Speculations continuing?

[jaapv]

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Yes. And if you follow the link in that somewhat breathless report, you'll find that the resolution of the only organic sensor made to date is 360 × 256 (QVGA) and that Fuji says "research will continue"..... We will have to wait and see until real sensors come out and whether it will be more universal than for instance the Foveon technology which despite the promise appears to be a dead end; beautiful on paper, but quite limited in real life. At the moment the Exmor sensor is more of a reality, and even that one has not (yet??) made it to 24x36 size.

[jaapv]

If that is information and not misinformation Mirrorless Rumors | Blog | Will Fuji use a new organic sensor? Is that the key to beat fullframe sensors? this type of sensor would be very interesting for Leica lenses as it is supposed to work with "slanting rays of light" without any micro lenses. Sounds more like film - no retrofocus WA lens design is required. Smaller (and maybe cheaper) lenses like the Zeiss ZM Biogon 21mm/f4.5 could be used.

Leica can anyhow not rely on Kodak as a longterm supplier of sensors.

Virtually all modern WA lenses are retrofocus. And not because of sensor limitations, but because it gives more scope for correcting aberrations in faster lenses. It has taken lens designers a long time to master the technique, but there is not one that would want to take the step backwards to symmetrical designs.

[lct]

Interesting indeed. Thanks for sharing.

[giordano]

Virtually all modern WA lenses are retrofocus. And not because of sensor limitations, but because it gives more scope for correcting aberrations in faster lenses. It has taken lens designers a long time to master the technique, but there is not one that would want to take the step backwards to symmetrical designs.

 

I have the impression that the one area where retrofocus WA lenses are inherently superior is their relative freedom from of cos^4 vignetting, and that the greater scope for correcting aberrations is a matter of engineering practicality: the number and size of elements aren't constrained by the dimensions of the film chamber.

[mjh]

If that is information and not misinformation Mirrorless Rumors | Blog | Will Fuji use a new organic sensor? Is that the key to beat fullframe sensors? this type of sensor would be very interesting for Leica lenses as it is supposed to work with "slanting rays of light" without any micro lenses.

Of course such a sensor would be interesting – that’s why I’ve covered Fuji’s work on organic sensors in my overview of (then) current developments in LFI 2/2008. The real question is whether such a sensor will be ready for prime time in, say, next year. And we don’t know. Naturally, neither do we know how the sensor would actually perform, whether Fuji would market it to competitors etc. etc.. Right now and for all practical purposes, the organic sensor pretty much pie in the sky.

[Guest #12]

Virtually all modern WA lenses are retrofocus. And not because of sensor limitations, but because it gives more scope for correcting aberrations in faster lenses. It has taken lens designers a long time to master the technique, but there is not one that would want to take the step backwards to symmetrical designs.

 

 

I don't think there's anything inherently backwards about a symmetric design. What it does it does perfectly; retrofocus is a little ad hoc from the get go. Modern wide angle rf lenses in medium format are still symmetric designs. Cost and complexity is also a factor.

[jaapv]

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Just paraphrasing Erwin Puts...

[40mm f/2]

Virtually all modern WA lenses are retrofocus. And not because of sensor limitations, but because it gives more scope for correcting aberrations in faster lenses. It has taken lens designers a long time to master the technique, but there is not one that would want to take the step backwards to symmetrical designs.

 

The best WA lens I own is the Schneider Super Symmar 110mm XL. It is not symmetric but also no retrofocus! -and it also does not fit any Leica.:

[Guest #12]

Just paraphrasing Erwin Puts..

 

I have trouble finding anything in this book without an index, and haven't read it, but...

 

On the 1950's: "A wide-angle lens could be created with a symmetrical design, but with a small aperture." (p.395)

 

"The change to a retro-focus design for the Leica-M in the case of the 28mm, brought a slight performance drop at first."

 

"The gradual change from symmetrical to retrofocus types for the M-camera was necessary since the introduction of the M5. The second more disguised argument for the change to this newer type of designs is the higher optical potential. As soon as the designer has familiarized himself with the inherent characteristics of retro-focus designs, he has more opportunities for corrections." (p.399)

 

"...classical Double-Gauss formula. This design type, now more than a 100 years old, has been stretched to the limits and a performance plateau has been reached." (p. 422)

 

"Retrofocus designs are a second approach to step out of the shadows of the Double-Gauss formula. More lens elements can potentially improve performance, as more parameters can be controlled." (p. 422)

 

*****

I think from a proper source you will get the idea that both have their tradeoffs. I guess you are basically trading distortion and a big aperture for spherical aberration. If you are interested in something else besides a big aperture, maybe you will still be interested in a symmetric design. Both of these ideas have been around for about a 100 yrs., and not much gets thrown away in lens design. Fuji, Bronica, Mamiya all have modern symmetric wides...they are slower and cheaper, but arguably some of the best lenses in medium format and I don't think you would call them backwards because of the design choice.

[lct]

Does the choice between double Gauss and retrofocus play any role in the physical size of lenses? Just curious.

[jaapv]

The quote from page 399 was indeed the one I was thinking of.

[giordano]

Does the choice between double Gauss and retrofocus play any role in the physical size of lenses? Just curious.

 

Yes - but not necessarily by very much when you allow for the fact that modern retrofocus WA lenses are usually faster than their symmetrical predecessors.

 

For example, the old, double-Gauss 28/5.6 Summaron is far smaller than any recent Leica 28mm - but it's also between two and four stops slower.

 

On the other hand there's not nearly as much difference in size between the (basically symmetrical) 21/3.4 Super Angulon and the retrofocus 21/3.4 Super Elmar.

 

Also, of course, the degree of retrofocus has a big effect. Compare for example Leica's Summilux 24/1.4 with the Canon or Nikkor equivalents: the extra 20mm or so clearance required by the SLR mirror has forced the designers to use more and bigger elements.

[jaques]

does anyone think it is technically possible to make a camera with a finder like the X-100 but capable of accommodating an m mount and interchangeable lenses?

 

If it has the optical option then I suppose such a finder would have to be able to 'zoom' mechanically.

 

If so then that is my bet for one of Leica's upcoming cameras...

 

To create such a camera would it be totally farcical to suggest having a much larger finder altogether? (to accommodate the zooming abilities and extra tech)

 

certainly seems like a brilliant theoretical camera to me. Imagine shooting a 135- RF style- but zoomed in so that the frame is like the 50mm one? I guess such a finder would have to zoom- and adjust for parralax (the finder itself- not the frame-lines)- and perhaps that just is too much to ask... and mechanically overcomplex ;-)

 

The X-100 RF style optical finder is really great- a true innovation- the parallax compensation really is a marvel to watch. A little trick: set the camera to OVF mode-.... now set it to manual focus... Voila- optical finder can now be used for macro. I don't think this is even mentioned in the manual...

 

Use the little AF button to focus instead of the lens ring. Once focus is confirmed lightly press the shutter button- Watch that frame adjust for parallax! amazing... it can move right out of the finder almost... No Leica could ever do that... (of course it is bloody stupid to shoot macro this way- the EVF is far better).

 

I don't even think you are even supposed to know about his function- perhaps it is a hint of Fuji's trajectory with their X series cameras...

 

I think it is very interesting, and telling, that Mr Daniels mentioned (and praised) the X-100 when he was discussing (albeit broadly) future leica cameras...

 

is there any possibility of Leica working with Fuji? I have a feeling that Fuji will be making all new M mount lenses before we know it...

 

Imagine such a camera- macro and telephoto- and potentially the cleanest finder ever- flick a lever for EVF. Whatever lens you put on- a perfect full frame appears (change a setting for curved corners like the m3... call it M3 mode- or 'classic mode'). If you want other info in the finder you can have it all: if you don't- you can have the cleanest finder since the M3.

[pico]

I have the impression that the one area where retrofocus WA lenses are inherently superior is their relative freedom from of cos^4 vignetting [...]

 

I need some convincing, or rather instruction on that point. For example, I use two different obviously non-retro-focus 75mm lenses (one a Biogon) and one 3" Biogon lens for 4x5. The 3" lens does a very good job of minimizing the cos^4 because it covers 7x7", while the others just cover 4x5". It also focuses upon infinity with the rear lens less than one inch from the film and the rear element is 4.5" in diameter. Could not Leica make something similar? I realize that scale might be an issue. The 3" lens is huge. My FTP server is down or I would post a page on the later.

 

I have posted way too much today and am going for a walk. Got a a new, Amish made cane that I need again and I will focus my criticism upon it. Peace.

.

[giordano]

I need some convincing, or rather instruction on that point. For example, I use two different obviously non-retro-focus 75mm lenses (one a Biogon) and one 3" Biogon lens for 4x5. The 3" lens does a very good job of minimizing the cos^4 because it covers 7x7", while the others just cover 4x5". It also focuses upon infinity with the rear lens less than one inch from the film and the rear element is 4.5" in diameter.

 

The angle of view of a lens doesn't affect "cos^4" vignetting within that angle. Rather, the relevant question is, if you shoot the identical subject on 5x4 with the 75mm lenses and the 3" Biogon, are the corners of the 75mm images darker than those of the 3" image? Has to be a very small aperture (say f/32) to minimise optical vignetting.

 

I found a diagram of retrofocus vs non-retrofocus designs and how this affects cos^4 vignetting, including illumination charts for 21mm Distagon and Biogon designs: Vignetting.

 

Could not Leica make something similar? I realize that scale might be an issue. The 3" lens is huge. My FTP server is down or I would post a page on the later.

If your 3" Biogon covers 7x7 inches, that's a diagonal of 251mm and a 117.6 degree field of view. Scale everything down by 43.3:251 to get to FF and we get:

 

• Focal length: 13mm
  
• Diameter of rear element: 20mm
  
• Rear element to image plane: c. 4mm
  

A 20mm rear element is perfectly practical, but it would be getting very close to the M9 shutter!