Wollensak Vesta 11.5" / 17"

[DrTang]

okay braintrust


when one flips that back section to the front creating a 17" lens.. does the effective aperture change from f5 ?


I imagine it would, yet there are not markings for it on the studio shutter it is in

[Louis Pacilla]

I'm pretty sure It's about double the combined lens speed, so around f10 Maybe a hair less like a 1/3 of a stop.

[DrTang]

thanks

at least that is somewhere to start

[goamules]

okay braintrust


when one flips that back section to the front creating a 17" lens.. does the effective aperture change from f5 ?


I imagine it would, yet there are not markings for it on the studio shutter it is in

Actually, you convert them by flipping the front (cemented double) to the rear, behind the aperture. You meant that I'm sure.

[E. von Hoegh]

FWIW http://www.cameraeccentric.com/html/info/wollensak_13.html

Vesta is on pp.24

[DrTang]

FWIW http://www.cameraeccentric.com/html/info/wollensak_13.html

Vesta is on pp.24

Thanks..yeah..I had found that. and that told me how to swap the front element to the rear for the 17"... but it doesn't mention how fast the lens would then be

[davehyams]

The vesta is f/5 normally no? so that would give you a diameter of 2.3 inches max, so when shot with the cemented doublet keeping the same 2.3 inch max aperture would give you a speed of f/7.39. Might want to check the math on these as I dont have the hardware in front of me, but I think thats right.

[goamules]

Approximately F8, but it may be slower due to the iris fixture. Like Dave says, Wollensak called them F5, so that supposes a 2.2" apparent aperture (11 divided by 2.2 = 5). So if it changes to a 17", it would be 17 divided by 2.2. You can verify this by measuring the opening when you have the lens.