single frame lines

[bobbyk99]

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Is there a technical reason why Leica has the frame lines in pairs, rather than coming up alone in the viewfinder?

 

Scott

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[scott kirkpatrick]

If you'll accept a guess, it could be because there are many lenses to represent, and the lever that lets you preview the effect of using a different one has only three easily distinguished positions -- left, right and center. I don't have it with me at the moment, but I believe the M2 had only one frame in view at each position. The world has gotten more complicated since then.

 

scott

[karmadragon]

Cause more peoples prefer muti-views for muti-lens than a simple single view for just 3 or 4 lens. M2, M2S or M2R are only one frame for 35, 50 and 90mm lens. I think Leica can do it after the 6 bit code system by adding a electro-optical system( also the parallax correction needs a focusing confirmation system to move the frame lines).

 

Morgan

[elgenper]

[quote name=scott kirkpatrick... I believe the M2 had only one frame in view at each position. The world has gotten more complicated since then.

 

scott[/quote]

 

Sure, both M2 and M3 showed only one frame at a time; they only had three frames each.

 

And, in fact M2 is right when things DID get complicated: The M3 (first one) had 50, 90, and 135 frames in these three positions, and lenses were keyed accordingly to select the correct one. All other focal lengths used auxiliary finders. Simple and easy...

 

Only, when the M2 appeared a couple of years later, it had frames for 35, 50, and 90 in its three positions... and had to be able to use the existing, keyed 50 and 90 lenses, so these two positions remained where they were on the M3. But the 35 lenses now got the same keying as the existing 135 ones, in order to use that third position. Confusion, anyone?

 

Now, a period followed where different, "spectacled" lenses appeared, with "false" keyings, allowing an 135 on a M2 (and on a M3 too, for that matter) to use the 90 mm frame, but enlarge the image so a true 135 field-of-view resulted. Similar with 35´s intended for the M3, keying the 50 field and adapting it. (The dual-range Summicron 50 was another matter; these spectacles corrected for close focussing, not for focal length).

 

Later, people wanted 28 mm as well, and Leitz got the idea of showing two frames in each position (getting the 75 frame as a bonus). So 28 got to share the 90 position, and 75 the 50 one.... Phew!

[scott kirkpatrick]

Aha. Thanks for the history. That explains why we now have

 

24 + 35

28 + 90

50 + 75

 

which sounds like a funny set of pairings, but makes historic sense. Now I see why the Zeiss 25 owners are stuck trying to get a retrofit to its mount to make it look like a 35 mm lens. And the 135 which is no longer recommended would make the 24-35 frame lines come up?

 

scott

[bobbyk99]

I was reading the thread with "adan"'s decision to use the 28mm lens on his M8 because he finds the 24 and 35 frame lines too close:

 

"The 28 view is paired with a tiny, distant 90mm viewfinder. The 24 view is paired with very similar-sized 35mm framelines.

 

Everyone can make their own call - but I doubt I will ever use either a 24 or a 35 on the M8 with those confusing lines. 21 f/2.8, 28 f/2, 50 f/2 for me (plus a little something extra at each end)."

 

I guess making 6 effective positions on the preview lever so you have individual frame lines for 24, 28, 25, 50, 75 and 90 is impractical, or to use the lens coding to bring up single frame lines rather than pairs is impractical or unacceptable on some other level. I just thought it would solve that objection and some people, perhaps myself included, might find it preferable.

 

Scott

[adan]

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Bobby99: Thanks for the plug! 8^)

 

To extend Pers' history: In 1968 the M4 was introduced to replace BOTH the M2 and M3. To cover the 4 frames that those two cameras covered between them (35/50/90/135) with just the 3 frame setting positions designed into the system, the 35 and 135 frames are paired (which was a given anyway, since the M2 had 'borrowed' the 135 keying for the 35).

 

When Leica introduced the 75mm focal length around 1982, they had to find an additional spot for it in the 3-setting lineup. While they were at it, they decided to also squeeze in a 28mm frameline. The possible pairings (since 35/135 was already a given) were 28/50-75/90, or 28/90-50/75. I suspect they chose the latter because they figured more Leica users shot with 28s than would use the rather exotic, heavy and expensive 75, so they gave the "best" (i.e. least confusing, most widely separated) pairing to the 28. This was the M4-P camera.

 

The 21mm Elmarit lens (the only Leica-built M lens at the time wider than 28), also introduced about 1980, was given the same mount (and thus framelines) as the 28. Who know why? - although it may have been similar to Zeiss's reasoning with the 25mm - tag it to bring up the closest possible internal framelines.

 

Fortuitously (or with brilliant foresight), when the 24mm focal length was introduced in the mid-90's, it was distinguished from the 21 by matching it to the 35/135 mount. Along about that time, there were rumors of a "wide-angle" Leica with a viewfinder that would cover the superwides, and I guess Leica had in mind 21/28, 24/35, and 50/75 frame pairs (21/24/28, 35, 50/75 would have been REALLY confusing). Ultimately this only became the .58x body, with a better view of the 28 lines, but no new ones.

 

At this stage in the life of the Leica-M, it might be possible to re-engineer the mechanical frame-setting system to have 6 discrete settings - but half of 50 years of lenses would HAVE to have new mounts installed to fit that paradigm (as opposed to the "optional" zebra-coding) - i.e. either all 50s or all 75s would need remounting to split those frames.

 

And I'm not even sure it could be done - the two masks that a) contain the framelines and slide to cover and reveal them when lenses are mounted are about 1 x 1.5 cm, the actual cut-out lines are about .25mm wide and the movement of the mask from one frame set to the next is about 1mm. Even with just 3 settings, when the springs in the system start to age, one begins to see 'slop' in the system (part of two sets of lines show at once). To have 6 separate settings would require twice as much precision - 0.5mm of travel from one setting to the next - every time.

[carstenw]

With coded lenses, it would at least theoretically be possible now to use only one pair per lens, and still retain backwards compatibility via the old system. This would require computerizing the selection of frames, as well as a re-built rangefinder. Who knows if Leica will do such a thing in the future.

[scott kirkpatrick]

And, in fact M2 is right when things DID get complicated: The M3 (first one) had 50, 90, and 135 frames in these three positions, and lenses were keyed accordingly to select the correct one.

 

Only, when the M2 appeared a couple of years later, it had frames for 35, 50, and 90 in its three positions... and had to be able to use the existing, keyed 50 and 90 lenses, so these two positions remained where they were on the M3. But the 35 lenses now got the same keying as the existing 135 ones, in order to use that third position.

 

There is another little mechanical miracle going on in the M3-M2 transition. The preview lever on the M2 still uses the natural left = 35, center = 50, right = 90 ordering, even though the tab on the mount that presses sideways just a few mm away from the preview lever must, for consistency with the M3, use the conventions 50 = smallest radius, 90 = medium radius, and 35 = largest radius. In other words, the mount that pushes the lever to the left in the M2 and brings down the 35 mm viewframe would push the lever to the right in the M3 and bring down the 135 mm viewframe. Neat, huh?

 

scott