Rodenstock 240mm F/5.6 S
 

I got a Rodenstock 240mm F/5.6 S in great condition, and while mounting
it on a lensboard I became puzzled by the retaining ring and spacer. I
am not certain what the spacer is for. The front and rear elements
appear to join properly without the spacer. In fact, with the thick
board, the spacer leaves few threads to engage the nut.

I've found no manual (yet) for it.

Any clues?

Rodenstock 240mm F/5.6 S
 

"John J" wrote in message
m...
I got a Rodenstock 240mm F/5.6 S in great condition, and while mounting it
on a lensboard I became puzzled by the retaining ring and spacer. I am not
certain what the spacer is for. The front and rear elements appear to join
properly without the spacer. In fact, with the thick board, the spacer
leaves few threads to engage the nut.

I've found no manual (yet) for it.

Any clues?

Set up the camera without the spacer and see with a good loupe and with the
lens wide open if you can focus on every important point (center, left upper
corner, right upper corner, left lower corner, right lower corner, top edge,
bottom edge, left edge, right edge) of the ground glass. Ditto with the
spacer. Any difference?

You may also want to try this exposing film with the lens wide open (with
suitable shutter speed) and examining the resultant negative.