Speed of half the Eidoscope

[Marko Trebusak]

Hi,

Since I moved to 5x12 format, I need to put aside Eidoscope #3, as it would not cover, except in macro conditions. Since Jim Fitzgerald is using the rear element only with great success, I would like to try that myself as well. Is this objective trully simmetrical? I'm trying to determine the position of f-stops for rear element only, and if objective is simetrical indeed, then it is safe to guess, that F5,6 of a whole objective means F11 for just the rear cell. Or is my logic a bit off?

Cheers,
Marko

[Dan Fromm]

I just looked at an Eidoscope cross-section in a 1950 Berthiot catalog. It certainly looks symmetrical.

[Jim Fitzgerald]

I know that my half of a 150 Eidoscope that I have I figure at about 275mm or 280 mm and around F8-11. Now mine is in a shutter thanks to Jim Galli so I've got the stops up front. I love this lens! If I could only take one lens out with the 8x10 it would be this one. Find the right scene and this baby shines!