FrankS
Registered User
Kim Coxon said:
Ah, yes. Thanks.
Why does the screw-mount exist?
- Thread starter Max Power
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Ah, yes. Thanks.
And amoung light comments that may have been taken differently I have to say that Bill has hit what came to my mind.
The Leica Screw Mount was introduced in the 1920s and remains compatible with cameras that are made today (is the R still in production?). There are better mounts, but there also are benefits to the LTM.
The Leica Screw Mount was introduced in the 1920s and remains compatible with cameras that are made today (is the R still in production?). There are better mounts, but there also are benefits to the LTM.
Max Power
Well-known
Post 5 is opaque; post 6 is insulting.
I was interested in knowing if anyone had any ideas about why screw-mounts were engineered as opposed to bayonet mounts, and futhermore, why they persist.
I'm not certain why my capacity (or lack thereof) to mount a screw-mount lens was called into question.
Bill, I like your answer about backward compatibility and consumer demand. It makes a lot of sense, at least in the M-bayonet world, to continue to make M39 mount lenses. You can always use an adapter to go from M39 to bayonet mount, but not the other way. The 50/1.5 Nokton I just bought from Stephen Gandy is screw-mount, so it can be used on a whole range of cameras, not just those with an M bayonet mount.
Makes good economic and marketing sense.
Kent
I was interested in knowing if anyone had any ideas about why screw-mounts were engineered as opposed to bayonet mounts, and futhermore, why they persist.
I'm not certain why my capacity (or lack thereof) to mount a screw-mount lens was called into question.
Bill, I like your answer about backward compatibility and consumer demand. It makes a lot of sense, at least in the M-bayonet world, to continue to make M39 mount lenses. You can always use an adapter to go from M39 to bayonet mount, but not the other way. The 50/1.5 Nokton I just bought from Stephen Gandy is screw-mount, so it can be used on a whole range of cameras, not just those with an M bayonet mount.
Makes good economic and marketing sense.
Kent
Gabriel M.A.
My Red Dot Glows For You
I can see post #5 pretty well. I don't think post #6 was questioning anything about you personally, if anything, I believe it was in response to the tongue-in-cheek comment #5 and also to Ernesto's (#3), which in no shape or form was insulting anybody either.
Should we begin putting disclaimers when we're making comments?
Disclaimer: it was a noninsulting, confused, rhetorical question.
Should we begin putting disclaimers when we're making comments?
Disclaimer: it was a noninsulting, confused, rhetorical question.
OK, now that this is behind us (right?)....
Max, it may be nothing other than that was how it was done. Prior to single frame 35mm cameras there were motion picture cameras which were screw mount. The bayonet mounts allow for easier changing, and as we later saw with the discontinuation of the M42 mount, the transfer of more info from the lens to the camera, which allowed cameras to advance in technology.
Max, it may be nothing other than that was how it was done. Prior to single frame 35mm cameras there were motion picture cameras which were screw mount. The bayonet mounts allow for easier changing, and as we later saw with the discontinuation of the M42 mount, the transfer of more info from the lens to the camera, which allowed cameras to advance in technology.
oftheherd
Veteran
bmattock said:
I think Yashica in their AX did rely on stop down even though it figured the exposure "automatically." I believe pentax, in their auto-exposure screw mount, the ES, and I know for sure the Fujica ST 901 and AZ, provided auto-exposure with open aperture metering. The did it with a ring around the lens mount that had a very smal pin which engaged a lug on the aperture selection ring on the lens. The lens screwed down to a point where it locked with a push release for removing the lens. But once you have the lens lined up right, you just keep screwing until it clicks. I still prefer the screw mount over the bayonet mount, but as I stated above, the only bayonet mount I have is the Yashica/Contax, so there may be some that are easy to use in low light. I didn't find the Canons to be easy when I was in the Army. I continued to use my gear for crime scene work.
Even the breechlock bayonet on my Super Press 23 requires the lens being aligned a certain way in order to line up the focusing cam inside the camera body. If you can't see the red marks on the body and lens, you just have to keep trying until you get it right.
ErnestoJL
Well-known
I don´t think we must put a disclaimer in front of anyone´s opinion, as it is just a personal opinion, and sometimes a joke about some comments, posts or facts.
Perhaps because of this, and knowing that my lack of a good written english knowledge would lead me to offend some one, I just write "IMO" or IMHO" in most of my posts.
In this thread as well as in many others, I´ve tried to give a technical opinion about what it was discussed. That´s perhaps why my opinions sometimes are a bit technically biased, and not allways showing my personal believes.
I think that M42 mount was just a kind of evolution over M39 mount, which allowed designers to have enough room to acomodate the SLRs mirror and new lenses.
And, besides of other facts, it allows me to make real a wild dream: to use a Helios 44 in a Contax with a special adapter...
Regards to all
Ernesto
Perhaps because of this, and knowing that my lack of a good written english knowledge would lead me to offend some one, I just write "IMO" or IMHO" in most of my posts.
In this thread as well as in many others, I´ve tried to give a technical opinion about what it was discussed. That´s perhaps why my opinions sometimes are a bit technically biased, and not allways showing my personal believes.
I think that M42 mount was just a kind of evolution over M39 mount, which allowed designers to have enough room to acomodate the SLRs mirror and new lenses.
And, besides of other facts, it allows me to make real a wild dream: to use a Helios 44 in a Contax with a special adapter...
Regards to all
Ernesto
Wimpler
Established
I actually find m42 screwmount handier than any bayonet mount. The only disadvantage is, when not tightly screwed in, it may come loose when it is not supposed to.
oftheherd
Veteran
Wimpler said:
Now that's a scary thought. I always snugged my up and it was never a problem for me though. Still, scary to think about.
back alley
IMAGES
while we're asking questions...i have a maybe dopey one.
why is the leitz bayonet mount called the m mount??
i'd like to know.
joe
why is the leitz bayonet mount called the m mount??
i'd like to know.
joe
David Murphy
Veteran
OK, let me weigh in a bit here as someone with some rudimentary mechanical design and metal shop experience. Machine shop and metal manufacturing technology was eminently capable of making a bayonet mount in 1930 -- no problem -- no major additional expense. Breech locking, bayonet locking, and other quick disconnect/connect fastening mechanisms had been well-documented and used for decades if not centuries by 1930 or so.
Screw mount is just dead simple however: you machine a reference surface and cut an inside thread (an easily repeatable lathe operation) . That's why some camera engineer in the days of yore back in Germany (at Leica) thought of it first and (at Leica or KW) put it down on a drafting board and took to an engineering meeting. Incidentally the predominant early SLR, the Exakta, came right after the Leica screw-mount and about the same time as early screw mount SLR's. The Exakta WAS (and is!) a bayonet mount system.
BTW in my humble opinion, screw mount was a solid engineering decision. Screw mount lenses work great to this day, CAN be changed quicky with experience, and DO in fact stand the test of time and wear. The advantages of bayonet or breech-locking lenses have been greatly exaggerated by a photo press that seems only want to want to hawk the latest products of the camera industry. I remember well back in the late 60's and early 70's it was all the rage in photo magazines to bash screw mount lenses and cameras.
Screw mount is just dead simple however: you machine a reference surface and cut an inside thread (an easily repeatable lathe operation) . That's why some camera engineer in the days of yore back in Germany (at Leica) thought of it first and (at Leica or KW) put it down on a drafting board and took to an engineering meeting. Incidentally the predominant early SLR, the Exakta, came right after the Leica screw-mount and about the same time as early screw mount SLR's. The Exakta WAS (and is!) a bayonet mount system.
BTW in my humble opinion, screw mount was a solid engineering decision. Screw mount lenses work great to this day, CAN be changed quicky with experience, and DO in fact stand the test of time and wear. The advantages of bayonet or breech-locking lenses have been greatly exaggerated by a photo press that seems only want to want to hawk the latest products of the camera industry. I remember well back in the late 60's and early 70's it was all the rage in photo magazines to bash screw mount lenses and cameras.
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FrankS
Registered User
back alley said:
Because it was introduced on the M3 camera? Why did they call it an M3, I don't know. The 3 is there because of the 3 framelines, I believe. The M might be there because of the M mount the camera came with. 😉
(circular logic at work)
RJBender
RFF Sponsoring Member
The first camera with the M42 mount was the Zeiss Contax S produced in the DDR in 1949. They show up on eBay frequently.
R.J.
R.J.
David Murphy
Veteran
Yes I believe this is correct, but there were screw mount SLR's made in the 30's that used a *different thread* (not M42). I can't remember the thread spec, but you can look it up on Google. I think these were made by Kamera-Werke in Dresden.
RJBender said:
RJBender
RFF Sponsoring Member
Yes, the Praktiflex from 1939 had a 40mm screw mount thread.
source: http://www.taunusreiter.de/Cameras/Praktiflex.html
R.J.
source: http://www.taunusreiter.de/Cameras/Praktiflex.html
R.J.
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oftheherd
Veteran
I don't think the "brick" was either Leica or M42. In fact, didn't it screw the "wrong" way?
Benjamin Marks
Veteran
Just another POV: in some ways a screw-mount is more secure than a bayonet. An M39 lens has to go through many rotations to actually fall off the camera. A faulty breach lock on a bayonet mount and your beautiful hunk of glass could be lying there, whimpering in the mud. I think it was a marketing thing, really, to discourage cross utilization of lenses among camera brands.
FrankS
Registered User
I still think it was the simplest solution, so it was chosen. Western culture only later became obsessed with "quick and easy".
ampguy
Veteran
I think m42 screw mount with good adapters is a great way to get into some good lenses.
I have a cheap K-mount SLR, and 2 amazing m42 lenses, a Sigma 18mm 3.4, and a Vivitar 35 f1.9 that share an m42 to k adapter which stays on the body (I hope these are my last lenses for this slr ... ).
But to my point, to have bought these quality of lenses in k-mount, if they even exist, would have cost much much more.
Also, in researching these lens, I have found folks are using these (with appropriate adapters) to good use on even their DSLR's. It's great glass, just on an old funky platform, which is why these adapters are so important.
I have a cheap K-mount SLR, and 2 amazing m42 lenses, a Sigma 18mm 3.4, and a Vivitar 35 f1.9 that share an m42 to k adapter which stays on the body (I hope these are my last lenses for this slr ... ).
But to my point, to have bought these quality of lenses in k-mount, if they even exist, would have cost much much more.
Also, in researching these lens, I have found folks are using these (with appropriate adapters) to good use on even their DSLR's. It's great glass, just on an old funky platform, which is why these adapters are so important.
doubs43
Well-known
Interestingly I've used screw-mount lenses on Leicas and SLRs since the 1960's and never have I cross-threaded one in spite of trying to start them at all sorts of odd angles. Anyone who can cross-thread them is far more talented than I, that's for sure!
As already pointed out, the Kine Exakta was introduced in the mid-1930's and was a bayonet mount camera. The Contax rangefinder cameras also dated from the early 1930's and used a bayonet mount. It's incorrect to think that the idea of a bayonet mount didn't come along early in the interchangeable lens game. It did.
It's also been mentioned that the Contax SLR was the first to use the 42mm or M42 screw-mount system but it was the Asahi Pentax that really put the "universal" screw-mount M42 on the map. The East German Praktica adopted the same mount, helping to make the "universal" bit true. The Japanese, of course, manufactured numerous camera marques that used the M42 mount and the after-market lens makers in Japan and Europe added untold thousands of lenses to the available selection.
Is the M42 slower to change than a bayonet mount lens? Yup, it is... but that's about the only disadvantage the system has. The M42 Asahi Takumar lenses take a back seat to no one in mechanical quality or optical performance. To them you can add Yashinon, Rikenon, Mamiya-Sekor, Carl Zeiss Jena, Pentacon, Meyer and more who turned out lenses that range from very good to excellent.
Everyone has their own ideas about the camera system they should own and choice is what it's all about. However, it's a mistake to think that other cameras and lenses don't measure up. The M42 cameras and lenses are alive and well. I enjoy mine just as I also enjoy my rangefinders. When you need to go past 135mm, the M42 offers a lot and so do the bayonet mount SLRs.
Walker
As already pointed out, the Kine Exakta was introduced in the mid-1930's and was a bayonet mount camera. The Contax rangefinder cameras also dated from the early 1930's and used a bayonet mount. It's incorrect to think that the idea of a bayonet mount didn't come along early in the interchangeable lens game. It did.
It's also been mentioned that the Contax SLR was the first to use the 42mm or M42 screw-mount system but it was the Asahi Pentax that really put the "universal" screw-mount M42 on the map. The East German Praktica adopted the same mount, helping to make the "universal" bit true. The Japanese, of course, manufactured numerous camera marques that used the M42 mount and the after-market lens makers in Japan and Europe added untold thousands of lenses to the available selection.
Is the M42 slower to change than a bayonet mount lens? Yup, it is... but that's about the only disadvantage the system has. The M42 Asahi Takumar lenses take a back seat to no one in mechanical quality or optical performance. To them you can add Yashinon, Rikenon, Mamiya-Sekor, Carl Zeiss Jena, Pentacon, Meyer and more who turned out lenses that range from very good to excellent.
Everyone has their own ideas about the camera system they should own and choice is what it's all about. However, it's a mistake to think that other cameras and lenses don't measure up. The M42 cameras and lenses are alive and well. I enjoy mine just as I also enjoy my rangefinders. When you need to go past 135mm, the M42 offers a lot and so do the bayonet mount SLRs.
Walker
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