Aperture of Berthiot Pan Cinor Zoom lens

[kontrabass]

I saw some C mount Som Berthiot Pan cinor zoom lens with the "dog leg" reflex viewfinder on ebay, abour 100-200 EUR. I would like to know that is the aperture behind the mirror. Because if it is , the viewfinder will be able to keep bright view always.

[bolextech]

Usually, these Berthiot lenses use a beamsplitter prism with a small reflective portion to form the reflex image and yes the aperture is behind the beamsplitter.

Cheers,
Jean-Louis

[BK]

It just happens that I have this lens on my Bolex Reflex and I can confirm that the aperture is behind the beam splitter prism, and even though you are stopped right down to F16 you still get a bright image in your dog leg viewfinder.

Quite a nice lens, soft when at maximum aperture and very flare prone since it's old technology without modern multi coatings, try not to shoot directly into the light and use a lens hood. I have the black painted version which I prefer, it attracts less attention.

Bill