480mm Apo Ronar

[Mark Sawyer]

I come before the group pleading ignorance... I just bought a 480mm Apo Ronar, and there's a little widget sticking out a slot on the side of the barrel just in front of the aperture scale. It moves smoothly about 120 degrees around the barrel, but has no markings and doesn't seem to move anything inside the lens. Anyone know what that little guy is there for?

[Bob Salomon]

It is the filter slot control. You boulght a lens from a process camera. This slot was not on the versions in shutter for view cameras.

[dave bulmer]

Hi there Mark. I had a 480mm Nikkor process lens that had a similar slot for filters. It didn't make any difference to the image when used as a view camera lens.

Dave

[Ernest Purdum]

Keep it closed, though.

[Øyvind Dahle]

If you have filterholders that fit, you can cut polyester or gel-filter to put inside. As a result, the filters for this lens are the smallest, mine also fit a 360mm Apo-gerogon.

Or you can put in something black to avoid any light coming in.

Øyvind

[Mark Sawyer]

Thanks, all! I was sliding the little widget around while looking into the lens and couldn't see it do anything inside. Now I see it closes the filter slot. Duh...

[Struan Gray]

I'm pretty certain the slot is not for filters, but for Waterhouse stops. When screening images for printing on a press the dots on the screened version are tiny replicas of the shape of the stop. For some applications, particularly colour seperations, different shapes would be used for different inks, or a non-circular stop would be rotated to different angles. Some process lenses have an angular scale along the edge of the slot so you can rotate the stop by defined amounts.