I recently purchased an Ebony 23S, which is a wonderful camera. I also bought a Horseman monocular reflex viewer, adapted by Ebony to work with their hinged GG and fresnel. The lenses I am using are a Rodenstock AR-S 135mm (ƒ5.6) and a Schneider SA 65mm (ƒ5.6).

The problem is the degree of light falloff in the viewer. It is extreme! With the 135mm lens under brilliant light it is workable but far from satisfactory. With the 65mm lens it is not usable.

I know I can get an Ebony WA fresnel that would help with the 65mm. And Andrew Ito recommended Bill Maxwell focusing screens.

Does anyone have a solution specific to a viewer like this, particularly one that would work well with either lens (this is a field camera and I am trying to keep my kit weight and bulk to a minimum)? I occurs to me that a second lens, on the viewer side of the GG, to bend the light to the objective might be what is needed.