Mystery brass lens

[Kami-the-Trout]

Trying to figure out more about this lens . . .

(Link to Flickr pic) http://www.flickr.com/photos/7898516@N08/4386174400/

Focal length is 14 inches at infinity.

It has waterhouse stops. Wide open (no stops) is f/5.6 ish. Smallest stop is about f/28. Wide open it is quite soft and dreamy, sharpens up a lot by stopping down.

There is a front element, that when in place extends the focal length to about 28 inches.

It's possible to shoot without the front element as well. It seems to add no quality, it just extends the focal length.

There are absolutely no markings on the barrel.

It easily covers my 12x15 inche plate camera at infinity, with movement to spare.

Any one have thoughts on origin/history/time period?

 

[goamules]

It's probably a rapid rectilinear / aplanat from around the 1890s. You can research counting the reflections in the glass, but basically they are two cemented doublets on each end.

Garrett

 

[panchro-press]

I'm confused.
You state the focal length is 14" at infinity. Then you say there is a front element which extends the focal length to 28".
Is this an additional front element which goes in front of the front element when the lens is at 14"?

David

 

[Kami-the-Trout]

I'm confused.
You state the focal length is 14" at infinity. Then you say there is a front element which extends the focal length to 28".
Is this an additional front element which goes in front of the front element when the lens is at 14"?

David

That's the odd thing about the lens. The front element screws out, almost like it's a filter instead of a required element. The pics look fine without it. If I take it out (and I mostly use it without), there is no element in the front at all. The only element then is the rear element, behind the waterhouse stop.

When it's screwed in, the focal length doubles. Without it, the FL is 14 inches.

I counted reflections as suggested above. There are three reflections in the rear element and two in the front screw-in element.

 

[panchro-press]

Have you ever tried the front element on the rear, with the rear element removed?

David

 

[Kami-the-Trout]

Have you ever tried the front element on the rear, with the rear element removed?

David

I hadn't tried that, but just did.

The front element moved to the rear by itself will not form an image.

 

[removed account4]

im with garrett ...