Improved Digital Rangefinder for the M?

[lars_bergquist]

Advertisement (gone after registration)

There have been few posters here that have actually responded to the basic questions I addressed early in this thread (http://www.l-camera-forum.com/leica-forum/customer-forum/243938-improved-digital-rangefinder-m-2.html). Instead, there has been quite a lot of hand-waving by people who blithely accept the inaccuracies inherent in any AF system implemented in a non-reflex optical finder – for an AF system it would be, even though the final actuation would be done by a human brain and human fingers, instead of a processor and an electric motor. This disregard of accuracy is funny considering that it has been shown also by people who find the minuscule shift ot the focus plane caused by re-composing the image made by a wide angle lens utterly horrible.

 

This however is how we humans work: We are thrown into a panic by dangers we think we understand but disregard those that are beyond our willingness to learn and think about – even if those we imagine we know are minuscule or even unreal, while those we refuse to think about are great, and real.

 

But I think that the Leica people fully understand those issues. Leica is a small company that can ill afford any major miscalculation. So if a future M camera has some kind of focus confirmation it will probably apply only to an accessory 'Visoflex IV' electronic finder, not to the optical finder. As I pointed out in my original posting, acceptance of live view and of an EVF option would solve some of the problems and maybe alleviate the others so that their residue would be acceptable.

 

And that seems to be the majority view – amongst those who are able and willing to think the matter through. After all, a Leica is a practical tool, not a quasi-religious embodiment of the Absolute.

 

The old man from the Age of Tape Focusing

[Advertisement]

The Leica Q3 is available for pre-order at B&H Photo Video and Adorama

[pico]

Lars, I always look forward to your contributions for their technical insight, ages of wisdom, and even your comments of the curmudgeon. I'm not much younger than you in years, but haven't the engineering experience you have.

 

In my original post I was trying to address a new kind of rangefinder confirmation that kept current M lenses. It was proposed to provoke better ideas than I had, and you responded. Thank you.

 

One motive that I've had for many years was gifted to me by an uncle who made groundbreaking inventions and who told me at a young age, "When the answer is found, it will be simple." In fact, one of his patented inventions was hugely criticized with protests such as "That's too simple to be patentable! So obvious!" and he responded, "If it is so obvious, then why had it not been invented when humankind had the technology, and motive, for 3000 years?" (He actually believed that we do not invent, but instead discover. He and I are Platonists.)

 

--

Pico - happy with Leica M "as is".

[lars_bergquist]

Thanks, Pico. But my engineering experience is nil. I just have an irritating and perverse drive to find out about things and to think them through to the end. This, I have slowly learned the hard way, is not typical Homo sapiens behaviour, and it is distinctly impopular. You can see the resulting mess that H. sap. has made of the ongoing economic crisis.

 

Also, far from being a Platonist, I am an ontological (and hence epistemological) materialist curmudgeon. Einstein discovered the curvature of space, because it had existed all along, but Barnack invented the Leica shutter, because it had never existed before. And (please do not take this personally) in my previous posting I struck out the word 'Platonic' and inserted 'quasi-religious'.

 

The old man who can afford to stick his neck out

[pico]

[...]Also, far from being a Platonist, I am an ontological (and hence epistemological) materialist curmudgeon. Einstein discovered the curvature of space, because it had existed all along, but Barnack invented the Leica shutter, because it had never existed before. And (please do not take this personally) in my previous posting I struck out the word 'Platonic' and inserted 'quasi-religious'.

 

Sir Roger Penrose, a mathematics and physics genius, was a strong influence upon my learning and views. It just happens that he is also a Platonist by his own written admission. It was some years after his primary influence that I discovered that. He may have reshaped his view since his earlier statement. I don't know. BTW - Platonists are not necessarily religious, nor even quasi-religious.

 

Barnak did not invent the FP shutter and the earliest drop shutter's analogy can probably be derived from natural phenomena that can lead an insightful individual to consider the concept. That's a sign of Platonism.

[lars_bergquist]

There were of course focal plane shutters before Barnack. But they worked on a completely different principle. They had two curtains travelling in tandem, mechanically coupled to each others like waggons in a train. Shutter 'speed' (i.e. exposure duration) was actually regulated primarily by changing the tension of the springs that drove the curtains. This is why in English, alone of all languages I know, exposure times are still referred to as 'speeds' – but they are still measured not in feet per second, but in fractions of a second. This is of course absurd. "How fast did you travel on the motorway?" – "At about 1/250th of a second."

 

This regulation was insufficient, so you could also change the slit width. In Barnack's day most FP cameras had a table which told you which combination of spring tension and slit width produced (hopefully, approximately) which exposure duration, though shutters governed by one single dial existed after World War I. – These shutters by the way did in nearly all cases run vertically, along the short edge of the glass plate.

 

Barnack's invention was twofold. First, he used two mechanically non-coupled curtains, where the movement of the first curtain triggered the release of the second by means of an adjustable cam. The travel time and speed of the shutter curtains was now constant, it was the release delay that was adjusted. After the demise of the large format press camera, all FP shutters embraced this principle, i.e. they became Barnack shutters. This is true even for the Seiko shutter in the M, which has two sets of freely moving blades, travelling at constant speed and governed by varying the delay between the sets. Second, by making the curtains travel along the long edge of the film aperture, he could couple the re-tensioning of the shutter with the film transport.

 

Oskar Barnack was of course a mechanical genius. After his invention of the Barnack shutter, this was the obvious way of doing things, to the degree that Barnack's contribution was forgotten. But the curse of the Contax shutter was that it attempted to transplant the mechanical principle of the vertically travelling, mechanically coupled press camera shutter – the shutter the 'pros' used – to a 35mm camera. But they had to introduce mechanical compensations for the acceleration of the curtain arrrangement, which decreased the exposure towards the side they travelled to, while the Barnack shutter was self-regulating. So the Contax never had a really dependable shutter.

 

Now don't tell me that the Barnack shutter resided in some kind of empyrean 'sphere of ideas' before 1925, since the beginning of time. Ideas reside inside the skulls of people, because this is where they arise. What mathematicians think in these matters interests me not; they, and most theoretical physicists, are among the most philosophically naïve and superstitious people I know about. In their case, it is one of childish self-glorification – "see, I know a Great Secret!"

 

The old curmudgeon

[pico]

There were of course focal plane shutters before Barnack. But they worked on a completely different principle.

 

Uh huh. Barnak's first shutter was not self-capping. Self capping FP shutters preceded Barnak's later design. The fact that he made the variable traveling slit was not new, either.

 

[...[What mathematicians think in these matters interests me not; they, and most theoretical physicists, are among the most philosophically naïve and superstitious people I know about. In their case, it is one of childish self-glorification – "see, I know a Great Secret!"

 

Nonsense. Penrose discovered some very useful mathematical principles. Useful. Get it? Not just purely theoretical, but practical. Solving the tiling problem was monumental, even though it may be applicable beyond your particular horizon of interest or capability.

[giordano]

Advertisement (gone after registration)

I've not been close to enough mathematicians and physicists to form an opinion on the depths of their naivety and superstition, but apart from that I agree with Lars.

 

One small quibble: the second curtain of the traditional Barnack shutter is released not after a set delay, but after a set angle of rotation of the main shaft (which carries the drums from which the tapes of the first curtain are unwinding). If the shutter is in good order there's a consistent relationship between angle and time and the distinction is not important. It's only with the longer exposure times (and of course electronic shutters) that there's an explicit delay mechanism.

[pico]

I've not been close to enough mathematicians and physicists to form an opinion on the depths of their naivety and superstition, but apart from that I agree with Lars.

 

If you don't know, then your opinion is just that. FWIW I know many physicists and mathematicians and they do not participate in scientism. You might want to Google that word. Lars' hard-core materialist view is close to scientism.

 

Thanks for the pointer on the Leica shutter.

[giordano]

If you don't know, then your opinion is just that.

 

As I said, I don't even have an opinion. But I do know what scientism is.

[lars_bergquist]

Uh huh. Barnak's first shutter was not self-capping. Self capping FP shutters preceded Barnak's later design.

 

Yes, but I decided to pass that over, in the interest of brevity. Because these too were mechanically coupled designs, i.e. during the exposure, both curtains started simultaneously and travelled at the same speed – as I said, like waggons in a train. In the Barnack shutter, the first curtain started before the second; each had is own separate spring roller. And each had its own acceleration curve. That was the feature that equalized exposure across the film format. Sorry, I must not have made myself clear enough.

 

The fact that he made the variable traveling slit was not new, either.

 

Yes, I stated expressly that the slit width could be varied on early FP shutters. BUT – this width was mechanically set before the exposure, and remained the same during it, while the Barnack shutter increased the gap between the curtains during it, as the acceleration curve of the second curtain, while identical to that of the first, lagged behind it by a certain amount of time = exposure time. This compensated for the acceleration of the shutter.

 

As you was told, the work of genius does always have a certain simplicity or economy about it. Similarly, everybody expected before 1953 that the genetic code would be extremely complicated – too complicated even to be a 'code' proper. It turned out to have four 'letters' only … It was the genius of Crick and Watson to grasp that this simplicity still made nearly unlimited genetic variation possible.

 

Nonsense. Penrose discovered some very useful mathematical principles. Useful. Get it? Not just purely theoretical, but practical. Solving the tiling problem was monumental, even though it may be applicable beyond your particular horizon of interest or capability.

 

Mathematics is a language devised specially for statements about quantities. A mathematician (in Hilbert's time, though I don't think it was Hilbert) said that "God created only the integers. All the rest is Menschenwerk (human artifice)". Similarly, scientific theories are man-made models of limited aspects of reality. We accept them, provisionally, as long as they fit reality in some useful way. 'Mathemathical principles' that don't fit reality are scotched as 'wrong'; the reason why you would not trust a multiplication table that made two by two equal five, is not a theorem in numbers theory, but the fact that twice two nuts don't actually make five, when you count them.

 

And our mind is a Darwinian adaptation, evolved to help us dodge saber-toothed tigers and to run after dinners and mates. The fact that it can be used to some extent to make useable models of other aspects of reality is a bonus, as unexpected as unintended. The fact that we seem incapable of intuitively grasping both the wave and the quantum aspects of light simultaneously, is nothing remarkable. There was never any selection pressure in that direction before Einstein … Be grateful for what we can do, without constructing a Platonic world of Ideas, and then pining for it.

 

The epistemological curmudgeon

[lars_bergquist]

One small quibble: the second curtain of the traditional Barnack shutter is released not after a set delay, but after a set angle of rotation of the main shaft (which carries the drums from which the tapes of the first curtain are unwinding). If the shutter is in good order there's a consistent relationship between angle and time and the distinction is not important. It's only with the longer exposure times (and of course electronic shutters) that there's an explicit delay mechanism.

 

Perfectly correct. But logical nit-picking will always find a logical nit or two to pick. The hours hand on my old mechanical Omega does not move from one to two in one hour's time, but after a certain number of revolutions by the little wheels inside. Fortunately, the two quantities do coincide to some useful extent.

 

The old horological curmudgeon

[pico]

[... snip excellent explanation of Leica shutter ...]

 

Mathematics is a language devised specially for statements about quantities. A mathematician (in Hilbert's time, though I don't think it was Hilbert) said that "God created only the integers. All the rest is Menschenwerk (human artifice)".

 

Yes, I always like that expression. It was Kronecker, before Hilbert's time, but Hilbert proved one of Kronecker's theories. It is good linking them like that.

 

We simply disagree about the nature of mathematics. It can demonstrate things other than quantities, such as relationships. Look to advanced statistical and probability theories, for example. Very useful stuff.

[...]but the fact that twice two nuts don't actually make five, when you count them.

 

We call that Irish math. 2 + 2 = 10, presuming appropriate values of 2

And our mind is a Darwinian adaptation, evolved to help us dodge saber-toothed tigers and to run after dinners and mates. [...] Be grateful for what we can do, without constructing a Platonic world of Ideas, and then pining for it.

 

No pining on my part, and no construction can be done because it exists in toto or it does not exist at all.

 

--

Pico - e^(pi*i) = -1

[mjh]

A mathematician (in Hilbert's time, though I don't think it was Hilbert) said that "God created only the integers. All the rest is Menschenwerk (human artifice)".

That would have been Leopold Kronecker (1823–1891).

 

As a matter of fact I’m not even sure about the integers myself.

[lars_bergquist]

That would have been Leopold Kronecker (1823–1891).

 

As a matter of fact I’m not even sure about the integers myself.

 

Many thanks for Kronecker, both to you and to Pico. Old men forget. And I too think that Kronecker somewhat overestimated God's input – I think we invented the 'integer model' too, as a description of the fact that (with or without God's intervention) certain mass objects like nuts, stone axes and elephants come in discrete lumps, which have integrity over time and can be assembled into sets. But Kronecker's quip was certainly good literature.

 

I also remember Bohr's friendly ragging of Einstein during a discussion: "Albert, you talk altogether too much about God."

 

The unrepentant old unbeliever

[lars_bergquist]

We call that Irish math. 2 + 2 = 10, presuming appropriate values of 2.

 

This must be somewhat akin to the math taught in Swedish schools: "2 + 2 make more than two and less than twentytwo. The rest is a matter of negotiation."

 

The old arithmetical curmudgeon

[pico]

Many thanks for Kronecker, both to you and to Pico. Old men forget. And I too think that Kronecker somewhat overestimated God's input – I think we invented the 'integer model' too, as a description of the fact that (with or without God's intervention) certain mass objects like nuts, stone axes and elephants come in discrete lumps, which have integrity over time and can be assembled into sets.

 

Yes, it is difficult to imagine a world without the later inventions of the numbers 1 and 0. 1 was not necessary for counting when there was only 1 to count, and zero is just plain silly! Negative, imaginary numbers? Fugeddaboudit!

 

My favorite - a question to which the answer is literature, solve:

square root of 4b squared

 

The Bard knows.

[masjah]

Yes, it is difficult to imagine a world without the later inventions of the numbers 1 and 0. 1 was not necessary for counting when there was only 1 to count, and zero is just plain silly! Negative, imaginary numbers? Fugeddaboudit!

 

My favorite - a question to which the answer is literature, solve:

square root of 4b squared

 

The Bard knows.

 

Pico, presumably 4b^2 not (4b)^2? If so, then I know the answer, but I won't say in case others are still thinking aobut it!

[pico]

Pico, presumably 4b^2 not (4b)^2? If so, then I know the answer, but I won't say in case others are still thinking aobut it!

 

2B or not 2B

That is the question.

 

(Square roots are plus or minus)

[Advertisement]

Hallo,

Look here: Interesting Leica gear

[masjah]

2B or not 2B

That is the question.

 

(Square roots are plus or minus)

 

That's what I made it.

[SJP]

Ah.... so the question was ill posed it should have been 4.b^2, thus:

 

What is the sqrt of 4.b^2?

 

The answer (2b or -2b) has absolutely nothing to do with literature, it has to do with the way the world we live in works. People involved with literature I expect have better things to do, and likewise the scientists. "Gammas" economy, sociology & what have you ........

 

Anyway, whatever anyone may think, the underlying stuff is indeed eternal. Mathematics is not science, it is the mortar that holds the whole building together, if all other knowledge fails mathematics will remain true. Not that anyone really understands why, but that is a different issue.

 

Sorry for the rant, bad hair day (if available, it seems to be disappearing, probably a gene thing - will provide proof shortly but the available space in the margin is too limited here).