View Full Version : Convertible lens usage

anthony marsh
11-Feb-2014, 13:06
I have a SEROCO 5x7 glass plate with a convertible lens. There is only the front element on the shutter. Can it be used for landscapes with just the front element? Also does anyone know where to locate septums to enable the use of sheet film?

11-Feb-2014, 13:19
Can you focus the lens? Does it give an image on the GG?
If so, it can be used, for landscapes or anything else you wish.

anthony marsh
11-Feb-2014, 13:23
Ari,Thank you for the fast reply.

11-Feb-2014, 13:33
Hi Anthony; I wasn't sure what you meant by the lens being suitable for landscapes (wide angle?), but I can tell you that a convertible lens is meant to be used with one or both elements, and in various configurations.
Make sure when you deviate from the standard arrangement, that you know how that affects your f-stop scale.
For example, with both elements in place, you might have f6.3 maximum aperture; with the front element only, it may go down to f9 or f11, for example.
Good luck, and post your results.

Steven Tribe
11-Feb-2014, 14:30
Film "septums" are usually called film sheaths and are available on the FS section or eb*y.

Availability has definitely been declining, recently. Most have good markings on the reverse side - those from Kodak have clear indications of size.

Robert Opheim
11-Feb-2014, 14:53
I have a convertible lens a symmar 180 / 315mm. The rear element will work as a separate lens - however it is a very soft lens stopped down. I think that there are very good convertible lenses such as protars. I have never used these lens - there are members here that can advise you on them. As far as your lens what lens is it? You will need to determine if it was designed to be used as a front element, rear element, combined element lens. There is a lot of information on many lenses at Camera eccentrics info.

Jim Noel
11-Feb-2014, 16:06
I use convertible lenses rather frequently. Protars are my favorite, as they are for many others.
I have and use Rapid Recilinears, early PLasmats, etc. For most, when a single element is used it si moved to the rear.
This morning I made 2 images with a Chevalier designed and made n 1839-40. Amazing sharpness wide open.
No I won't post an image. I don't believe in giving my images away to the Chinese or other internet lurkers.

11-Feb-2014, 18:49
Also be aware that much more bellows extension is required when using only one cell.

17-Feb-2014, 09:35
hi Robert. I also had the 180/315 symmar and got rid of it because it was too soft without the front group. I had hoped that at 315mm it would have been good for portraits, but the softness wasn't what I'd call pleasing. On the other hand, I have a Turner-Reich 12-19-25" convertible that I'm quite pleased with. I've not used the front element on its own yet (25") because I don't have enough bellows, but the back group on its own (19") produces nice results. With all elements in place it's a 12", and the results thus far have been good. I've been using it with a yellow filter on the back group (series VII; the usual retaining ring threads on fine).