Flange focal length calculation

[Thierry Schreiner]

Hi,

First of all, a Happy New Year to all of you LF guys out there.


My question is basically very simple, but as so often, I don't know the answer.


How do I calculate the flange focal length of a lens for a given distance?

Example: At infinity, the G-Claron 355mm f9 has a Flange Focal Distance (distance from back of the shutter to film plane) of 350mm.

Is there a formula to calculate the FFD for the lens if focusing distance is set at 10 metres, 5 metres, etc.


Thank you in advance for your answers.

Best regards from France

Thierry

[Dan Fromm]

http://www.glenbrook.k12.il.us/gbssci/phys/Class/refrn/u14l5f.html

http://hyperphysics.phy-astr.gsu.edu/Hbase/geoopt/lenseq.html

Two presentations of the same ideas.

[Thierry Schreiner]

Dan,

Great. A 1000 thanks. This really helps me.


Best regards from the old continent.

Thierry