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10-17-2019, 08:15 PM   #1
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Mount focusing DSLR for vintage lenses

I have been thinking about this idea of a camera dedicated exclusively to vintage glass. It's just a matter of designing a mount that can be extended away from the sensor as the camera focuses. I've seen this on L/M to S/E adapters from two different brands and this could certainly be implemented inside a Pentax camera.
Minimum focusing distance would also be reduced once the lenses are set at their longest extension. That would work similarly to the P 1.7 AF adapter.
• It should not need weather sealing since those lenses wouldn't benefit from it (a reason perhaps to brand it as Ricoh).
• Its sensor resolution should match that of the best lenses up to the A series and be optimized for lenses that were designed to be used on film that consisted of different layers (color film). Maybe even perhaps a monochrome version like a very well known premium german brand has done in the past.
• The design and construction should match the M42 to K mount transition era. Metal and tough build. Also a retractable push pin actuator used in combination with the already available adapter.
• Threaded cable release, mechanical DOF preview, aperture readout, manual MLU (which could also mean using non-retrofocus lenses released with the camera to beat the mirrorless hype).
• Hybrid viewfinder (switchable between optical/electronic).

I mean, even the next generation of Pentax digital medium format could benefit from at least the last two suggestions. Having 17 and 23 mm lens options would be nice. And that bulk of a camera is basically just empty space.

Should we be starting a petition? Who's taking orders?



10-19-2019, 05:55 AM   #2
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An interesting idea. I would like the body to be lighter in weight than the current Pentax DSLRs, to make it easier to focus with magnified live view. Doing this on a K-1 is not fun since i have to hold the camera out in front with all its weight in order to see the screen.
11-25-2019, 01:07 PM   #3
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There's nothing new under the sun, and this has been done, in the shape of the Contax AX 35mm SLR. So you are right, it's quite possible. Contax, with different design constraints because it was a film camera, chose to move the film plane and shutter back and forth. I think that moving just the lens mount as you have suggested would be an easier answer with a digital camera. The review at the link goes into quite a lot of detail that is relevant to your ideas; it's well worth a look.
11-26-2019, 06:16 AM   #4
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If you gave up on it being a DSLR and went mirrorless, you would be where you need to be,

Or simply go to canon. The diameter of their mount will make accepting any SLR vintage lens, when combined with their short registration distance.

The only thing canon doesn’t do, is accept their breach mount.

If you want one adaptor to “do it all, you need to start off with not only the 1.7x converter element like Pentax do with the AFA but also a retro focus group to get back to base focal length. This is a lot of glass to add, which will only add to the issues already present in the lenses.

I think going mirrorless is the way for using any vintage glass, because the registration distance let’s you do it

11-29-2019, 01:59 AM   #5
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Slight caveat that presumably a moving-mount focus would be sub-optimal for those lenses with floating elements. Not sure how many of those exist, and one could focus manually anyway. And it would have to be super-precise for wide angles, and have a long throw for telephotos...

+1 for aperture sensing, it really bugs me when all my vintage images show f/0.

Cheers

Jonathan
12-03-2019, 02:17 PM   #6
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QuoteOriginally posted by wstruth Quote
An interesting idea. I would like the body to be lighter in weight than the current Pentax DSLRs, to make it easier to focus with magnified live view. Doing this on a K-1 is not fun since i have to hold the camera out in front with all its weight in order to see the screen.
Something similar, but FF, to the K-01 would be what you need, since the pentaprism and mirror is what makes an DSLR a lot heavier. I mean, the P67 is a world of a difference when using the flip up viewfinder vs. the regular or metering prisms.

12-05-2019, 09:47 AM   #7
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This had occurred to me also. Basically a built in auto fine-focus mechanism based on a small amount of movement at the mount for primarily MF lenses. Would be something different, an interesting USP.

12-05-2019, 10:15 AM   #8
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QuoteOriginally posted by marcusBMG Quote
This had occurred to me also. Basically a built in auto fine-focus mechanism based on a small amount of movement at the mount for primarily MF lenses. Would be something different, an interesting USP.
Exactly. For WA lenses, that would mean basically full AF, and work like the 1.7 AF adapter (without the magnification and light loss) for manual teles.

12-05-2019, 10:22 AM   #9
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QuoteOriginally posted by h4yn0nnym0u5e Quote
Slight caveat that presumably a moving-mount focus would be sub-optimal for those lenses with floating elements. Not sure how many of those exist, and one could focus manually anyway. And it would have to be super-precise for wide angles, and have a long throw for telephotos...



+1 for aperture sensing, it really bugs me when all my vintage images show f/0.



Cheers



Jonathan
You're right, but how many people have a K 28/2 at hand? I mean, it can't be perfect in every case, but at least in general. Most people would be using it with a compact 28mm up to a standard ~50mm.
Also, about the aperture sensing, I think it could be done optically, perhaps in infrared (with a half press momentary activation only, so as to not ruin IR photography) or ultrasound/echo in lieu of a mechanical/electrical feeler. Depends on what's cheaper.

Last edited by torashi; 12-05-2019 at 10:30 AM.
12-06-2019, 10:15 AM   #10
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QuoteOriginally posted by h4yn0nnym0u5e Quote
Slight caveat that presumably a moving-mount focus would be sub-optimal for those lenses with floating elements. Not sure how many of those exist, and one could focus manually anyway. And it would have to be super-precise for wide angles, and have a long throw for telephotos...

Cheers

Jonathan
The Contax system I posted about above had lenses with floating elements, and the user (he says) would get the focus close manually, and then fine tune with AF. Not ideal, but I suppose it depends on the priorities of the moment. There's more on this at the link, but it's apparently reasonably practical.

I agree on the wideangle V telephoto requirements. I think the maximum extension would be governed by wide angle needs, especially as wide lenses are harder to focus manually; it would be of more use for shorter lenses.
12-06-2019, 01:42 PM   #11
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QuoteOriginally posted by torashi Quote
You're right, but how many people have a K 28/2 at hand?
Now, I wonder what made me think of that...
12-06-2019, 02:07 PM   #12
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QuoteOriginally posted by torashi Quote
Something similar, but FF, to the K-01 would be what you need, since the pentaprism and mirror is what makes an DSLR a lot heavier. I mean, the P67 is a world of a difference when using the flip up viewfinder vs. the regular or metering prisms.
But an FSLR needn't be that heavy, and it still has the pentaprism and mirror... It'd be interesting to know the weight budget for a DSLR vs an FSLR, to see where the savings could be made.

<ot> I think I would actually seriously consider a totally retro body for legacy lenses - all mechanical apart from the sensor and metering, something like an MX with a FF sensor in place of the film. No AF, just bring back the split screen and microprisms. No IBIS. No flash. No GPS (I'd miss that, but needs must...). If there's a self-timer, it's mechanical - otherwise you start "needing" to add solenoids... Battery fits where the film went, electronics in the take-up spool area and maybe across the back. Possibly allow for a grip attachment so long as it adds (near) zero size and weight to the basic body; otherwise, just carry a spare battery with you, you do that anyway.
</ot>

We now return you to your original discussion...

Cheers

Jonathan
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