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11-18-2019, 05:32 PM   #1
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Leica m39 crew type lens on the pentax 645

It has come to my attention that fotodiox sells an M39 screw type lens to pentax645 mount adapter. Also the Leica m45 50mm f1.8 lens sells for less than $100 on ebay. It doesn't seem intuitive as the m39 lens is a small rangefinder lens. On the other hand it was for a 35mm camera. I'm very tempted to buy this combination to have a f1.8 50mm lens for my 645. Anyone have any thoughts?

11-18-2019, 07:41 PM   #2
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Yes, be careful. LTM (Leica thread mount, incorrectly called M39 by some), M39 and Leica Visoflex are not the same thing. They do fit, but the threads might get damaged, and there is no guarantee that they'll screw on properly and that the lens' axis be aligned with the film/sensor plane.
I inherited a Schneider 4/50mm macro lens for large format. It's used mounted on a shutter on a cone lensboard so as not to interfere with lighting. It comes in an enlarging lens box screwed on to an M39 adapter, which is standard in some enlargers.
The adapter you're suggesting, if it's M39, could come in handy for using these lenses on the P645 system, albeit one would need macro rings, helicoid or the bellows to make it more versatile and not be limited to just one magnification.

Last edited by torashi; 11-18-2019 at 07:53 PM.
11-18-2019, 07:48 PM - 1 Like   #3
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Well, as it turns out, Fotodiox has a neat little guide to all the different mounts. Check it out:
https://fotodiox.freshdesk.com/support/solutions/articles/17000083341-m39-l3...sm-whats-what-
Visoflex has a very long flange focal distance; longer than Pentax's 645 mount. That is the reason this adapter exists, albeit I haven't seen it in stock. It's perhaps a special order item.
11-19-2019, 05:42 AM   #4
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QuoteOriginally posted by torashi Quote
Well, as it turns out, Fotodiox has a neat little guide to all the different mounts. Check it out:
https://fotodiox.freshdesk.com/support/solutions/articles/17000083341-m39-l3...sm-whats-what-
I had no idea it 39mm was that complicated. Thanks for the info and link.

11-19-2019, 08:42 AM - 1 Like   #5
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In case any are wondering what a Visoflex actually is (not everyone has come across one, in this day and age), it was a nifty adapter to turn a Leica rangefinder body into an SLR.

The Visoflex housing had a reflex mirror inside, and a viewfinder on top. Screwed onto the Leica body, you now had a rather kludgy SLR. You could put your regular rangefinder lens on front, but with all that extension, it was usable only for super close ups (not that wasn't a selling feature). But Leica made special lenses for the Visoflex, that accounted for all that extra extension, and could focus to infinity. Naturally these were telephoto lenses - which made up for the main shortcoming of the rangefinder system: they were great with wide and normal lenses, but were poor with longer tele lenses. Solution, turn your Leica into an SLR of course.

Early Visoflex housings were in thread mount, but later ones were for Leica M mount cameras. I have a 200mm Telyt in Visoflex mount, even though I don't have a Leica or Visoflex. But with adapters it makes a wonderful tele lens on a current DSLR. In fact, I consider it one of the best lenses in that focal length range I've ever used, so long as you don't mind the manual focus and all the adapters.
11-19-2019, 09:31 AM   #6
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QuoteOriginally posted by Ontarian50 Quote
In case any are wondering what a Visoflex actually is (not everyone has come across one, in this day and age), it was a nifty adapter to turn a Leica rangefinder body into an SLR.

The Visoflex housing had a reflex mirror inside, and a viewfinder on top. Screwed onto the Leica body, you now had a rather kludgy SLR. You could put your regular rangefinder lens on front, but with all that extension, it was usable only for super close ups (not that wasn't a selling feature). But Leica made special lenses for the Visoflex, that accounted for all that extra extension, and could focus to infinity. Naturally these were telephoto lenses - which made up for the main shortcoming of the rangefinder system: they were great with wide and normal lenses, but were poor with longer tele lenses. Solution, turn your Leica into an SLR of course.

Early Visoflex housings were in thread mount, but later ones were for Leica M mount cameras. I have a 200mm Telyt in Visoflex mount, even though I don't have a Leica or Visoflex. But with adapters it makes a wonderful tele lens on a current DSLR. In fact, I consider it one of the best lenses in that focal length range I've ever used, so long as you don't mind the manual focus and all the adapters.
Sounds like a good option for the P645, or even the P67 if the image circle is big enough.

11-19-2019, 02:41 PM   #7
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Thanks all for the comments. Seems the adapter I ordered is for the visoflex m39 lens to mount on a 645, but the lens I ordered was a Canon m39 lens, not the same as the visoflex M39. I'm not hopeful and I guess I lost some money unless I can return the items. The visoflex lenses are as expensive as Pentax 645 film lenses, and none of the visoflex lenses are a fast f1.8 like the Canon m39 I ordered.

11-20-2019, 09:02 AM   #8
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QuoteOriginally posted by torashi Quote
Well, as it turns out, Fotodiox has a neat little guide to all the different mounts. Check it out:
M39 / L39 / LTM / LSM - Whats What? : Fotodiox Inc. USA
Visoflex has a very long flange focal distance; longer than Pentax's 645 mount. That is the reason this adapter exists, albeit I haven't seen it in stock. It's perhaps a special order item.
Thanks for the reference to the table. Maybe you can help me deciper it. The lens I ordered is an LTM lens. On the chart it lists the same pitch and TPI as the visoflex lens, therefore the visoflex adapter. The only difference is the FFD. For the LTM lens I ordered it is 28.8mm, but for visoflex lens the adapter is made for the FFD is 91.3 mm. Does that mean the LTM lens will be about 2-1/2 inches further away from the sensor than it should be? Would that render any sort of focusing impossible?

---------- Post added 11-20-19 at 09:06 AM ----------

QuoteOriginally posted by Cipher Quote
It might work as an extreme macro but not for any non-macro use.

A m39 to m42 adapter won't focus to infinity.

There are m39 to Pentax Q adapters and they work very well (I have two of them.)

UPDATE: That adapter is for a VISOFLEX M39, not a regular M39
Thanks for that info! So worst case I can exchange the adapter and use the lens on my Q, even if it doesn't focus at all on my 645Z.
11-20-2019, 10:34 AM   #9
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QuoteOriginally posted by bobspez Quote
Thanks for the reference to the table. Maybe you can help me deciper it. The lens I ordered is an LTM lens. On the chart it lists the same pitch and TPI as the visoflex lens, therefore the visoflex adapter. The only difference is the FFD. For the LTM lens I ordered it is 28.8mm, but for visoflex lens the adapter is made for the FFD is 91.3 mm. Does that mean the LTM lens will be about 2-1/2 inches further away from the sensor than it should be? Would that render any sort of focusing impossible?

---------- Post added 11-20-19 at 09:06 AM ----------


Thanks for that info! So worst case I can exchange the adapter and use the lens on my Q, even if it doesn't focus at all on my 645Z.
Well... the Canon lens will focus if put onto the Fotodiox adapter and put on a 645, but only really, really close. Giving a 50mm lens 50mm of extension away from the film plane makes it focus 1:1 - that's before you've turned the focus ring away from infinity. The M39 lens wants to be set 28.8mm from the film plane for correct infinity focus. The adapter puts it 91.3mm away, so 62.5mm too much extension. So you're focusing closer than life size. On the plus side, all that extension will spread out the lens' coverage area, so it probably will cover the larger format to the corners.

But adapting a 35mm format lens to 645 usually won't work normally. If you could put that lens 28.8mm away from the 645 film plane, or digital sensor, coverage will fall short, and you'll have dark corners.
The exception to that is sometimes found in old-school telephoto lenses for 35mm that do have larger coverage than needed, and can be adapted to medium format - which I believe is why the Visoflex to Pentax 645 adapter exists. Those old long Telyt lenses (400mm or so) were simple achromats, and had large coverage.
11-20-2019, 02:54 PM   #10
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QuoteOriginally posted by bobspez Quote
Thanks for the reference to the table. Maybe you can help me deciper it. The lens I ordered is an LTM lens. On the chart it lists the same pitch and TPI as the visoflex lens, therefore the visoflex adapter. The only difference is the FFD. For the LTM lens I ordered it is 28.8mm, but for visoflex lens the adapter is made for the FFD is 91.3 mm. Does that mean the LTM lens will be about 2-1/2 inches further away from the sensor than it should be? Would that render any sort of focusing impossible?

---------- Post added 11-20-19 at 09:06 AM ----------


Thanks for that info! So worst case I can exchange the adapter and use the lens on my Q, even if it doesn't focus at all on my 645Z.
Well, it's going to be a tricky one. You'll only be able to shoot macro. And the focusing helicoid of the lens won't make a big enough difference for the magnification you're going to get. One other thing is, that your lens is optimized for infinity, which means it won't perform well for macro, unless you reverse it. Since the mount is just a thread, it could work -under the condition that there's no interference with any parts inside the adapter or camera thereafter- keeping in mind you'll be limited to setting the desired aperture before mounting it on the camera.

Last edited by torashi; 11-20-2019 at 04:23 PM.
11-21-2019, 09:58 AM   #11
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Thank you Torashi and Ontarian50. It should be interesting. I will get the lens from Japan in a couple of weeks, and the adapter should be here by then. I will post my results here.
11-23-2019, 04:29 PM - 1 Like   #12
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QuoteOriginally posted by bobspez Quote
Thank you Torashi and Ontarian50. It should be interesting. I will get the lens from Japan in a couple of weeks, and the adapter should be here by then. I will post my results here.
Cool, can't wait to see them. Crossing my fingers so there won't be any mechanical interference!

11-29-2019, 07:08 PM   #13
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QuoteOriginally posted by torashi Quote
Cool, can't wait to see them. Crossing my fingers so there won't be any mechanical interference!
Not there yet because Amazon sent me the pentax 67 adapter rather than the pentax 645 adapter. I have to return that adapter and then when I get my refund order the correct adapter. This time I'll go through Fotodiox direct.

But I did try to take a macro pic by holding the adapter up to the 645 (it's bigger than the camera opening), and take a shot with the lens wide open to f1.8. I'm thinking I can do better with the right adapter, a tripod and trying different f-stops. At least I got an image which I wan't sure I would be able to get.

The first image (the blue sandisk card) is with the M39 lens and adapter. f 1.8, 1/50 sec. iso-100, handheld, illumination is a 60 watt equiv. desk lamp.

The second image (the gold sandisk card) is with the Pentax 645 SMC 120mm macro lens. f4.0 , 1/50 sec. iso-100, handheld, illumination is a 60 watt equiv. desk lamp.

The third image is a comparison of the two lens sizes.

I'll post another image when I get the new adapter.
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12-01-2019, 11:29 AM   #14
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QuoteOriginally posted by bobspez Quote
Not there yet because Amazon sent me the pentax 67 adapter rather than the pentax 645 adapter. I have to return that adapter and then when I get my refund order the correct adapter. This time I'll go through Fotodiox direct.

But I did try to take a macro pic by holding the adapter up to the 645 (it's bigger than the camera opening), and take a shot with the lens wide open to f1.8. I'm thinking I can do better with the right adapter, a tripod and trying different f-stops. At least I got an image which I wan't sure I would be able to get.

The first image (the blue sandisk card) is with the M39 lens and adapter. f 1.8, 1/50 sec. iso-100, handheld, illumination is a 60 watt equiv. desk lamp.

The second image (the gold sandisk card) is with the Pentax 645 SMC 120mm macro lens. f4.0 , 1/50 sec. iso-100, handheld, illumination is a 60 watt equiv. desk lamp.

The third image is a comparison of the two lens sizes.

I'll post another image when I get the new adapter.
Well, from your exposure values, I can tell that the sensor is getting the same illumination, so I would just stick to using the 120/4 macro, unless you want less depth of field or are looking for a challenge.

12-02-2019, 09:49 AM - 1 Like   #15
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QuoteOriginally posted by torashi Quote
Well, from your exposure values, I can tell that the sensor is getting the same illumination, so I would just stick to using the 120/4 macro, unless you want less depth of field or are looking for a challenge.
Yes to both of those. Plus the reduced weight makes it easier to hold. I just ordered a new adapter from Fotodiox for about $18 less due to a black Friday sale. Amazon should process my refund on the first adapter withing a week or two. I'll post my efforts when I get the new adapter.
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