autofocus for M lenses

[chip j]

https://www.ebay.com/itm/TECHART-Au...m=263371741569&_trksid=p2047675.c100008.m2219

 

[neilt3]

It has no place in a "35mm Cameras and Accessories " forum though .
The Only camera it fits are some digital Sony E-mount cameras .
It's of no use with any film camera .

Probably best mentioned in one of the hybrid or digital forums .
If you have a camera it's compatible with though it would be handy for adapting small primes via a second adapter . Contax CY to M-mount to E-mount for eg , small lightweight primes like the Olympus OM ones would also work well on it .

 

[AgX]

But as the basic idea would be applicable to a 35mm AF camera I chime-in nonetheless:

The description says it would work on any lens with apt mount.
But that cannot be possible. It may work with lenses of short FL, but not with lenses of long FL, as the adapter could not provide long enough extension.

 

[johnha]

Reminds me of the Pentax 1.7x AF teleconverter which allowed any manual focus K mount lens to be focussed automatically by a Pentax AF SLR (within limits and with a 1.7x conversion). It is still sought after today: https://www.pentaxforums.com/lensreviews/Pentax-Rear-Teleconverter-F-1.7x-Autofocus-Adapter.html

 

[AgX]

Up to 400mm!

 

[blockend]

It would be interesting to see an AF body mount, like a motorised Contax RF that could be adapted to any lens.

 

[AgX]

The description says it would work on any lens with apt mount.
But that cannot be possible. It may work with lenses of short FL, but not with lenses of long FL, as the adapter could not provide long enough extension.

I overlooked that the longest FL in M mount was 135mm, so it may work indeed.

 

[Tom Duffy]

The lens stays focused at infinity while the lens mount focuses. If you have an M lens with floating elements, the lens won't perform as well.

 

[AgX]

One could pre-focus then the lens at close distance.

 

[ic-racer]

Were you able to adapt this to a 35mm camera, or why is this thread here?

 

[neilt3]

Were you able to adapt this to a 35mm camera, or why is this thread here?

No , this adapter will only fit on the Sony E-mount digital cameras .
It can not be used with any film camera ( ever !).

 

[neilt3]

Reminds me of the Pentax 1.7x AF teleconverter which allowed any manual focus K mount lens to be focussed automatically by a Pentax AF SLR (within limits and with a 1.7x conversion). It is still sought after today: https://www.pentaxforums.com/lensreviews/Pentax-Rear-Teleconverter-F-1.7x-Autofocus-Adapter.html

Nikon and Sigma also made a similar device as a 1.6x AF teleconverter .

I think Nikon was first with the Nikon F manual focus lens to A/F body , then Sigma copied it to make a Nikon F to Minolta A-mount A/F converter and Minolta SR ( manual focus mount , A.K.A MD ) to Minolta A-mount A/F body .
All three work the the same . The lens unit inside it moves back and forward when the shutter release button is half pressed to enable auto focus .
As they have limited movement with anything other than wide angle lenses it's best to partially prefocus so only a bit of correction is needed .
I have all three and I use them from time to time with longer , faster primes , O.E.M , Tamron adaptall and M42 lenses .
They do quite a good job and work with some film cameras and some digital cameras .

I imagine the adapter in this thread would be used in the same manner , partially pre-focus and then let A/F take over .