Wollensak 6 1/4" infinity focus

[joedgaia]

I have a Wollensak 6 1/4" lens on an 8x10 camera and according to what I have read the lens should focus at infinity approx 6 1/4" from the ground glass. I am trying to accurately calculate bellows factor and the infinity focus on this lens is about 5 1/4" from the ground glass. I surmise I should use this distance for base exposure and calculate the bellows factor from there?

Thanks, J

joe murray | nativesonsfilms.com
Directors Guild Of America-Director
Int'l Cinematographers Guild -Director of Photography

[Mark Woods]

Depending on the lens design, your 5 1/4" could be accurate. And, like you said, I'd base my bellows factor on the 5 1/4" base.

Enjoy your shooting.

Mark

[Mark Sawyer]

When in doubt, just figure your f/stop from scratch. It's just a ratio. But I can't imagine why you'd use that lens to shoot close enough to require bellows extension factoring...

[mdarnton]

Probably not the case, but it needs to be asked: are you measuring from the center of the lens, where you should be, or from the irrelevant back of the lens?

[joedgaia]

I'm measuring from the optical center. When doing a foot to toe portrait there is about 7-7.5 inches of bellows ext and that would require about 1 stop of exposure compensation.