Is it possible to make an autofocus mirror lens?

Started Nov 25, 2012 | Discussions thread
Senior MemberPosts: 1,177
Re: Is it possible to make an autofocus mirror lens?
In reply to TFD, 6 months ago

TFD wrote:

I own the Sony 500mm mirror with autofocus and since the Sony has in body stablization (there are also no stablized mirror lens) it is hand holdable, with good light.

Sadly not made anymore - but there is always ebay.

If 500mm AF is what you need, the only reason to consider a CAT lens is for its size. Good quality conventional lenses are more convenient to use (variable f stop) and, IMHO, give better results. However, I wanted a 500 for travel and the small size was appealing.

Focusing a MF 500 is a challenge -- holding it steady even more so. So the Minolta AF with IBIS is the best solution for those of us using A-mount. Before I bought one, I tried the old Minolta MD mount 500mm with a converter. The results with an adapter that allowed infinity focus (glass) were unacceptable and didn't activate the IBIS -- sold that to someone into m4/3. I then acquired another MD 500 which had been adapted to A-mount and was able to focus to infinity. Still no IBIS but I liked its small size and, at speeds over 1/350, I got reasonably sharp results -- still, in spite of its lovely, silky focusing helicoid, subjects don't 'pop' in and out of focus.

I could live without AF but I really wanted IBIS. I ordered a chip from China set to 500mm focal length and f8 which I intended to mount on the Minolta 500mm MF Reflex. What I didn't realize was the amount of amputation it would take. I also bought a Sigma 600mm which was sharp but rather low contrast -- and considerably larger than either the Minolta AF or MF.

My repair guy wants $100 each and unlimited time to mount the chips on the 500 and 600. The chips were $50 each. Had I understood what was involved, I probably would have opted for the Leitz MR-Telyt 500/8 and had it converted and chipped

but it is heavier and more expensive than the other two.

At this point, I'm planning to keep the Minolta MF for travel (unchipped) and the AF for the occasional 'job'. If someone wants the Sigma 600 MF A-mount (mint) and the unmounted chip, I'd sell them for $250 plus shipping. As for the Minolta MD 500 adapted to A-mount, I'd sell the lens (good glass, ugly adapter) and unmounted chip for $500 plus shipping.

As for the donuts, it depends on what you shoot. Backgrounds totally lacking in bright highlights are less of a problem though the bokeh isn't terribly attractive anyway. If you can deal with the size and weight of a conventional lens (like the Sony 70-400) you'll probably get better results than with any CAT. And don't forget, when it come to shooting at distance, atmospheric haze cuts sharpness considerably, regardless of the lens design.

Given that Sony seems to be abandoning the A-mount, the Sony a900/a99 may be the last cameras made that offer CAT AF with IBIS. If hand holding a 500 for action shots or BIF is what you do, they may be the only choices -- and damn the donuts.

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