Help identifying mystery lens

[OeT]

Hi just bought myself a help mystery lens and wonder if anyone here might recognize it and can give some info about it.
Outside diameter is about 54mm and the leangth 60mm.
No aperture or slot for aperture plates and no markings of any kind.
It came with a 110mm brass tube with a slot for aperture plates but dosn't fit the lens.

[IanG]

It's a projection Petzval, cheap and very cheerful. Made by various companies, optically what ever you can eek out of it, usually for lantern slides but less coverage at infinity.

Ian

[OeT]

Thanks just checked it by holding it against my camera and it looks like it almost cover 4x5, a little to dark to tell at this time but it seems a bit dark in the corners.
I will make a lens board for it tomorrow and check more properly.

[OeT]

I made myself a lens cap and lens board.
Could I add a waterhouse stop infront of or behind the lens or does it have to be inside the lens?

[Steven Tribe]

Card cut-outs in front of the lens are fine. Early Petzvals used this system. You may find there is a removable restricting baffle inside the barrel.

[Greg]

Card cut-outs in front of the lens are fine. Early Petzvals used this system. You may find there is a removable restricting baffle inside the barrel.

Anyone know why the waterhouse stops were changed from being in front of the lens to being inside the lens?

[Two23]

I think the earliest stops were actually "washer" stops. Waterhouse was the name of the guy who came along later in the late 1850s with the slot for internal stops. My guess as to why better inside is the beam of light narrows like this: >< in the middle of the tube. Maybe the aperture has more effect at that point (nodal point?) I have an 1858 Derogy Petzval that uses internal washer stops and an 1854 E. Woods pillbox that uses external washer stops. My 1862 Voigtlander Petval has a factory slot.


Kent in SD

[Steven Tribe]

Here is well illustrated summary of the historical development of stops!

http://earlyphotography.co.uk/site/lens_diaphragm.html

As it is a UK site, it doesn't mention the French use of mid barrel insert of washers (and supplementary lenses)! French makers developed the split barrel (fine screw thread or bayonnet) to make conversion of Petzvals to a longer focus Landscape lens. This must have given an Eureka moment to someone who realised the divided barrel could incorporate a stop system!

I too have a pre-whs Derogy Petzval. But in my example the join in the barrel as been carefully filed to allow WHS insertion.
This has been done on the achromat side so the stops can be employed on both the portrait and landscape use.

[OeT]

I'm trying to figure out the F-stop of the lens.
It's focal length are about 70mm and the lens diameter 37mm which should give a F-stop of around 1.8 could this be correct?
I thought it would be much slower.