Antique Lens Question

[MikeK]

I have a Scovill Waterbury Lens - It came to me in three pieces. The lens barrel, the lens and mounting ring and the washer type f-stop. The lens is a very simple one element. One side is convex the othe is flat. I get an image no matter what side faces the film but anyone know for sure which side should face the film?

The lens had some fungus but a soak in bleach and rinse/dry and then finshed with a lens cleaner and quick polish with a lens cloth and it looks like new

Mike

 

[jimgalli]

Hi Mike. I just tested one of those in the last month. I wrote a little piece and it's (there was a url link here which no longer exists). The empty barrel should face out but it's so simple I doubt it would make any difference.

 

[MichaelBriggs]

If I understand the type of lens from Mike's description, then the orientation makes a big difference. Despite the apparent simplicity of curved achromats, their optics aren't trivial. Kingslake qualitatively explains their performance in the second chapter of his book "A History of the Photographic Lens".

Daguerre asked Chevalier for help for a camera lens. Chevalier experimented with telescope objectives and noticed that the image was poor for both orientation of the objective, but in different ways. With the flat side of the lens facing the image, there is severe image curvature. With the flat side of the lens facing the subject, the image is flat but has severe coma. The coma can be controlled by placing a stop in front of the lens. Since the flaw of the flat-facing-the-subject orientation (i.e., coma) can be controlled with a stop, this is the better orientation. A google search found drawings that showed a stop at the front of a Scovill Waterbury Lens, so this may be the design of Mike's lens.

If it seems like the lens is designed to have the stop behind the lens, then perhaps it is a later design. You might want to study some of the pictures in this chapter to guess which type of lens you have.