Ross APO Process Xpres f:10/241mm

[Bill_1856]

My "new" Gandolfi came with the above lens #72020. The aperture scale is in F stops (10-90) and mm, but there is a second independent ring in front of it which goes from 0-90 (in sequence of 5 unnamed units) in about 90 degrees of rotation.
I don't have a clue what this is/does? Can anybody help?

[Struan Gray]

In colour halftoning you sometimes use non-circular dots. You create them by putting the correctly-shaped Waterhouse stop into the process lens. The halftone screen then projects a tiny image of the stop onto the plate/film. For best results the four process colours are screened with the shape oriented at different angles.

Short form: your ring would have rotated a non-circular Waterhouse stop to predefined angles.

[Bill_1856]

Thanks. A small slot does open when the ring is rotated.
Wilhelm

[Bill_1856]

The following is the seller's description of the Ross lens which came with a camera I just bought:
"The lens shown was on the camera when I got it and is included for free - not much of a lens." It was also described as "uncoated."
I took if off the Gandolfi, carefully cleaned it, and mounted it on my Technika. It actually was coated, indicating that it is at least post-WW2.
The images produced, even wide open, are incredibly sharp as a razor, and VERY contrasty! I pointed it so the sun was directly on the front element, and could not elicit any flare.
I think he was misdirected by the incredibly dim ground glass -- (Gawd only knows how old the camera is) -- it badly needs a new GG and Fresnel.
It turns out that this "not much of a lens" was among the best I've ever used. The only problem is that it's barrel mounted.