View Full Version : Seneca Rapid Rectilinear lens

David Van Gosen
23-Mar-2005, 15:48
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
23-Mar-2005, 16:25
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
23-Mar-2005, 18:06

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 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
24-Mar-2005, 09:10
Thanks for the help. We'll see how it works out in a week or two.