Originally posted by vonBaloney They have them at Adorama, etc also. Anyway, they are just fancy washers that happen to be exactly the right size -- I think they are rubber over metal as they snap in with magnets on a Lensbaby. Mount the lens on the adapter -- stick the disk in from the other side as far as it will go and it will stay snugly with a friction fit. The thing that they come in has a plastic hook or magnet to get it out again.
Remember to have them as close to the lens as possible as vignetting will progressively increase as the distance increases.
It will be interesting to see what aperture they come out at.
I doubt whether the lensbaby f rating will be correct-- if so it will be a coincidence.
I approximate my rings at f4.5 and they are about 6mm and almost on the glass.
The formula for aperture (focal length / iris diameter ) won't work here as the washers are not at the optical centre of the lens.
It seems to be f4.5 for all 3 lens - I guess they designed the lens as such coz it would make sense at the camera body end. (for metering).
If I have thought this through right the effective aperture will change if you don't consistently push the washer to the same spot.
Last edited by GUB; 04-16-2014 at 03:20 PM.