View Full Version : Flange focal distance

Jim Jasutis
6-Mar-2001, 19:23
There seems to be more to choosing a lense for a large format camera than there is in 35mm. I have come across the term "flange focal distace" in some of the le nse specification literature. What does this term refer to, and how does it rela te to belows extention? Thanks


Louis Jensen
6-Mar-2001, 20:12
Flange focal length is the bellows extension when focused on infinity.

Kevin Crisp
6-Mar-2001, 20:49
I always thought the phrase meant the distance from the film to the lens when focused at infinity, with the measurement on the lens being taken off the flange which holds it to the lens board. This would be (within a couple mm) the same as measuring from the lens boards.

Jim Jasutis
6-Mar-2001, 21:23
Thank you for your responses. They confirm what I had thought to be the answer. What prompted my question was some information I got from the Schneider lense site. The specification for the super-symmar XL 5.6/110mm listed a flange focal distance of 157.9mm. This sounded out of line with the answers you gave. Since then I have found another site where the flange focal distance is listed as 117.2mm. This sounds more like what I would have expected. I'm guessing the first number could have been a misprint. Thanks again. JimJ

neil poulsen
6-Mar-2001, 22:30
It appears that the schematics for the 110mm and 150mm Super Symmar XL lenses have been swapped. In addition to having a larger flange focal length, the 110mm also "appears" to be longer and wider. I sent them a note. I wonder if they'll be grateful enough to send me one of these two lenses. I'll have to ask.