Petzval with aperture marked 1 - 5.

[pjd]

Does anyone have any ideas about the likely origins of this unbranded Petzval? Or the aperture markings, they don't refer to any scale I'm aware of. Back focus is about 18cm, roughly a 3.5cm aperture wide open. I don't have the lens to get better photos, no markings on the barrel other than the 1 - 5.

[pjd]

I've had a couple of messages about this through email; to be a bit more clear - I wonder if anyone has a guess of country of manufacture (I think not continental Europe, for example - but I don't know much about brass lenses), and if anyone has a lens with similar set of numbers (1 - 5) for aperture. The 1 - 5 doesn't match up with the US system or the Dallmeyer system.

[Hugo Zhang]

I have a Voigtlander Euryscop iii #6 lens with an aperture marked 1-5. Since I know that max (1) aperture is F4.5 and I just assume 2 would be one stop smaller.

[pjd]

I have a Voigtlander Euryscop iii #6 lens with an aperture marked 1-5. Since I know that max (1) aperture is F4.5 and I just assume 2 would be one stop smaller.

Thank you for the information, that's surprising (and interesting). Do you happen to know the age of that lens, roughly?

[Vaidotas]

I have the same looking petzval which I aquired out of curiosity.
I thought maybe there is some markings on the lens elements but my example back element thread corroded with the same white residue.
What I found interesting - front achromat has longer FL in comparison to other 5 cm lens diameter examples I have.

[Jim Jones]

I've seen old lens apertures marked in numbers that have no logical relation to typical f/numbers. The f/number is the apparent diameter of the aperture viewed through the front lens elements divided into the focal length of the lens. That focal length may differ from the distance from lens to image, especially in telephoto and some wide angle lenses.

[Hugo Zhang]

My lens serial number is 31706 which dates the start of its life in the year of 1886. The aperture markings are 0-5 instead of 1-5.

[Steven Tribe]

The reason for these illogical markings (same distance between numerals) aperture scales on Petzvals is because:—-

- they were not used for taking photographs!

They were used on mostly horizontal enlargers where there is usually a trial and error illumination of test papers. The numbers are just a reference in getting a repeatable aperture - which gave the best result on test papers.
A lot of these Petzvals with lever iris apertures have no F indications - were also used in enlargers and the other devices around the turn of the century.
I enclose a photo of one without either makers name or iris position marks. Note the extremely long protuberence - useful in a darkroom!
The “no name” state is perhaps best explained by enlargers being well plastered with name plates , like magic lanterns.

[Tin Can]

Very interesting!

Thank you

The reason for these illogical markings (same distance between numerals) aperture scales on Petzvals is because:—-

- they were not used for taking photographs!

They were used on mostly horizontal enlargers where there is usually a trial and error illumination of test papers. The numbers are just a reference in getting a repeatable aperture - which gave the best result on test papers.
A lot of these Petzvals with lever iris apertures have no F indications - were also used in enlargers and the other devices around the turn of the century.

[pjd]

Thank you to all who responded, interesting. I'd not thought about use as enlarging lenses.