Interesting... i have recently trying to clean foggy/oily back element of some Sigma 18-35 (not 1.8 but 3-4.5 or something) and i could not reach it from behind, so i tried removing front elements, focus group and so on, in attempt to reach problem on rear elements group... and still failed... its all welded plastic and glue... anyway, during battle with helicoid (for focus group) i tried on the lens, on camera, with no front group and i was able to reach super close, almost to contact with subject and be able to get decent focus, even to control the aperture...i expect even af would work if focus group was bolted in... i will most definitely try this as well... i had some similar experiments with some projector and xray lenses, but never gave it much thought for some real use because there was no some (reliable and safe) mounting options... thanks for nice video!
Interesting... i have recently trying to clean foggy/oily back element of some Sigma 18-35 (not 1.8 but 3-4.5 or something) and i could not reach it from behind, so i tried removing front elements, focus group and so on, in attempt to reach problem on rear elements group... and still failed... its all welded plastic and glue... anyway, during battle with helicoid (for focus group) i tried on the lens, on camera, with no front group and i was able to reach super close, almost to contact with subject and be able to get decent focus, even to control the aperture...i expect even af would work if focus group was bolted in... i will most definitely try this as well... i had some similar experiments with some projector and xray lenses, but never gave it much thought for some real use because there was no some (reliable and safe) mounting options... thanks for nice video!
I think that's probably why we can do reversed mounting ring to achieve macro.
'promosm'