David.Boettcher
Established
A 1933 and a 1935 manual which I looked in don't go into detail about lens changing, merely remarking that "The lenses are screwed moderately tight into the changing flange" and that's it.
But here is a scan of a page from an instruction manual for a IIIc, which does give a lot more detail about deploying and changing lenses.
As can be seen the only mention of the focussing lever is when attaching a lens to a body, where it says that the lens should be presented so that the focussing lever is in front of the viewfinder window. It doesn't mention the infinity catch, but the supposition must be that it is engaged, or else the location of the focussing lever would not be relevant.
The text does not mention, and the pictures do not show, the focussing lever / infinity catch being used in either deploying the lens (drawing out and locking or unlocking and collapsing) or removing and attaching a lens. If one of these actions were the primary purpose of the infinity catch, I think it would be described clearly, but in fact the infinity catch is not mentioned at all. The text says to remove the lens one should "grasp the lens close to the camera body" i.e. on the fixed part of the mount, not the focussing ring.
The infinity catch is described in a separate section on the next page. Its action is clearly described, but not its purpose. From this description it seems clear that the writer of the manual knew how it worked but did not know the reason for the infinity lock. E.g. he doesn't say "This is used for ... " or "This is useful when ... ".
In several sources it is reported that Barnack was a keen walker and probably liked to take landscapes. Perhaps he placed the "hockey stick" infinity locks on the early Leicas so that he could lock the lens on infinity and then not worry about it being disturbed from that setting by his walking activities. With a reasonable combination of shutter speed and aperture selected he could then walk freely, and take pictures just by looking through the viewfinder and pressing the shutter without having to adjust any setting on the camera at all. Because the hyperfocal distance varies with aperture, and hyperfocal focussing isn't really vital for distant landscapes, he just made a sensible compromise and chose infinity as the setting.
When interchangeable lenses were introduced it was only the short 3.5cm and 5cm which were given the focussing lever and infinity catch, I believe, and these lenses are the ones with great depth of field and relative insensitivity to focus compared to long lenses, these are the lenses most amenable to this kind of set-and-forget treatment. My Elmar 5cm lens when focussed on infinity and set to f12.5 shows a depth of field extending from 20 feet, and my Elmar 3.5cm at f12.5 shows the depth of field extending from just under 3 metres.
In the absence of any definitive literature explaining the purpose of the infinity catch we can never be sure of course, but I think that this is its most likely primary purpose, and the other used ascribed to it are secondary spin offs.
Well it's been an interesting post trying to answer what I thought was a very simple question. I thank everyone who has made a positive contribution to it.
Regards - David
But here is a scan of a page from an instruction manual for a IIIc, which does give a lot more detail about deploying and changing lenses.
As can be seen the only mention of the focussing lever is when attaching a lens to a body, where it says that the lens should be presented so that the focussing lever is in front of the viewfinder window. It doesn't mention the infinity catch, but the supposition must be that it is engaged, or else the location of the focussing lever would not be relevant.
The text does not mention, and the pictures do not show, the focussing lever / infinity catch being used in either deploying the lens (drawing out and locking or unlocking and collapsing) or removing and attaching a lens. If one of these actions were the primary purpose of the infinity catch, I think it would be described clearly, but in fact the infinity catch is not mentioned at all. The text says to remove the lens one should "grasp the lens close to the camera body" i.e. on the fixed part of the mount, not the focussing ring.
The infinity catch is described in a separate section on the next page. Its action is clearly described, but not its purpose. From this description it seems clear that the writer of the manual knew how it worked but did not know the reason for the infinity lock. E.g. he doesn't say "This is used for ... " or "This is useful when ... ".
In several sources it is reported that Barnack was a keen walker and probably liked to take landscapes. Perhaps he placed the "hockey stick" infinity locks on the early Leicas so that he could lock the lens on infinity and then not worry about it being disturbed from that setting by his walking activities. With a reasonable combination of shutter speed and aperture selected he could then walk freely, and take pictures just by looking through the viewfinder and pressing the shutter without having to adjust any setting on the camera at all. Because the hyperfocal distance varies with aperture, and hyperfocal focussing isn't really vital for distant landscapes, he just made a sensible compromise and chose infinity as the setting.
When interchangeable lenses were introduced it was only the short 3.5cm and 5cm which were given the focussing lever and infinity catch, I believe, and these lenses are the ones with great depth of field and relative insensitivity to focus compared to long lenses, these are the lenses most amenable to this kind of set-and-forget treatment. My Elmar 5cm lens when focussed on infinity and set to f12.5 shows a depth of field extending from 20 feet, and my Elmar 3.5cm at f12.5 shows the depth of field extending from just under 3 metres.
In the absence of any definitive literature explaining the purpose of the infinity catch we can never be sure of course, but I think that this is its most likely primary purpose, and the other used ascribed to it are secondary spin offs.
Well it's been an interesting post trying to answer what I thought was a very simple question. I thank everyone who has made a positive contribution to it.
Regards - David
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t6un
Established
David, thanks for the manual. I actually agree with you that a design feature doesn't always need to have one definitive reason. We also have to take into account the overall technical culture at the time. Moving parts of machinery needed to be locked down while inactive to protect them from rattling around, people put the tools back where they took them from after use, and locked the drawers...
The users of Leica at the time probably came from using folders that were filled with all kinds of secret locks? At least not from DSLR's... Rack and pinion focusing systems often have a locking screw that can lock the focus at any point. It wasn't possible with the then new helicoid, but at least they provided one lockable position?
The infinity lock also reminds me of the once universal design feature of radios: volume control button integrated with on/off switch at the low end of the dial: a clever way to avoid turning the radio on and finding it being set to some unexpected volume level... Many people would hate having it on their ipod, I imagine.
The users of Leica at the time probably came from using folders that were filled with all kinds of secret locks? At least not from DSLR's... Rack and pinion focusing systems often have a locking screw that can lock the focus at any point. It wasn't possible with the then new helicoid, but at least they provided one lockable position?
The infinity lock also reminds me of the once universal design feature of radios: volume control button integrated with on/off switch at the low end of the dial: a clever way to avoid turning the radio on and finding it being set to some unexpected volume level... Many people would hate having it on their ipod, I imagine.
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ampguy
Veteran
During the war, materials for lens cases and camera cases were in short supply. The infinity lock ensured the lens was stored in it's most compact position, allowing less precious material to be used and a smaller camera case to be made.
_goodtimez
Well-known
Two of my four Super Angulon 21mm f3.4 have an infinity lock; they are chromed.
My two other black ones don't have it.
All four a strict M mount
rxmd
May contain traces of nut
Is this a joke?
BobYIL
Well-known
Before the ‘50s the lens barrels were manufactured by turning on lathes or automats, the outer surfaces were therefore mostly slippery. To mount a screw mount lens of 50mm or shorter FL, especially with the collapsible types, a tab, a small lever, i.e. some sort of protrusion was needed so that torque could be applied to firmly screw the lens down on the flange and to assure that it would not come loose during usage (not like the later M-mounts). The longer focal lengths like 90 and 135mm for instance, did not need such tabs as their barrels were long enough to allow firm grip with fingers. The best place to place this tab was the end of the clockwise course to screw down the lens but also the beginning of the counterclockwise course to unscrew the same lens. To locate it on the 7 o’clock position was rather ergonomics, to be “away” from the other functions of the camera.
Infinity position: Any lens is shortest in length at infinity but the focusing helicoids have the longest mesh on the majority of such lenses, so that during screwing and unscrewing the helicoids will not be stressed. This could be the reason engineers wanted to lock the barrel rather at the infinity mark.
The same tradition continued even after the ‘60s with some lenses like the 35mm Summaron, Summicron or Summilux, as the barrels of these lenses too were manufactured the same way. For any focusing tab later then these I presume they were to meet customer preferences rather than the manufacturing methods.
Infinity position: Any lens is shortest in length at infinity but the focusing helicoids have the longest mesh on the majority of such lenses, so that during screwing and unscrewing the helicoids will not be stressed. This could be the reason engineers wanted to lock the barrel rather at the infinity mark.
The same tradition continued even after the ‘60s with some lenses like the 35mm Summaron, Summicron or Summilux, as the barrels of these lenses too were manufactured the same way. For any focusing tab later then these I presume they were to meet customer preferences rather than the manufacturing methods.
Mr_Flibble
In Tabulas Argenteas Refero
In my opinion; compared to the infinity lock on the Contax II/Kiev II it's an absolute blessing.
David Hughes
David Hughes
Hi,
I said a while ago that I'd have a look through all my books. Well, I did and nothing came of it and then I wondered and started reading what I could find in the old books about the hyperfocal distance, etc. Mostly because I'd expected it to be mentioned more; in my old trade I was very interested in what wasn't said, it's often more important than what is said.
It gets mentioned here and there but there seem to be two ways of looking at it;
1, Example; focus on 5m at f/8 and everything from 3m to 15m will be in focus. And
2, Example; when focused on infinity at f/8 everything from 8m will be in focus.
So I guess that Oskar Barnack was a "when focused on infinity" photographer but these days we all prefer it the other way.
And then, last night, I found an old-ish book (1993) I'd forgotten and it confirmed that both methods are/were used. So that may well be your answer.
Regards, David
I said a while ago that I'd have a look through all my books. Well, I did and nothing came of it and then I wondered and started reading what I could find in the old books about the hyperfocal distance, etc. Mostly because I'd expected it to be mentioned more; in my old trade I was very interested in what wasn't said, it's often more important than what is said.
It gets mentioned here and there but there seem to be two ways of looking at it;
1, Example; focus on 5m at f/8 and everything from 3m to 15m will be in focus. And
2, Example; when focused on infinity at f/8 everything from 8m will be in focus.
So I guess that Oskar Barnack was a "when focused on infinity" photographer but these days we all prefer it the other way.
And then, last night, I found an old-ish book (1993) I'd forgotten and it confirmed that both methods are/were used. So that may well be your answer.
Regards, David
Dralowid
Michael
I really don't know what this is all about.
The infinty lock just IS.
It is not there to be questioned or queried.
At the dawn of time Wetzlar so decided. Thus it is decreed till the end of time.
End of conversation
The infinty lock just IS.
It is not there to be questioned or queried.
At the dawn of time Wetzlar so decided. Thus it is decreed till the end of time.
End of conversation
David Hughes
David Hughes
Ah! I wondered what that bit in Leviticus meant. It's all clear now...
Regards, David
Regards, David
David Hughes
David Hughes
Reality...
Reality...
I was using the M2 with the collapsible Elmar F/2.8 50mm lens on holiday and it is very difficult to set the aperture after focusing as the thing will twist round and out of focus. So I soon realised that the aperture should be set when the thing is locked at infinity and then focussed.
I hope this answers the question even though the 50's Elmar is not quite like the 30's Elmar.
Regards, David
Reality...
I was using the M2 with the collapsible Elmar F/2.8 50mm lens on holiday and it is very difficult to set the aperture after focusing as the thing will twist round and out of focus. So I soon realised that the aperture should be set when the thing is locked at infinity and then focussed.
I hope this answers the question even though the 50's Elmar is not quite like the 30's Elmar.
Regards, David