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07-19-2021, 02:03 PM   #16
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The above image is taken from here: An early swansong? Reviewing the CONTAX AX: autofocusing manual lenses | EMULSIVE
A lot of info about the camera, and by the way, they're also mentioning the restrictions for lens designs - e.g. FREE elements not being effective unless you prefocus.

07-19-2021, 03:43 PM   #17
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QuoteOriginally posted by Kunzite Quote
The above image is taken from here: An early swansong? Reviewing the CONTAX AX: autofocusing manual lenses | EMULSIVE
A lot of info about the camera, and by the way, they're also mentioning the restrictions for lens designs - e.g. FREE elements not being effective unless you prefocus.
Right, This post actually triggered me to start this thread. If something designed/made more than 25 years ago sill could be used with some positive result maybe whole idea is not entirely stupid.
07-20-2021, 01:31 AM   #18
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QuoteOriginally posted by jumbleview Quote
Right, This post actually triggered me to start this thread. If something designed/made more than 25 years ago sill could be used with some positive result maybe whole idea is not entirely stupid.
The problem of a design like this is the complexity that would lead to a very high price tag. Would you be interested to get a K1 II with this added if you had to pay $6000 for it?
The price may end up even more expensive as small number of customers would be interested by it. So the R&D cost may add a huge amount of cost on each unit.

It may have made some point back in the days when manual focus lenses where still manufactured. But to release a very expensive camera today optimized for manual focus lenses just do not make much sense.
07-20-2021, 07:38 AM   #19
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QuoteOriginally posted by jumbleview Quote
Right, This post actually triggered me to start this thread. If something designed/made more than 25 years ago sill could be used with some positive result maybe whole idea is not entirely stupid.
The positive part of this sort of design in today's world is that there would be far less mass to move. The Contax AX was, in essence, an entire camera built within another camera. In order for the AF of that camera to work, the entire film carriage had to be mobile. That meant the film holder and take up spool, as well as everything in between, and all the mechanical parts of the film advance had to be able to move.

Now, all that would have to be mobile is the sensor.

From a design perspective, this would be much easier, but with nearly 40 years of lens AF from all the major manufacturers and the millions of lenses to go along with it, it's not really a viable concept.

07-20-2021, 09:01 AM - 1 Like   #20
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QuoteOriginally posted by jumbleview Quote
Right, This post actually triggered me to start this thread. If something designed/made more than 25 years ago sill could be used with some positive result maybe whole idea is not entirely stupid.
Great point!

A big system design issue is whether to add cost to every lens in order to make the body more affordable. The decision is also affected by wanting to maintain backward compatibility to older lenses,

There are at least half a dozen subsystems that could be either built into the body or into each lens. Examples include:

Focus movement: one in-body mechanism to move the sensor or film versus every lens needing a motion stage. Large format cameras have in-body focus movement(the bellows). Smaller format cameras have typically used in-lens.

AF sensing: These have almost always been in-body with the exception of the first AF lenses that could be used on MF cameras (e.g., the Pentax 1.7X AF Adapter/teleconvertor).

AF motor: in-body screw drive was widely used until in-lens motors became feasible and better.

IR cut filter: These have always been in-body.

Anti-alias/optical low-pass filter: These have always been in-body, too. However, in theory, the much better solution is an AA/OLPF that is optimized for each lens. (Sharp lenses need strong filters, soft lenses need no filters. In-lens filters can also be optimized for aperture-sharpness effects and corner-softness effects.)

Shutter: in-body focal plane shutter versus in-lens leaf shutter.

Image stabilization: Pentax put this in the body. Other makers put it in their high-end lenses and forced you to buy stabilization at a high cost.

Last edited by photoptimist; 07-22-2021 at 05:51 AM.
07-20-2021, 11:48 AM   #21
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QuoteOriginally posted by Wheatfield Quote
The positive part of this sort of design in today's world is that there would be far less mass to move. The Contax AX was, in essence, an entire camera built within another camera. In order for the AF of that camera to work, the entire film carriage had to be mobile. That meant the film holder and take up spool, as well as everything in between, and all the mechanical parts of the film advance had to be able to move.

Now, all that would have to be mobile is the sensor.

From a design perspective, this would be much easier, but with nearly 40 years of lens AF from all the major manufacturers and the millions of lenses to go along with it, it's not really a viable concept.
On a Pentax DSLR it might not be much difference in mass as the whole SR mechanism with the sensor has to be moving. At least if wanting to keep image stabilization. Together with the OVF, mirror and shutter just like on Contax AX.

On a mirrorless camera without sensor stabilisation it could be done much lighter, but it would still add a lot to the size of the body.

But the main problem IMO with a moving sensor for focus is that it have to extend very long if you want full focus throw on lenses.
So for practcal reason it is not a concept you can uise for continous AF unless you add AF to the lens too.
Only for fine tuning focus on pre focused lenses. But on mirrorless it is so easy to focus manually anyway so I do not see much point in this.
07-22-2021, 03:02 AM - 1 Like   #22
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QuoteOriginally posted by photoptimist Quote
AF sensing: These have almost always been in-body with the exception of the first AF lenses that could be used on MF cameras (e.g., the Pentax 1.7X AF Adapter/teleconvertor).
Apologies for nitpicking (I do have to make my 7 posts for the day), but that doesn't sounds quite right. If by AF sensing you mean the focus detection (contrast or phase difference) module, that is still in the camera with Pentax. I believe that is true with the ME-F, too - although the lens is "special", containing the AF motor and batteries.

The Pentax 1.7X AF adapter just acts like an autofocus lens - a normal one, post the ME-F experiment. And of course, no AF lenses have AF on MF cameras - although all AF lenses with an aperture ring can be used on MF cameras; but there's no "AF sensing".

Unless I completely misunderstood what you meant.

07-22-2021, 05:49 AM   #23
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QuoteOriginally posted by Kunzite Quote
Apologies for nitpicking (I do have to make my 7 posts for the day), but that doesn't sounds quite right. If by AF sensing you mean the focus detection (contrast or phase difference) module, that is still in the camera with Pentax. I believe that is true with the ME-F, too - although the lens is "special", containing the AF motor and batteries.

The Pentax 1.7X AF adapter just acts like an autofocus lens - a normal one, post the ME-F experiment. And of course, no AF lenses have AF on MF cameras - although all AF lenses with an aperture ring can be used on MF cameras; but there's no "AF sensing".

Unless I completely misunderstood what you meant.
No apologies needed! When it comes to technical statements, all nits should be picked!

You are right about both the 1.7X AF adapter and ME-F/35-70 AF zoom.

The only example of a non-body solution for the AF sensor that I could easily find was this Nikon patent for pellicle/translucent mirror autofocus adapter to use current Nikkor DSLR lenses on a mirrorless camera.
07-22-2021, 08:24 AM - 1 Like   #24
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QuoteOriginally posted by photoptimist Quote
The only example of a non-body solution for the AF sensor that I could easily find was this Nikon patent for pellicle/translucent mirror autofocus adapter to use current Nikkor DSLR lenses on a mirrorless camera.
Sony had something like that - on the market.
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