Please urgent:Rodagon Rodenstock f2.8 or f4

Hi my friends!
I need an advice,it's very urgent.
I'm going to do lith sessions in the darkroom.
I'll work with diaphragms as f4,f5.6.
So working with these diaphragms...which lens should be better?...Rodenstock F2.8 or Rodenstock F4?
Please help me!

Adiós

There will be very little difference.

Assuming you are speaking of a 50mm lens, the f/2.8 version is probably a slightly better lens over-all.

What Matt said...

What Vaughn said Matt said...

The lastest-version 50mm f/2.8 and f/4 Rodagons are identical optical designs. The aperture limitation in the f/4 is only there because the blades are set to stop at that point. Likely Rodenstock wanted to make an alternative to the f/2.8 against as little cost as possible.

The above concerns the latest version, the one where you can make the aperture continuous by sliding a small, raised lever on the side of the lens. I don't know about earlier versions (the one with the red line and rubberized aperture ring, and the even older version with the silver-black, bit-like pattern on the nose).