goggled v ungoggled 35mm lenses

[maximilianm3]

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hi there,

 

I have a question: does anybody know what exactly the differences are between the goggled 35mm lenses for the M3 and it's ungoggled versions apart from the obvious lack of goggles?

As far as i can work out the optical parts should be the same, but there seems to be a differences in thickness of the mount /helicoid/ focusing mechanism, the goggled ones being thicker and thus allowing for closer focus? Assuming that the optics are the same, focus at infinity should happen on both versions at the same distance of the sensor? As the goggled version allows for closer focus, am i right in assuming that the focusing mechanism must have a different gearing and or more throw (for lack of a better technical term)? 

Are the differences the same between the goggled/ungoggled Summaron, Summicron and Summilux lenses?  Are the goggles all optically the same?

 

Many thanks

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[a.noctilux]

You are right, the same optical cell and two focussing mechanism of "x1.6 rate".

Let's see with this (not so good) image from my post (2013 time flies so quickly)...

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Clever design from Leitz 😊.

My two 35mm Summaron "M3" at left and "M2 type" at right

we can see that the "ramping" is not the same, to

- allow focus to 65cm with 1meter moving equivalent when the "optical correction eyes" are in place

- transform the "optical corrected field of view" which key-in the 50mm frame to the 35mm "rate in focus movement"

- the lens "M3 type" with goggles or "M2 type" can be used with all Leica M

 

It is clever optical+mechanism melting pot to offer M3 RF Focus/framing those nice 35mm of that time: Summilux, Summicron, Summaron.

Summaron 3.5/35mm is another "M3 first type", not same "solution" as the faster siblings.

 

As side note: all the goggles are compatibles with "late 35mm M3 types",

I had swapped "to see if it can be done" SAMWO/11108  Summicron's goggles with Summaron's goggles (2.8 SIMWO/11106 ), it works fine swapped.

Edited October 10, 2019 by a.noctilux

[luigi bertolotti]

2 hours ago, maximilianm3 said:

hi there,

 

Are the differences the same between the goggled/ungoggled Summaron, Summicron and Summilux lenses?  Are the goggles all optically the same?

 

Many thanks

The other answers have been given in the previous mail; about those two : Summaron (3,5 and 2,8) Summicron and Summilux basically use the same principle of a different "ramp" of the helicoid , but the mechanical attachment of the goggle unit is different (in general, Leitz decided, after some years, to make the goggle unit not dismountable) ; also, the minimum focus distance of 0,65m (vs. 0,7m for the ungoggled lenses) was abandoned in due time… iirc, Summaron 2,8, Summicron and Summilux "switched" from 0,65 to 0,70 around s/n 1.900.000/2.000.000 (I don't know if it was a REAL reduction or just a modification of writing…the feet scale too was modified)  . Optically, I  think that all the 35mm goggles are identical (by logic) .

 As a side note, the goggle unit of the Tele Elmarit 135 is optically opposite (enlarges, instead of reducing, the image in the Viewfinder : the camera's 90mm frame encompasses a 135mm frame… on goggled 35s, the camera's 50mm frame encompasses   a 35 mm frame)

Edited October 10, 2019 by luigi bertolotti

[bayernfan]

would somebody be kind enough to explain to me why the goggled version of the 35/3.5 M-Mount has a shorter minimum focus distance than the non-goggled version?

what was Leitz's logic in producing a lens with a shorter focus distance strictly with the application of goggles?

 

[Michael Geschlecht]

Hello Bayernfan,

Welcome to the Forum.

The "goggled" version of the 35mm, F3.5, Summaron has a shorter focusing range of 1 meter to Infinity, As opposed to the 0.65 meters to Infinity of the other "goggled" 35mm lenses. Because it does NOT have the differential focusing mount of the lenses that focus to 0.65 meters.

Because the focus is Infinity to 1 meter, which is the focus limit (Generally) of most M3's: There is no necessity to have a fixed optical unit attached permanently to "goggles". The 35mm, F3.5 Summaron works the same with or without "goggles".  The other 35mm lenses, F2.8,  F2.0 &  F1.4 have differential focusing units that translates the Infinity to 1 meter movement of the M3 focusing roller into an Infinity to 0.65 meters of lens mount movement for those 3 lenses.

A movement ratio of 1 : 1.5  (Not 1 : 1.6).

That is to write: When the focusing mount is turned so that the roller on the camera (Any "M" model.) moves from Infinity to 1 meter: The lens mount moves the lens from Infinity to 0.65 meters.

More to come.

Best Regards,

Michael

Edited October 10, 2019 by Michael Geschlecht

[bayernfan]

10 minutes ago, Michael Geschlecht said:

The "goggled" version of the 35mm, F3.5, Summaron has a shorter focusing range of 1 meter to Infinity, As opposed to the 0.65 meters to Infinity of the other "goggled" 35mm lenses. Because it does NOT have the differential focusing mount of the lenses that focus to 0.65 meters.

0.65 m = 2' 1.6"

Here is my lens:

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[Michael Geschlecht]

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Hello Bayernfan,

I'm back.

With the 135mm, F2.8, Elmarit it is the same the other way around: The 1 : 1.5 ratio is the same as 90 : 135.

Here the Infinity to 1 meter movement of the focus roller gets translated by the focus cam from Infinity to 1.5 meters.

Now, instead of the "goggles" widening the view 50% the view is narrowed to 2/3rd's of what it is without the "goggles".

Nifty.

Best Regards,

Michael

Edited October 10, 2019 by Michael Geschlecht

[Michael Geschlecht]

Hello Bayernfan,

As per your Post #6, this Thread:

That is interesting. I misunderstood what you wrote.

I thought that you wrote that the 35mm, F3.5, Summaron with "goggles" that you have focuses from Infinity to 1 meter. Like the "ungoggled" 35mm, F3.5, Summaron.

Unlike the "goggled" F2.8, 2.0 & 1.4 versions which focus from Infinity to 0.65meters.

What you actually wrote appears to be: Why does the 35mm, F3.5, Summaron with "goggles" focus to 0.65 meters while the "ungoggled" version focuses to 1 meter?

The answer to why the"goggled" version focuses closer than the "ungoggled"  version is the same reason that it is for the F2.8, 2.0 & 1.4 versions.

Best Regards,

Michael

Edited October 11, 2019 by Michael Geschlecht

[bayernfan]

Thank you for the clarification Michael.  So my understanding is as follows:

The original M3 was only able to focus to 1m.  The goggled lens (with it's longer rotational movement (0.65m to inf)), uses a modified helicoid to shorten the VF cam movement to match the displacement of travel associated with a "regular"l Leitz lens.

Two questions still persist:

1. How does the the goggle magnification correct the VF distance alignment?

2.  Had the original M3 been able to focus to 0.65m, would a modified helicoid been necessary with goggled lenses?

 

Edited October 11, 2019 by bayernfan

[Michael Geschlecht]

Hello Bayernfan,

Your understanding of the differential movement of the focus barrel (1 : 1.5) to the focus cam & the focus roller (1 : 1) is correct.

For Question #2 the answer is: No. 

For Question #1 I don't understand what you mean by "distance alignment".

The purpose of the "goggles is to widen the field of view 1 : 1.5. Which is the same as from 45 degrees to 64 degrees (Approximately).

By the way, I am going to turn into a "Pumpkin" soon. You should keep writing.

I'll be back.

Best Regards,

Michael

Edited October 11, 2019 by Michael Geschlecht

[a5m]

I recently, reluctantly tried understanding how the whole goggle setup works and thought I had figured it out. I think I did, but this makes it very clear. Thanks to you all for explaining it so well.

[bayernfan]

2 hours ago, Michael Geschlecht said:

For Question #1 I don't understand what you mean by "distance alignment".

If I remove the goggles and use the viewfinder to focus, the distance indicated on the lens does not match the distance when the goggles are used.  

The goggles must in some way be correcting a distance scale discrepancy caused by the modified helicoid.  I suspect it is the goggle optics directly in front of the rangefinder window.  A change in magnification or perhaps something even more advanced...

Edited October 11, 2019 by bayernfan

[maximilianm3]

10 hours ago, Michael Geschlecht said:

Hello Bayernfan,

Welcome to the Forum.

The "goggled" version of the 35mm, F3.5, Summaron has a shorter focusing range of 1 meter to Infinity, As opposed to the 0.65 meters to Infinity of the other "goggled" 35mm lenses. Because it does NOT have the differential focusing mount of the lenses that focus to 0.65 meters.

Because the focus is Infinity to 1 meter, which is the focus limit (Generally) of most M3's: There is no necessity to have a fixed optical unit attached permanently to "goggles". The 35mm, F3.5 Summaron works the same with or without "goggles".  The other 35mm lenses, F2.8,  F2.0 &  F1.4 have differential focusing units that translates the Infinity to 1 meter movement of the M3 focusing roller into an Infinity to 0.65 meters of lens mount movement for those 3 lenses.

A movement ratio of 1 : 1.5  (Not 1 : 1.6).

That is to write: When the focusing mount is turned so that the roller on the camera (Any "M" model.) moves from Infinity to 1 meter: The lens mount moves the lens from Infinity to 0.65 meters.

More to come.

Best Regards,

Michael

Thanks for your answer, but i' find i a bit confusing.

My goggled Summaron 3.5 focuses to 0.65m like the one in the picture by bayernfan, so it seems that the focus mechanism between the goggled and ungoggled version has to be different.

My theory is that the rangefinder goggle tricks the rangefinder by altering the angle at which the subject to focus on gets to the prism and therefore allows to focus closer than normally possible with the rangefinder.

[maximilianm3]

9 hours ago, Michael Geschlecht said:

The answer to why the"goggled" version focuses closer than the "ungoggled"  version is the same reason that it is for the F2.8, 2.0 & 1.4 versions.

Best Regards,

Michael

Which is what since the rangefinder limitation is either 1 or 0.7m?

[a.noctilux]

My calculation in ratio was not correct,

the ratio must be 50:35 =1.428 or 35:50 = 0.7

As the optical correction ratio is to convert field of 50mm focal length to 35mm focal length,

it widens (or reduces) ratio of 0.7 the rangefinder (optical device) calibration must be corrected also,

the rate of focussing ramp (mechanic device) must be corrected in the same manner of 0.7 .

 

As I wrote in my former post, it's a clever optical + mechanical solution for a problem not seen before.

The close focussing to 0.65m is a secondary feature exploted by those clever Leitz engineers 😉

I don't know why 0.65m in place of 0.7m ( focus limitation of M3 to 1m transformed to ratio 35:50 in VF) ...another mystery to solve !

[bayernfan]

2 hours ago, maximilianm3 said:

My theory is that the rangefinder goggle tricks the rangefinder by altering the angle at which the subject to focus on gets to the prism and therefore allows to focus closer than normally possible with the rangefinder.

Yes. This is my theory as well.

I’d like to know the optical physics behind it. 

Edited October 11, 2019 by bayernfan

[Jul]

2 hours ago, a.noctilux said:

I don't know why 0.65m in place of 0.7m ( focus limitation of M3 to 1m transformed to ratio 35:50 in VF) ...another mystery to solve !

Well, at that time a lot of 50es were actually 51.9 (or 51.6 for some of them). Using 51.9 instead of 50 in your calculation would get you a little closer to 0.65  …

[bayernfan]

2 hours ago, a.noctilux said:

I don't know why 0.65m in place of 0.7m ( focus limitation of M3 to 1m transformed to ratio 35:50 in VF) ...another mystery to solve !

I suspect that the rangefinder goggle (which is modifying the rangefinder alignment angle) permitted slightly more focus range (down to 0.65m) than the ungoggled rangefinder mechanism (down to 0.7m)

Edited October 11, 2019 by bayernfan

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[Michael Geschlecht]

Hello Everybody,

There is no "tricking" going on here:

The M3 rangefinder measures from Infinity to 1 meter. With some exceptions not relevant to this discussion.

Which means that when a "goggled" lens focusing barrel is indicating that the focus point (Actual lens extension.) is at 0.65 meters:

The actual movement of the roller & the cam on the lens: Are at the point where they are measuring at an image plane at a distance of 1 meter.

The "goggles" widen the angle of view from that of a 50mm lens to that of a 35mm lens.

Best Regards,

Michael

Edited October 11, 2019 by Michael Geschlecht

[maximilianm3]

I would agree with you that at 0.65m focus on the lens the rangefinder thinks it's 1m. However this doesn't explain the trickery of the round goggle which definitely moves the rangefinder patch in the viewfinder vertically and horizontally when adjusted with the three little screws....  so what exactly is it's purpose if not to suggest that 1m is actually 0.65m?

I think the square goggle doesn't do anything to the fixed and movable rangefinderpatches.

 

 

Scratch that as you are right: all it does is reduce what is in the rangefinder patch from a 50mm view to a 35mm....

 

Edited October 11, 2019 by maximilianm3
My mistake