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Auto-focus adapter for old MF lenses - IT WORKS !
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PostPosted: Thu May 21, 2015 11:30 am    Post subject: Auto-focus adapter for old MF lenses - IT WORKS ! Reply with quote
I know, it sounds crazy, but it actually works!!! Surprised Very Happy

I thought about it long time ago but I've never considered it really feasible. Few weeks ago someone on this forum posted a link to some old Russian lenses remounted in Minolta AF lens bodies and they seemed to work in AF mode. That made me think that my old project has a chance to actually work and I decided to try it. I have a 35-70 Minolta AF lens that I didn't use and intended to sell but the prices are so low that it's not really worth selling. So, I've dismantled it, took out all its glass parts and the diaphragm, re-mounted the remaining parts and tried it on my MEX-7 with the LA-EA4 adapter. At first it didn't work - the camera didn't recognize it. But the next day, when cleaning my working space, I've discovered that I forgot to mount a thin spacer beneath the lens mount. I fixed it in place and...BINGO! Very Happy - the camera recognizes the lens and the AF mechanism works snappy.

That's the AF adapter made from my 35-70 Minolta AF lens:


And here I'm presenting you the first ~80 years old Auto-focus TT&H 5 inches anastigmat lens on my NEX-7:





And here are the first AF tests with the old lens:




Exceeding my expectations the AF is working well and is quite snappy.

The work is not finished, I still have to make adjustments and better mounts for the old lenses I want to use with it, but I can already draw some conclusions:

- Only lenses with a FL >~95 mm can be adapted with the adapter I made from the 35-70 Minolta AF lens. I've tried the 101 mm Ektar with it and it focuses to infinity.
- Adapted lenses shouldn't weight to much because half of the Minolta AF helicoid is made of plastic.
- Lenses with a longer than 135 mm FL shouldn't be used because of the same reason above. I've tried my 135 mm Hektor lens and it works well.
- The lens shouldn't be used in low interior light with the lens diaphragm closed more than f/8 - not sufficient light for AF.
- The zoom mechanism extension of the Minolta AF lens can be, very convenient, used for close up, as in the tests above. Very Happy

My conclusion so far is that this adapter does a fairly good job in auto-focusing old MF lenses but it is not a complete AF solution. That's because the AF extension of the lens is not long enough for closer focusing.
The best way to use it is to make a quick draft manual focus using its zoom ring first and then let the adapter do the precise AF. It's quite quick and precise this way - as snappy as the initial Minolta AF lens was.

I'll further develop and tune it up, add other lenses and continue to post here my conclusions.


PostPosted: Thu May 21, 2015 12:02 pm    Post subject: Reply with quote
Genius Dan!! I'm impressed, VERY well done!


PostPosted: Thu May 21, 2015 2:33 pm    Post subject: Reply with quote
Amazing work!


PostPosted: Thu May 21, 2015 3:30 pm    Post subject: Reply with quote
Great idea you have there and nice result.


PostPosted: Thu May 21, 2015 7:13 pm    Post subject: Reply with quote
Yes! Well done indeed!


PostPosted: Thu May 21, 2015 7:25 pm    Post subject: Reply with quote
Very cool Very Happy
IQ on the TayHob is fantastic too!


PostPosted: Fri May 22, 2015 6:53 am    Post subject: Reply with quote
wow Shocked


PostPosted: Fri May 22, 2015 10:59 am    Post subject: Reply with quote
Great job and inventivity !
Congrats Dan.


PostPosted: Fri May 22, 2015 1:04 pm    Post subject: Reply with quote
There was a topic on the sony-club.ru about a similar concept. That guy used a minolta AF 50/1.7 and the J-9 lens block, it actually worked and focused well on his a-mount cameras. I can't find the topic now, since it was posted a few years ago, anyway very nice ideas.

PS
Found a video of the J-9 https://www.youtube.com/watch?v=71KMNO4PWjk


PostPosted: Sat May 23, 2015 4:52 am    Post subject: Reply with quote
Thank you gentlemen for the kind words.

RTI
Yes, a link to that video posted on this forum few weeks ago made me think that such an adapter might actually work.


PostPosted: Fri Jul 31, 2015 6:14 am    Post subject: Reply with quote
I've also done some tests in that area, but never finished, since too much mechanical work would be needed.

Minolta 35-70/3.5-4.5 was used as donor, and it was focusing 500mm/F8 preset lens. In bright sunlight it worked just fine.


PostPosted: Fri Jul 31, 2015 8:19 am    Post subject: Reply with quote
CuriousOne wrote:
In bright sunlight it worked just fine.

I've noticed that too - f/8 is just about the limit for using the auto-focus.

Wasn't the 500mm too heavy?
I was surprised to see that the AF mechanism of the 35-70 did focus my 150mm f/2.8 Elmaron, a quite heavy lens, but I was afraid to try heavier lenses. For heavier lenses (in fact for any lens) with longer flange distance is better to use some AF A-mount macro rings as spacers to make the AF mechanism stay closer to the lens.

I am now at the mk4 AF adapter - 2 with 35-70 as donor and 2 with 50/1.7.
The 50/1.7 AF mechanism is better because it's all-metal. Lighter lenses, like the projection Elmaron 120mm and Diaplan 80mm, do auto-focus quite quick and precise with the 50/1.7 AF mechanism.

The Mk4 project is a Helios 44-2 preset completely remounted in the body of a Minolta AF 50/17. It is not yet completed, it needs some more lathe work to be done, but it seams that it can be made to focus infinity.

IMO, other M42 preset lenses could be nicely adapted, too - the preset mechanism is placed at the front side of the lens and therefor the diaphragm ring is accessible. But I don't have much experience with preset lenses (I usually avoided them).

Which preset lenses do you think would be worth remounting in an AF body? It would be nice to have a small set of AF M42 lenses.
The main requirement is that the lens body shouldn't be shorter than the body of the Minolta AF 50mm f/1.7.


PostPosted: Mon Aug 03, 2015 4:24 pm    Post subject: Reply with quote
Now that's a nice hack. Joining three generations of equipment. Only a nice 35-70 had to die for it.
You may not even need AF, the focus dot and A mode can be useful too (glorified chip adaptor)

If I understand correctly you can't use M42 lenses (except for macro) since their rear would have to fit the A mount rear to reach infinity?


PostPosted: Mon Aug 03, 2015 8:07 pm    Post subject: Reply with quote
buerokratiehasser wrote:

You may not even need AF, the focus dot and A mode can be useful too (glorified chip adaptor)

You are right, in most cases you may not need AF. It was(is) more a kind of a challenge. But in the cases you need to be quick the AF is very convenient.
buerokratiehasser wrote:

If I understand correctly you can't use M42 lenses (except for macro) since their rear would have to fit the A mount rear to reach infinity?

The flange distance of the M42 mount is 45.46mm and for Minolta AF it is 44.5mm. There is no moving mirror on my LA-EA4 and the difference could be sufficient for infinity focus if the lens is not mounted with an adapter but instead it is "transferred" in the body of the Minolta AF lens. Not simple to do it but, IMO, possible.


PostPosted: Mon Aug 03, 2015 8:40 pm    Post subject: Reply with quote
Congrats!!


PostPosted: Tue Aug 04, 2015 7:01 am    Post subject: Reply with quote
Yes, that's what I thought, you'd have to rebuild the lens in the victim, not sure whether changing the rear plate with A mount one would be less hassle.

Not only is the focus dot and A-mode useful, it also means the poor plastic shell and AF gear isn't stressed (you could perhaps even mount the shell to a large lens and turn the shell not the lens body)


PostPosted: Wed Aug 05, 2015 11:33 am    Post subject: Reply with quote
You might don't know, but Minolta's and Sony's AF motors are so powerful, that a lot of sigma lenses get stripped gears when used with them.


PostPosted: Sat Aug 08, 2015 7:51 am    Post subject: Reply with quote
Attila wrote:
Congrats!!

Thaks Attila.


PostPosted: Mon Aug 24, 2015 2:35 am    Post subject: Reply with quote
Edited

Last edited by bernhardas on Sat Apr 02, 2016 8:12 pm; edited 1 time in total


PostPosted: Sun Aug 30, 2015 8:43 am    Post subject: Reply with quote
The Jupiter-11 would fit nicely.

I have been trying this for a while with a Minolta 35-80, it works but all the lenses I wanted to use are too heavy as they are all-metal projection lenses.

Nice work Dan.


PostPosted: Sun Aug 30, 2015 1:11 pm    Post subject: Reply with quote
amazing, dan.


PostPosted: Sun Aug 30, 2015 1:33 pm    Post subject: Reply with quote
Thank you bernhardas, bluecoast and Ian. Thank You Dog

The housing of the 50mm f/1.7 is much better in handling heavier lenses. But only the older 50/1.7 lenses have an all metal helicoid. The latter 50/1.7 and 50/1.7 RS have half metal - half plastic helicoids, like all non-G zooms.
My all metal helicoid from the 50/1.7 can handle well (even it's not very happy with it) my 200 f4 Visoflex Telyt head even the big 150/2.8 Elmaron. But it really shines with old Folder or Larger Format not-too-heavy lenses and with projection lenses like THE 80mm Diaplan or the 120mm Elmaron.

I've finished the re-housing of the 58/2 Helios 44-2 in the Minolta AF body of the 50/1.7 and it auto-focuses just as quick and accurate as the initial Minolta 50/1.7. I'm quite pleased with it. I'll try to make a small film showing the auto-focus speed and accuracy.
The other contenders for rehousing are the Jupiter 9 lens and, as you suggested Ian, the Jupiter-11.
How about wider M42 preset lenses lenses? which one you suggest, Ian?
The contenders must have a good enough IQ to deserve the expense.


PostPosted: Sun Sep 06, 2015 9:41 pm    Post subject: Reply with quote
I'm not sure what to suggest Dan, most presets wider than 35mm are not very good as it was the early days of wide angle lens design.

You can look for the wider Schneider Cinelux and Cine Xenon projector lenses, awesome IQ but wider than 45mm (they go down to 24mm) the back focus is too short for A mount. I have 30 and 37.5mm Cineluxes and have to use them on my NEX. The 45 and longer ones I use on the A850.
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