Aperture is perfectly round as opposite to iris based apertures with shape depending on the number of blades.

Thanks for the info. I'll use this info. to start determining what exposure times work for me.
Cheers Kanga

[peterkinchington]

I have found rotating aperture stops on vintage brass lenses to be very inconsistent.
My Gundlache Wide Angle - 1, 2, 3, 4, 5, 6
My Extreme WA Periscope - 10, 14, 20, 28, 40, 56
one generic one was even labeled - 2, 4, 8, 16, 32 and it's stops were in a progression of one f/stop

Hi Greg, guess I'll have to determine the exposures through trial and error.
Cheers Kanga

[retrofocus]

I have found rotating aperture stops on vintage brass lenses to be very inconsistent.
My Gundlache Wide Angle - 1, 2, 3, 4, 5, 6
My Extreme WA Periscope - 10, 14, 20, 28, 40, 56
one generic one was even labeled - 2, 4, 8, 16, 32 and it's stops were in a progression of one f/stop

You may know this already, but there is the handy conversion table: