Hi,
Does anyone know about this lens . It's engraved with Rath. Opt. Tnd? Anst? vom? Emil Busch Rathenon. I think that's what it says, the way it's engraved I can not decipher an "R" from an "N" or something else.
I only ask because I'm using it on a 5x7 camera and I have been stopping way down to make counting easier. I have since bought a lot of ND, but the weather is rubbish I can't use it.
My question is because it says "Portrait" can I expect a soft focus at wider Apertures, the fact that it goes to f4 makes me think it would. At f64 and smaller it's pin sharp. Also any idea of it's focal length, I'm guessing at about 150mm - 160mm.
Any information practical or historical is most welcome.
Being brought up on modern shuttered lenses these brass barrel lenses are a mystery to me.

Thanks

Kevin.