Minolta 35-70 3.5 macro - back focus adjustment?

[jonar]

Hi all! Don't know the correct word for it, but in my video days we performed backfocus adjustment on many lenses when the focus wasn't consistent through the zoom range. I have the same problem with my 35-70 but have no clue on how to make adjustments. I have tried to shim the SR-EOSM adapter but it seems only to have effect on the infinity focus. Any ideas or input?

Cheers.

[philslizzy]

Focus on cine/video zoom lenses must be consistant through the range because the zoom may be used while filming. This is a parfocal lens.

On still cameras old zooms were not designed for film work so may change focus. The non parfocal lenses are called varifocal. Zoom lenses were available in both types, it was the manufacturers decision. Varifocal was cheaper and allowed greater flexibility i.e macro and wider apertures. And in your case, macro and a consistent aperture of f3.5

Perhaps parfocal lenses could be tweaked, but I doubt that varifocals could be simply due to the optical formula.

You dont really zoom while videoing do you?

[jonar]

Hi! The Minolta 35-70 3.5 should be parfocal to my knowledge. I would like like to zoom in set focus and back out like i'm used to, but maybe it isn't possible with this lens. After i adjusted the length on the adapter I have infinity focus correct on 70mm but not on 35mm.

[jonar]

Did another try with shimming the adapter and it seems like my first try was not so good. Now I have constant focus even though I lost infinity on some of my other lenses...

Cheers!