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Why stop at f/16


bencoyote

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Why do Leica M Lenses only go down to F/16? (The only counter example is the Macro-Elmar-M 90mm) 

 

I know about diffraction and it is well known that most lenses vignette at least some when they are wide open why isn't it just as acceptable to know that most lenses will lose some sharpness at f/22. Other brands seem fine at f/22.  I only checked a few but it seems that most S lenses go down to f/22.

 

I also understand some of the challenges of making a sort of roundish aperture for wide angle lenses  e.g. f/22 on a 21mm lens would be less than a mm but for those standard or more telephoto lenses don't they stop down to f/22? 

 

Is there some deeper reason?

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If you look at the 21mm lenses, both the f/2.8 aspheric and pre-aspheric and current SE only go to f/16. The f/3.4 Super-angulon stops down to f/22 though. The difference may be in the aperture diaphragm which in the Super-Angulon is a simpler square affair rather than the multi-bladed diaphragms on the other lenses so diffraction aside (and it may be partially an answer), I'd guess its simply a physical problem to do with multi-bladed diaphragms on small wide lenses. S lenses are larger format which will change things too.

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If you look at the 21mm lenses, both the f/2.8 aspheric and pre-aspheric and current SE only go to f/16. The f/3.4 Super-angulon stops down to f/22 though. The difference may be in the aperture diaphragm which in the Super-Angulon is a simpler square affair rather than the multi-bladed diaphragms on the other lenses so diffraction aside (and it may be partially an answer), I'd guess its simply a physical problem to do with multi-bladed diaphragms on small wide lenses. S lenses are larger format which will change things too.

 

How can it be a problem when Zeiss can provide f/22 on all their ZM lenses? They're like 50-75% cheaper too, depending on the focal length and lens type - compared to the equivalent Leica lens.

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How can it be a problem when Zeiss can provide f/22 on all their ZM lenses? They're like 50-75% cheaper too, depending on the focal length and lens type - compared to the equivalent Leica lens.

 

I don't know, but the Biogon is bigger. Might be worth looking into the physical design placement of the diaphragm on the Zeiss designs relative to the Leicas (and cost has nothing to do with it). According to the wiki here the WATE goes to f/22 which suggests to me that its a design point rather than resolution as the alternative is that its simply down to the drop in resolution.

Edited by pgk
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Part of where I'm going with this question is that I was looking at my M lenses and other lenses and sort of thinking about how wonderfully small the M lenses are and one thing that I noticed was that the actual aperture mechanism seems nearer toward the front of the lens with RF lenses. With all the complaints about the size of SL lenses and even the newer TL lenses, I wondered if part of the trick in RF lenses allowing them to be so small has to do with the aperture being nearer the front of the lens. However, I wondered if that may have consequences like not being able to stop down as far. 

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Be careful @jdlaing: I was born 66 years ago when nothing seemed to matter, but isn't the term 'piker' or 'pikey' considered politically incorrect these days?

 

If you think that's politically incorrect, jdialing and I have lunch together on occasion.  You should hear how we talk to each other :)

 

edit:

Another thought,  We're both the same age as you, and you probably have to be in that age group to even consider using the word piker :)

Edited by Schrödinger's cat
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Why do Leica M lenses only go down to f/16? Just to irritate you, Ben. ;)

 

Seriously, there is not an obvious rhyme-or-reason. Nor is the f/16 limit across the board: 50 Elmar f/3.5 goes to f/22, 90 Elmarits (sans "Tele") - both the first (1960s) and last (1990s), go to f/22. Most (if not all) the 28 Elmarits go to f/22.

 

I would imagine there is a complex "design dance" for each lens, involving max. aperture, space for the blades to "hide" when not stopped down, overall optical design (where the aperture needs to fall between the elements), overall image resolution (when diffraction will cause a significant degradation) - and perceived "need" (in Leica's sole opinion) for the extra aperture and DoF with any particular lens.

 

Remember the custom Noctilux, where all the aperture markings except f/0.95 were blacked out, to imply "not to be used." ;)

 

A side note - the aperture mechanism (or at least the external ring) is "nearer toward the front of the lens with RF lenses" mostly because that is where it started out in 1925. The focus mechanism of an RF lens has to connect to the camera, while the aperture needs no such mechanical link - so they were stacked that way. Focus at the camera end of the lens, aperture ring at the "other" end. And still are.

 

Once SLRs came along, and added auto-stop-down, and metering, most* of THOSE lenses moved the aperture ring back close to the camera, to keep the mechanical cams and levers as short as possible. SLR focusing did not need any lens/camera communication, until auto-focus appeared 30 years later.

______

* exceptions being early Canon FL lenses. And Olympus OM, who wanted them up front for the "Leica" look and feel.

Edited by adan
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I recently found myself in a situation where I needed to use a 50mm lens and I needed the maximum possible Depth of Field. 

The resulting picture had to be pin sharp when printed A3 in B&W so I used 200 ISO, DNG on my M240 mounted on a tripod.

 

With some trepidation, because of the supposed detrimental effect of diffraction, I tried f/8, f/11 & f/16.

 

This taught me some interesting lessons:-

 

          Firstly the effect on Depth of Field was significant so the f/16 shot was the best visually,

         

         Second that the diffraction related loss of resolution / contrast was undetectable. 

 

         Third, as E. Puts has been saying for years, camera shake is by far the most important contributor to loss of definition.

 

The long exposures inherent when using small apertures require a tripod or other support, particularly in the digital era.

 

Anything hand held will never be able to reliably detect resolution / contrast loss due to diffraction or exploit the performance of modern Leica lenses.

 

Perhaps one reason why Leica are reluctant to offer f/22 etc. is the accuracy with which it can be reliably engineered.

Some years ago I was told by Leica UK that every aperture stop, on every lens, had to be accurate to within plus or minus 1/8 of a Stop.

Edited by Peter Branch
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Once SLRs came along, and added auto-stop-down, and metering, most* of THOSE lenses moved the aperture ring back close to the camera, to keep the mechanical cams and levers as short as possible. SLR focusing did not need any lens/camera communication, until auto-focus appeared 30 years later.

______

* exceptions being early Canon FL lenses. And Olympus OM, who wanted them up front for the "Leica" look and feel.

 

When the Canon FT came out in the 1960s, I switched to Canon from Pentax for SLR work, and appreciated the front-mounted aperture control as it was like Leica, which I also used. But after a year's use I found I would get uneven over-exposure to one side of the frame when using small apertures. Looking through the shutter I could see the lens didn't stop down fast enough under these conditions, and didn't reach a small opening until the curtain was halfway across the frame, on both my 50 f1.4 and 200 f4 FL lenses. That could be partly because of the linkage to reach the front mounted aperture ring, and because the camera just released the lens to close on its own spring force, rather than forcing it closed by the camera linkage.

i traded all my Canons on a Leicaflex SL

A few years ago I picked up another Canon FT with 50 and 200 lenses for nostalgia, and found the lenses had the same problem, until I stripped the lenses and cleaned off all the oil residue and polished the linkage parts with moly disulfide. 

There were reasons Canon changed the design for the FD series lenses.

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Why do Leica M lenses only go down to f/16? Just to irritate you, Ben. ;)

 

I would imagine there is a complex "design dance" for each lens, involving max. aperture, space for the blades to "hide" when not stopped down, overall optical design (where the aperture needs to fall between the elements), overall image resolution (when diffraction will cause a significant degradation) - and perceived "need" (in Leica's sole opinion) for the extra aperture and DoF with any particular lens.

 

Remember the custom Noctilux, where all the aperture markings except f/0.95 were blacked out, to imply "not to be used." ;)

 

A side note - the aperture mechanism (or at least the external ring) is "nearer toward the front of the lens with RF lenses" mostly because that is where it started out in 1925. The focus mechanism of an RF lens has to connect to the camera, while the aperture needs no such mechanical link - so they were stacked that way. Focus at the camera end of the lens, aperture ring at the "other" end. And still are.

 

Once SLRs came along, and added auto-stop-down, and metering, most* of THOSE lenses moved the aperture ring back close to the camera, to keep the mechanical cams and levers as short as possible. SLR focusing did not need any lens/camera communication, until auto-focus appeared 30 years later.

______

* exceptions being early Canon FL lenses. And Olympus OM, who wanted them up front for the "Leica" look and feel.

 

I bet that you nailed it with the space needed to hide the blades combined with the narrowness needed to not block the RF, the precision of the stops required on a film camera, and the focusing needing to be at the back of the lens. That makes a lot of sense. 

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Correct, Ian - the clearest "sense" of the word is "someone who won't put their money where their mouth is." Cheap, but with the added implication of an unwillingness to commit themselves or face risk. No ethnic connection.

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To put it in the simplest of terms, shorter lenses do not need smaller apertures than f/16 to achieve the goals of having smaller apertures. 

 

When I used to shoot with a Nikkor 200mm f/4 micro lens, the minimum aperture it had to offer was f/32.  Why?  not because the lens was intended for photographing the sun.  It was to produce more depth of focus when shooting macro.   

 

By way of example, the Rodenstock APO-Sironar-S 360mm f/6.8 has a minimum aperture of f/64 for use on an 8x10 view camera.  

 

Small minimum apertures are not always about exposure.

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Correct, Ian - the clearest "sense" of the word is "someone who won't put their money where their mouth is." Cheap, but with the added implication of an unwillingness to commit themselves or face risk. No ethnic connection.

 

In Oz we use "piker" to describe some one who won't join in on a group activity. "Come on mate, don't be a piker". An example of it's use might be to convince someone who might be slightly afraid of doing something like going home to their significant other instead of to the pub with their mates.

 

Gordon

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Hello Everybody,

 

Most Leitz/Leica lenses that are F2 or faster close down to F16 or to a larger aperture.

 

Most Leitz/Leica lenses that are F4 or slower close down to F22 or to a smaller aperture.

 

In between F2 & F4 there is a mix.

 

This MIGHT mean that the parameters for smaller minimum apertures MIGHT be related in some manner to correction of image abberations related to maximum aperture correction as opposed to correction for focal length alone.

 

Best Regards,

 

Michael

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With some trepidation, because of the supposed detrimental effect of diffraction, I tried f/8, f/11 & f/16.

 

This taught me some interesting lessons:-

 

          Firstly the effect on Depth of Field was significant so the f/16 shot was the best visually,

         

         Second that the diffraction related loss of resolution / contrast was undetectable. 

 

         Third, as E. Puts has been saying for years, camera shake is by far the most important contributor to loss of definition.

 

 

Peter, I've done this experiment and found the effect of diffraction significant.  When shooting landscapes with a close foreground now I use f/5.6 or f/8 and focus stacking.  For a while I was also shooting an f/16 frame to compare and I finally stopped doing that because I almost never ended up using it.  It was always slightly soft by comparison.  Maybe I've tricked myself and the difference is in my head (I never did a blind comparison) but I don't think so.

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