Seneca Rapid Rectilinear lens

[David Van Gosen]

I just won a Seneca Rapid Rectilinear lens off our favorite auction site. It's listed as an f/8, with focal length around seven inches. I'm going to assume that f/8 here isn't the same as f/8 in the modern system. Does anyone know which older system was used? I know I've seen tables for converting to modern f-stops. Also, has anyone used the Seneca lenses? I've read that the Rapid Rectilinear design was good, and that Edward Weston used one, but I haven't seen any info about Seneca in particular.

Thanks, David

[Jim Galli]

Actually I think it probably is our modern system. Run of the mill RR's were typically f8 lenses. Many are convertibles too. Some are un-symmetrical and give you a triple convertible. On the old US system a normal RR would be f4 - f256. I have an old Wolly Rapid from the 1920's that can deliver a grand image at f64. The key is to just use the sweet spot out of the middle. Mine is a 13" and I use it on 5X7 so it's not out in the softer edges.

[Bob Fowler]

David,

Most likely, the lens will be marked in US. US stands for Uniform System, not United States. The US stops are different from modern f/stops, here's a conversion list

(US/stop:f/stop)

US 1 = f/4

US 2 = f/5.6

US 4 = f/8

US 8 = f/11

US 16 = f/16

US 32 = f/22

US 64 =- f/32

US 128 = f/45

US 256 = f/64

I have a superb B&L RR on my Century 4a studio camera. It's not marked for focal length, but my best guess - not having measured it - is that it's a 10" lens. It's a US 4 lens, so it's a tad slow by modern standards. I also have a Wollensak Triple that's marked in the US system.

The lens collector's vade mecum doesn't have a lot of info on Seneca lenses. The only mention of the Seneca RR indicates "about 1906" and that Rapid Rectilinear lenses were made in focal lengths from 5.0 to 18.5in.

[David Van Gosen]

Thanks for the help. We'll see how it works out in a week or two.