View Full Version : Zeiss 3.5 Tessar

8-Jul-2012, 14:04
Mounted in a Sekio LS22 is a Carl Zeiss 3.5 100mm. s/n 4153922, the lens appears to be coated with very light scratches in the front element. The problem is that the sekio goes from F-8 to 64, but if you go past the f8 it will fully open to f3.5, just no numbers for reference. Would this mean that the shutter was made for a f8 lens? Kinda confused on how to handle this. The shutter works perfectly from 1 to 500 sec and has good X sync.

Dan Fromm
8-Jul-2012, 15:16
The shutter's aperture scale is for a lens with maximum aperture of f/8.

You don't know the maximum aperture it gives with a 100/3.5 Tessar fitted. f/3.5 is possible, but smaller is possible.

To estimate, hold the lens (in shutter) at arms length with the shutter's diaphragm wide open and the front of the lens facing you. Measure the diameter of the entrance pupil. That diameter/100 is the f/stop with the shutter's diaphragm wide open.

If you want to use the lens in that shutter, have a new aperture scale made to suit the lens. www.skgrimes.com can do the job

Jim Jones
8-Jul-2012, 19:09
Dan is right, but you can also use the scale as is, and allow for any difference between actual and indicated aperture. I've calculated scales as Dan suggests and inked them onto white tape covering an original scale.