100 years Null-Serie

[Ambro51]

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That image is deceptive. The brighter ring is a raised shoulder

[willeica]

13 hours ago, Ambro51 said:

That image is deceptive. The brighter ring is a raised shoulder

Thanks, I will check my 42mm Summar. Helicoid focus was not common for cameras back then. 

William 

[Roland Zwiers]

Ambro51 (sorry that I don't know your personal name),

Thank you so much for your empirical observations on M875 and the Ur-Leica.

They deserve a more substantial reply.

You mention that the Ur-Leica accepts the 1:4,5 f=42mm Mikro Summar and in addition the 1:3,5 f=50 and f=64mm Kino Tessars. This is already very important information!

Could you explain which of these lenses fit M875?

Could you tell which of these lenses could be exchanged between M875 and Oskar Barnack 's movie camera?

Roland 

 

 

 

[Ambro51]

The 64mm would be the Leitz lens, I don’t have one personally I’m only speculating.  If the cell thread matches the 5cm Kino Tessar, the barrel is the correct length.    It seems that the inner diameter of the tube on M875 is just large enough for the Kino Tessar in its cell to slip in.  The thumbscrew on the tightens the lens in place.  I’d love to know Zeiss list price for that Kino Tessar in 1911.  I’ll be shooting more images with M875 soon.  The best film I’ve used has been ISO 6.   For faster film (TriX) I put on a red filter.  The ISO 6 film approximates the speed of the Cine film used. 

Edited October 23 by Ambro51

[Roland Zwiers]

14 minutes ago, Ambro51 said:

The 64mm would be the Leitz lens, I don’t have one personally I’m only speculating.  If the cell thread matches the 5cm Kino Tessar, the barrel is the correct length.    It seems that the inner diameter of the tube on M875 is just large enough for the Kino Tessar in its cell to slip in.  The thumbscrew on the tightens the lens in place.  I’d love to know Zeiss list price for that Kino Tessar in 1911.  I’ll be shooting more images with M875 soon.  The best film I’ve used has been ISO 6.   For faster film (TriX) I put on a red filter.  The ISO 6 film approximates the speed of the Cine film used. 

Ambro51,

Thank you for your reply.

Yes, the 64mm lens must be a Leitz lens, probably the 1:4,5 Mikro Summar. So in your empirical observations the Ur-Leica could be equipped with the 1:3,5 f=50mm Kino Tessar, and with the 1:4,5 f=42mm and f=64mm Mikro Summar. 

As you say, the 1:3,5 f=50mm Kino Tessar was designed for the 18x24mm format. So it would not cover the 24x38mm frame of the Ur-Leica. Oskar Barnack must have known this in advance. So it is important to empirically observe that he still combined this lens with the Ur-Leica! Very likely the useable image circle of the Kino Tessar was slightly bigger than 18x24mm, so Oskar Barnack may have wondered how big a negative frame was still possible.

Note that the 1:3,5 f=50mm Kino Tessar was introduced in 1907 while Oskar Barnack was employed at Zeiss Palmos. Around this time he combined this lens with a prototype 18x24mm Minigraph camera. According to a former colleague of Barnack at Zeiss Palmos inspired Barnack to double the negative frame of perforated 35mm cine negative film for photographic purposes.

I wonder how quickly one could change these three lenses on the Ur-Leica. Could this have been done in mid-flight, e.g. while on board a Zeppelin?

Note that the 1914 Zeppelin pictures imply the use of a colour sensitive black-and-white film (presumably self-sensitized) in combination with a yellow filter. Combining a yellow filter with the 1:4,5 Mikro Summar must have been complicated because of the rotating lens cover. Possibly the 1:3,5 Kino Tessar could more easily be combined with a push-on filter.

Note that in 1907, so while Oskar Barnack was employed at Zeiss Palmos, Zeiss also introduced a 1:4,5 f=55mm Tessar for the 4x4cm format of the French 4,5x10,7cm stereo camera's. This lens would have covered the full 24x38mm frame of the Ur-Leica at a higher quality than was possible with the 1:4,5 Mikro Summars. 

So here I wonder why Oskar Barnack acquired a 1:3,5 f=50mm Kino Tessar instead of the more suitable 1:4,5 f=55mm Tessar. 

The likely explanation is that he first wanted to experiment with cinematography. And that after his successful experiments with cinematography he considered photography with the same 35mm cine negative film. Much in line with his 1931 observations in Die Leica.

To be continued.

Roland 

 

[Roland Zwiers]

On helicoid focussing

Ambro51, William,

The Ur-Leica design is interesting for many reasons. We already discussed the option to choose between three lenses: the 1:3,5 f=50mm Kino Tessar, and the 1:4,5 f=42mm and F=64mm Mikro Summars.

Now all these three lenses had to make use of helicoid focussing with an accurate focussing scale so as to be useful for photography without an additional ground glass.

Suppose the three lenses made use of one and the same helicoid focussing mechanism. In that case Oskar Barnack already employed some system for accurately matching lenses of different focal lengths, much earlier than 1930-1931 as discussed by William in earlier contributions.

This would almost be too good to be true. So the alternative explanation is that Oskar Barnack experimented with adapter rings and/or interchangeable helicoid mechanisms so as to match the various lenses in use. This would have te be complemented by matching interchangeable viewfinders.

In each situation it was crucial that a helicoid system was calibrated with an accurate distance scale. So a reading at e.g. 3 meter on the scale should focus exactly at 3 meter. 

This requirement was not new. In the 1890s it was already patented (even in Britain!) by Ottomar Anschütz for what would become the Goerz AnGo press camera. This camera system became popular very quickly for press photography. It was widely copied, also by Zeiss Palmos after 1902. 

These AnGo type press cameras did have an additional focussing screen, but in practice this was not used in combination with the standard lens. It came in handy when wide-angle or telelenses were employed.

So when Oskar Barnack designed the Ur-Leica, he made use of the helicoid focussing system that had already been in use for some 15 or 20 years. The same solution was used on cameras that he had been producing himself for Zeiss Palmos (the 6x9 Film Palmos of 1900, the various Minimum Palmos cameras for plates, his own 9x18 Stereo Minimum Palmos).

For me the most exciting question is how Oskar Barnack interchanged the three available lenses for the Ur-Leica. Did he already use a 0-solution? Or did he use exchangeable helicoid mechanisms, two of which have gone lost?

To be continued.

Roland 

 

 

 

[Roland Zwiers]

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Helicoid focussing with the Ur-Leica (II)

On the Ur-Leica is one helicoid focussing mechanism.

Ambro51 shows that there may be facilities to combine the Ur-Leica with three different lenses:

- the 1:4,5 f=42mm Mikro Summar 

- the 1:4,5 f=64mm Mikro Summar 

- the 1:3,5 f=50mm Kino Tessar 

It is important to check whether or not I have understood this correctly.

If so, then in 1914 Oskar Barnack may have had three lenses at his disposal with three different focal lengths.

But the remaining Ur-Leica only has a helicoid focussing mechanism for the 1:4,5 f=42mm Mikro Summar. I infer this from Ulf Richter (2009).

The focussing scale on the Ur-Leica must be matched to this 1:4,5 f=42mm Mikro Summar.

Without matched focussing scales the other two lenses could only be useful for taking pictures at infinity, on condition that Oskar Barnack had made sure that these lenses could be positioned in their infinity position. The measurements provided by Ambro51 suggest that this may have been the case.

In this situation Oskar Barnack may have used the three lenses for his 1914 Zeppelin pictures even without additional focussing scales. The distance from the Zeppelin to the surface would easily have been more than 1000x the focal lengths of the lenses in use. So he could just have put the lenses in their infinity position without having to look at a focussing scale at all.

It is important to check if this additional step in my reasoning is plausible.

If so, then there is a remaining question. Did Oskar Barnack make additional focussing scales for the 1:3,5 f=50mm Kino Tessar and for the 1:4,5 f=64mm Mikro Summar? Have these gone lost?

Or did his 1914 experiments convince him to stick to the 1:4,5 f=42mm Mikro Summar? And so he never produced additional focussing scales for the other lenses?

Additional question:

When in 1914 Oskar Barnack spent so much time and effort on testing suitable lenses for his Ur-Leica, why did he not consider the available 1:4,5 f=55mm Tessar?

To be continued.

Roland 

 

 

 

 

 

 

[Roland Zwiers]

Helicoid focussing with one mechanism and lenses of different focal lenghts

The Ur-Leica configuration seems to have one helicoid focussing mechanism with one focussing scale.
This focussing scale is calibrated (accurate) for the 1:4,5 f=42mm Mikro Summar.
I infer this from Ulf Richter (2009).
I infer from Ambro51 that the Ur-Leica can also accomodate the 1:3,5 f=50mm Kino Tessar and the 1:4,5 f=64mm Mikro Summar.

It is possible that I am already making interpretation errors at this stage.
If so, please tell me so.

When the same helocoid focussing mechanism is used for three different focal lengths, then the available focussing scale can not be accurate for two of the three lenses.
With the Ur-Leica I infer that this must be the case for the 1;3,5 Kino Tessar and for the 1:4,5 f=64mm Mikro Summar.
One exception can be the infinity mark on the focussing scale.
With compensating distance rings Oskar Barnack may have made sure that the additional lenses would still focus to infinity when the focussing scale was set at infinity as well.
It would be interesting to test this empirically with the Ur-Leica itself!

Now I have been looking in my collection for other cameras with a similar configuration.
One example is the Kodak Retina IIc with the interchangeable f=35mm, f=50mm and f=80mm lenses.
These three lenses make use of one and the same helicoid focussing mechanism as well.

So how is this possible?
One can observe that all three lenses are set at infinity when the helicoid focussing machanism is set at infinity.
On closer focussing the f=35mm and f=80mm lenses of the Retina diverge from the standard focussing scale that is calibrated for the 50mm lens.
But both the 35mm and the 80mm lenses have individual 'translation-scales', that show the photographer what distance on the 50mm scale corresponds with what distance for the 35mm and 80mm lenses.
 

A second intersting example is the VP Exakta of 1933 for 127-film (negatives of 4x6,5cm).
This SLR has one focussing mechanism with one focussing scale that is calibrated for the f=7,5cm standard lens.
[It even seems that the focussing scale is only accurate for the standard lens that originally accompanied the camera.
With three different f=7,5cm lenses the focussing scale gives different values when focussing at an object at 3m distance!]

With the VP Exakta it again seems that the infinity position on the focussing scale is accurate for lenses of different focal lengths. 
I tested this with a 1:6,8 f=5,6cm wide-angle lens and with a 1:5,5 f=150mm tele-lens.
Interestingly, the wide-angle and tele-lenses do not have separate focussing scales.
But in practise this does not matter since one focussus on the ground glass anyhow.

Without a focussing screen, the Ur-Leica depended on an accurately calibrated focussing scale on the helocid focussing mechanism.
This would also have applied with an accurate external rangefinder!
Otherwise the lenses in use could only be used in the infinity position. 

Note that these bottlenecks were not important for the Ur-Leica Zeppelin pictures of 1914.
On this flight Oskar Barnack may well have tested all three available lenses in the infinity position.

Note that for M875 the situation must have been different.
The opening at the back made it possible to look at the film plane.
Contemporary literature on cinematography makes clear that the film plane could be used as a ground glass for focussing.
Oskar Barnack may well have copied this feature for M875.

If so, then M875 may have used a long black leader (so as to protect the sensitive film), that subsequently switched to matte 35mm film (for focussing), and that would continue with several frames of unexposed 35mm film (for making the test exposures at 1/40 sec), before ending in another black leader (so as to protect the ecposed film).

To be continued.
If there is interest, I can provide pictures of the Retina IIc and VP Exakta configurations.

Roland