Seele,
I don't have the elmar, but I do have the Industar-50, a Russian copy, and have used it on the Bessa R, BUT I DID NOT, REPEAT NOT, COLLAPSE IT INTO THE BESSA. I cannot say if the elmar would do the same, but the I-50 reaches deep enough to cause damage to the shutter. If you don't push it all the way it, you might be able to use it. I just screwed mine on and took a pictuer and then removed it. Works that way! Some of the Leicaphilles might be able to answer this directly.