Rumoured Noctilux Family

[farnz]

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I didn't mean lazy as in lacking physical effort, just lazy thinking. I dare say there is someone out there who can take a great photograph of a fire hydrant or Ferrari badge at F0.95. I haven't seen one yet though, have you? 

 

Unfortunately that would draw us into the subjective realm of what constitutes a good/great/appealing/worthy/rubbish/boring/etc photograph so I'll leave it there.

 

Pete.

[NB23]

I seriously doubt a 90mm Noctilux in M-mount. But a "family" of the current 50mm plus 35 and 75 is possible - even likely, eventually. Especially remembering that Noctilux simply means "faster than f/1.4", not "faster than f/1.0".

 

F/1.2 lenses would qualify, as did the original 50mm Noctilux (f/1.2) or the already separately-rumored 75mm f/1.25.

Exact

[semi-ambivalent]

Since it's a bit unwise to design, now, exclusively for the past M, Leica might be designing, now, for the future M. Nobody who needed the Visoflex refused to use it because it violated the sanctity of the Messsucher. What's the minimum number of pixels needed to determine contrast? Do those pixels need to be at the film plane?

[IkarusJohn]

I am not sure which circle of confusion was used for the graphs linked by wattsy in #51. Leica still uses 0.03mm - same as 90 years ago. For modern means - which allow much higher micro contrast for the lenses, much higher resolution of a sensor and pixel peeping on the monitor, 0.01mm should be the maximum.

 

Edit: A posting worth to read from the age when rumors were less important:

https://www.l-camera-forum.com/topic/64993-depth-of-field-of-the-new-noctilux-f95/?p=680742

Arguably, circle of confusion is really only relevant to depth of field calculation, whereas rangefinder accuracy is an absolute. If the lens is accurately focused, then the plane of best focus will be the same, regardless of circle of confusion and resulting depth of field. One thing I wondered is if adding a magnifier affects the rangefinder accuracy shown on the chart? I would guess not. Similarly, I would guess that the new rangefinder in the M-A and subsequently in the M10 would give different results.

Edited November 7, 2017 by IkarusJohn

[pop]

Arguably, circle of confusion is really only relevant to depth of field calculation, whereas rangefinder accuracy is an absolute. If the lens is accurately focused, then the plane of best focus will be the same, regardless of circle of confusion and resulting depth of field. One thing I wondered is if adding a magnifier affects the rangefinder accuracy shown on the chart? I would guess not. Similarly, I would guess that the new rangefinder in the M-A and subsequently in the M10 would give different results.

Your visual acuity determines the accuracy of the rangefinder. Hence, the concept of the "circle of confusion", i.e. the largest disk you can not tell from a point, applies here as well. It is factored into the variable which expresses your visual acuity.

 

Adding a magnifier certainly affects the rangefinder accuracy. Rangefinders with different magnification factors differ in accuracy for this very reason. Adding a magnifier increases your virtual visual acuity by increasing the apparent size of everything you see in the finder.

[Jeff S]

Magnifiers can also exacerbate eyesight issues (and might reduce contrast), which is why it's important to correct for any problems (including astigmatism) before even thinking about a magnifier. Often that eliminates the need.

 

Jeff

[IkarusJohn]

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Your visual acuity determines the accuracy of the rangefinder. Hence, the concept of the "circle of confusion", i.e. the largest disk you can not tell from a point, applies here as well. It is factored into the variable which expresses your visual acuity.

 

Adding a magnifier certainly affects the rangefinder accuracy. Rangefinders with different magnification factors differ in accuracy for this very reason. Adding a magnifier increases your virtual visual acuity by increasing the apparent size of everything you see in the finder.

 

 

Interesting point.  I've always thought of circle of confusion as being a concept of resolution of sensors.  If we apply the concept of circle of confusion to visual acuity, then the graph would be as relevant today as it was 90 years ago, save for the improvement in rangefinder performance, first with the M(240) series of cameras and the M-A, and then the M10.

 

Presumably the improvements in the rangefinder could make a 75 Noctilux viable and might make a 90 Summilux also viable?  I ask purely out of curiosity - the 75 Summilux has a barely manageable dept of field wide open - I'm not sure I would have a use for either a 75 or 90 Noctilux.

[UliWer]

....

 

Presumably the improvements in the rangefinder could make a 75 Noctilux viable and might make a 90 Summilux also viable?  I ask purely out of curiosity - the 75 Summilux has a barely manageable dept of field wide open - I'm not sure I would have a use for either a 75 or 90 Noctilux.

 

 

Larger magnification of a viewfinder might help of course. With an M3 you would have less problems with a 75mm Summilux - but you'll miss the frames for 75mm... and of course there are no frames for 35mm...

 

This leads to the basic question: are lenses with super-narrow DOF a good option for a rangefinder camera? The answer is yes - up to 50mm. An 0.95/35mm Noctilux would not cause much worries for the rangefinder - as long as it is properly adjusted. With 50mm it becomes difficult but not impossible.

 

Anything longer with a minimal DOF puts too much stress on the rangefinder - and on the eye which looks though it.  People who get excited about some Noctilux rumors forget some facts which can easily be found:

 

At a distance of 2m which lens has the smaller depth of focus - according to the sheets published by Leica - : the 0.95/50mm Noctilux or the 2/90 Summicron Apo. Asph.?

 

Everybody can look up the sheets published on the Leica page: for the Noctilux they say for 2m at f 0.95: 1.957 - 2.045m. For the Summicron the say at 2 m at f 2: 1.970 - 2.031. Which one is smaller?

 

Anybody who wishes a 90mm with larger opening than f 1:2 wants to handle a DOF much, much narrower than for a 0.95/50mm Noctilux. Good look. 

 

For 75mm I don't find any sheets about the DOF of a lens with f 1:1.4 - but one can do some estimates: at f 2 and 2m the DOF of the 75mm Summicron is 1.956 - 2.047m. A little bit - 3 mm - wider than for the 50mm Noctilux at f 0.95 and 2 m. Now try to imagine f 1.25 at 75mm - I know there are a lot of eagle eyes around and only mine are insufficient.

 

Though there is focus peaking - isn't it? Yes: extremely narrow DOF is the the realm of focus peaking with the "Visoflex (Typ 020)" or even better with the display. I use it a lot with the Apo-Macro Elmarit-R 1:2.8/100mm. In very close distances - and with the ELPRO - the DOF is much smaller than the most extreme narrow ranges you get with any M lens  in normal distances - but focus peaking shows me exactly where the focus is, when my eyes could only guess and would fail.

 

So if Leica really offered the much rumored "Noctilux" for 75mm - they would make a statement: forget the rangefinder and use EVF. 

 

So why are there no rumors about a "Noctilux family" for the SL - much better EVF etc...?  They only announced a boring f1:2/75mm or 90mm (with equal or smaller DOFs than with a 50mm Noctilux). Perhaps they realize that SL-customers aren't as "tolerant" to prices as M customers?

 

A 75mm Noctilux (at f 1.25 or something) would be a statement by Leica: we are only interested in our customers spending huge sums of money. We are not interested in the usabilty of our lenses. 

[IkarusJohn]

...

For 75mm I don't find any sheets about the DOF of a lens with f 1:1.4 - but one can do some estimates: at f 2 and 2m the DOF of the 75mm Summicron is 1.956 - 2.047m. A little bit - 3 mm - wider than for the 50mm Noctilux at f 0.95 and 2 m. Now try to imagine f 1.25 at 75mm - I know there are a lot of eagle eyes around and only mine are insufficient.

... 

 

 

Using a depth of field calculator (True Depth of Field), with a circle of confusion of 12microns, focused wide open at 2 metres, the depth of field for the 75 Summilux is 2mm - 1.99 in front and 2.01 behind.  For the Noctilux at f/1 (my calculator doesn't go down to 0.95) all else equal, 4mm - 1.98 in front and 2.02 behind. 

Edited November 7, 2017 by IkarusJohn

[pop]

Interesting point.  I've always thought of circle of confusion as being a concept of resolution of sensors.  If we apply the concept of circle of confusion to visual acuity, then the graph would be as relevant today as it was 90 years ago, save for the improvement in rangefinder performance, first with the M(240) series of cameras and the M-A, and then the M10.

 

Presumably the improvements in the rangefinder could make a 75 Noctilux viable and might make a 90 Summilux also viable?  I ask purely out of curiosity - the 75 Summilux has a barely manageable dept of field wide open - I'm not sure I would have a use for either a 75 or 90 Noctilux.

The first application for the circle of confusion was for the quantification of your visual acuity. The old DOF charts and the DOF scales engraved on the lens barrels referred to this application: how large can a disc appear on a print for you to still accept it as a sharply depicted point.

 

In any discussion about rangefinder in cameras the visual acuity will appear at both ends of the complete process chain.

 

At the beginning it delimits the accuracy with which you can focus your lens. Statistically speaking, in a large number of shots taken at a particular distance with the same lens the actual focus distances will be scattered about the optimal distance, with the mean hopefully being the exact distance. The spread of the scattered distances will be determined by your visual acuity, of course. This is what the "accuracy" of the range finder really means. 

 

At the other end of the chain, you will look at a print of your photograph. The magnification of the print, the viewing distance and - again - your visual acuity will determine whether you will perceive some points which are not quite in focus as discs or as points.

 

Please excuse the stilted expression. That domain is not part of my active vocabulary.

[IkarusJohn]

The first application for the circle of confusion was for the quantification of your visual acuity. The old DOF charts and the DOF scales engraved on the lens barrels referred to this application: how large can a disc appear on a print for you to still accept it as a sharply depicted point.

 

In any discussion about rangefinder in cameras the visual acuity will appear at both ends of the complete process chain.

 

At the beginning it delimits the accuracy with which you can focus your lens. Statistically speaking, in a large number of shots taken at a particular distance with the same lens the actual focus distances will be scattered about the optimal distance, with the mean hopefully being the exact distance. The spread of the scattered distances will be determined by your visual acuity, of course. This is what the "accuracy" of the range finder really means. 

 

At the other end of the chain, you will look at a print of your photograph. The magnification of the print, the viewing distance and - again - your visual acuity will determine whether you will perceive some points which are not quite in focus as discs or as points.

 

Please excuse the stilted expression. That domain is not part of my active vocabulary.

 

 

No, I understand, thank you Phillip.

 

The point I was overlooking is the use of "circle of confusion" when it comes to optically aligning a parallax image.  If you can discern the two lines, and then get them aligned, you have (hopefully) achieved the best plane of focus, regardless of the lens or depth of field.  I hadn't thought of "circle of confusion" in that context.  As the image in the viewfinder is static, and unrelated to the aperture, focal length or resolving power of the lens or sensor and viewing distance, the concept of circle of confusion seemed irrelevant.

 

With the upgrading of the rangefinder, Ian's charts would seem to need modification, unless you're saying that our physical ability to detect alignment of the image in unaffected by the improved rangefinder.

[Reciprocity]

A 90mm Noctilux for the M is a great idea.

 

Since the rangefinder won't be usable to focus it, it makes sense to block the viewfinder by the lenses diameter.-

 

 

I bet my 105mm 1.4E on my Nikon D850 at ISO 12800 would bury the 90mm F1.0 on the M10 at ISO 6,400. 

 

I think the 35mm 1.4 FLE is about as big as I would ever want an M mount lens to be, otherwise what the heck is the point of that nice compact camera with huge lens on it? 

 

I hope they don't waste their R&D on this Nocti-bucks stuff, beyond the 50mm .95 it is just silly. 

[michaelwj]

Apologies if I'm off base, but I thought the only circle of confusion in Ian's chart is related the ability to discern correct alignment in the RF patch (under ideal conditions). The other half of the calculation for the chart (in focus or not) in my view would assume perfect theoretical mechanical focus (i.e. independent of film vs megapixels).

So from my reading the chart values are fixed and shouldn't change for film or digital or tighter mechanical tolerances (there is no tolerance in a theoretically perfect mechanical system). They are fixed values based on visual acuity. Tighter mechanical tolerances and a clearer RF patch would just bring you closer to the theoretical limit.

All this is largely irrelevant though, a 90mm Noctilux (<f/1.4) would most likely block the RF patch anyway. (Not necessarily the VF, but the smaller RF window). For example; A 1.2/90mm would require a 75mm diameter entrance pupil, which means the front element needs to be at least this big, compared to 65mm for the rumoured 1.25/75mm. For reference the 1.4/75mm needs a 53.6mm entrance pupil, and the 0.95/50mm would need a 52.6mm entrance pupil. Both have a 60mm filter. Of course, once the focal length is smaller than "normal" (lets call it the diagonal of the sensor ~ 43mm) other considerations determine the size of the front element, so a 0.95/35mm might not be possible either at the quality you want.

Sorry for the ramble.

[UliWer]

....

At the beginning it delimits the accuracy with which you can focus your lens. Statistically speaking, in a large number of shots taken at a particular distance with the same lens the actual focus distances will be scattered about the optimal distance, with the mean hopefully being the exact distance. The spread of the scattered distances will be determined by your visual acuity, of course. This is what the "accuracy" of the range finder really means. 

 

...

 

To avoid the scattered results you can hope that the DOF of your lens will hide the inaccuracies of your eyes - or the insufficiency of the rangefinder. That's the reason why Leica suggests to use the 1:3.4/135mm Apo-Telyt stopped down to f 5.6.

 

Though there is another factor working against this approach: the microcontrast of the lens. With a modern lens of the Leica brand - and especially longer focal lengthes - you expect very high microcontrast and they deliver it. Your approach towards the circle of confusion which one would accept as appearing to be sharp as a point becomes much more critical. Even a very tiny "extension" of the point towards a circle is regarded as unsharp - only due to the fact that the lens can deliver much better results and you see the differences because the microcontrast is so high. 

 

If you use a 1:1.9/73 Hector or even a 1:1.5/85mm Summarex you have the same narrow calculated DOF as for a modern lens. But those old lenses fully opened have a rather low (Summarex) or very low (Hektor) microcontrast. The difference between exact sharpness and slight unsharpness is much lower than with a modern lens, just because the maximum microcontrast of the lens is much lower. Your approach to the difference between sharp and unsharp is much more tolerant: there is a broad range where the result seems to be somewhat sharp even when the focus is not at the exact point, because no result from these lenses is really sharp if you apply modern standards of microcontrast. The large circle of confusion  of 0.03mm which was the base of the DOF-scales on lenses 90 years ago is not too big for a lens with low microcontrast. 

 

Now we are used to completely different results. The 75mm Summilux is a lens design more than 40 years old. Would we accept this today or would we demand more - a 75mm Noctilux with the same or even better microcontrast wide open as the Summicron? The 50mm Noctilux achieved this - it has its price. If a lens design with much larger opening allowed a very high microntrast - horribly difficult to achieve, but it is the Leica standard - the tolerance for sharpness would be much lower than for the older designs. Only a much smaller circle of confusion - less than 0.001mm - would be up to the modern standards. But then the demand to focus exactly becomes much higher. Those calculations which give you a tolerance of 2mm DOF for 2m won't be acceptable any more. 

 

Modern Leica lens design limits the possibility of very large openings for longer focal lengthes - it may be possible technically, but it won't be possible to use it. 

[michaelwj]

 

All this is largely irrelevant though, a 90mm Noctilux (<f/1.4) would most likely block the RF patch anyway. (Not necessarily the VF, but the smaller RF window). For example; A 1.2/90mm would require a 75mm diameter entrance pupil, which means the front element needs to be at least this big, compared to 65mm for the rumoured 1.25/75mm. For reference the 1.4/75mm needs a 53.6mm entrance pupil, and the 0.95/50mm would need a 52.6mm entrance pupil. Both have a 60mm filter. Of course, once the focal length is smaller than "normal" (lets call it the diagonal of the sensor ~ 43mm) other considerations determine the size of the front element, so a 0.95/35mm might not be possible either at the quality you want.

Sorry for the ramble.

 

 

Some quick measurements from a film M;

The RF window starts to be blocked with a lens with a diameter of 83mm and becomes completely blocked with a lens diameter of 99mm. (The RF patch in the main VF appears to be at the same distances)

The illumination window becomes completely obscured with a lens diameter of 86mm (not an issue on modern digital M bodies I know).

 

So, with a front element of at least 65mm for the 1.25/75 (and a 1.4/90 actually), this leaves no more than 9mm amount that element for the body/hood etc to not impact the RF window. A 67mm filter would be unlikely, so they'd have to step up to a 72mm filter, and we now have only 5.5mm to spare. Not much, but probably just manageable - the hood would need cutouts on both sides. 

 

Anyway, some food for thought.

[pop]

....

With the upgrading of the rangefinder, Ian's charts would seem to need modification, unless you're saying that our physical ability to detect alignment of the image in unaffected by the improved rangefinder.

First of all, the text introducing the chart is not entirely correct. The chart does not actually show the performance of the rangefinder device but the performance of an average human operating the device. That distinction is not usually relevant or useful, but it is so in the context of what we're discussing here.

 

The literature usually names three factors which determine the accuracy of a rangfinder, if I recall that correctly: the width of the base, the magnification of the rangefinder and the visual acuity of the user, all other factors being equal. The width of the base is given for the M type camera. The magnification is variable and the chart mentioned above gives advice for choosing a useful magnification. The visual acuity of the user varies with each user and with time, of course, and the chart has to be based on an average value for a person seeing reasonably well. YMMV, of course.

 

Ceteris paribus does not seem to apply any more for all M type cameras. With the intruduction of the M (Typ 240) Leica improved the performance of the system consisting of human plus rangefinder. I think they did it by increasing the optical contrast of the device, thus "improving" my visual acuity. The difference was dramatic in my case as I suddenly became able to focus the 135mm Elmarit-M reasonably well with the M, something I never could do on the M9.

 

So, yes, you could revise the chart for the M and the M10 by lowering the dashed lines. OTOH you could maintain that the new improved finders raised the age at which you could use a finder with the same magnification.

[pop]

To avoid the scattered results you can hope that the DOF of your lens will hide the inaccuracies of your eyes - or the insufficiency of the rangefinder. That's the reason why Leica suggests to use the 1:3.4/135mm Apo-Telyt stopped down to f 5.6.....

To be quite exact, you don't avoid the scattering of the results. What you do, and this is of course perfectly useful, is raising the tolerance of the imaging process. In other words: the scattering does not matter so much when you increase the DOF of the lens, unless you start magnifying the printed image at larger scales which then counteracts the improved tolerance.

[rramesh]

Gym! Got to go to the gym!

[adan]

Has anyone ever counted the number of threads here that eventually devolve into DoF threads? What is the fascination?

 

Me - I set the aperture according to the light available and the required shutter speed for camera/subject movement, focus on what is important - and the rest of the frame can go hang for all I care.

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Hallo,

Look here: Leica M

[Exodies]

It’s prolly because phone cameras can’t do shallow (until now).