Sweet spot of lenses

[Muizen]

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I wonder whether information exists regarding the so called "sweet spot" of Leica lenses?

[ho_co]

Andy Piper posted a conclusion some while back that with digital cameras, f/5.6 is as far as you want to stop down due to sensor diffraction.

 

General rule of thumb is, one to two stops down from wide open.

 

Erwin Puts' reviews, taken with the Leica-published data, will also give you pointers.

 

In practice, it's a meaningless question since the lenses can generally be used at all apertures.

[tdtaylor]

Need to remember that Leica lenses are often best wide open. This is very different than my Nikons, that while excellent lenses, often improve after stopping down a couple of stops. Most likely why the large difference in price tags

[Guest nafpie]

Need to remember that Leica lenses are often best wide open.

 

Probably in the center this may be true.

 

In the corners, even Leica lenses will benefit from stopping down a bit.

 

Stefan

[swamiji]

This question is just vague enough for fun... I would say behind... I would never want to be in front. All the other answers have been take in previous posts.

 

P.S. I have been told over and over that Leica lenses are best used wide open.

 

See: http://en.leica-camera.com/assets/file/download.php?filename=file_1758.pdf

[k-hawinkler]

This question is just vague enough for fun... I would say behind... I would never want to be in front. All the other answers have been take in previous posts.

 

P.S. I have been told over and over that Leica lenses are best used wide open.

 

See: http://en.leica-camera.com/assets/file/download.php?filename=file_1758.pdf

 

Yup, most useful. That seems to be the bible for the OP's question.

 

K-H.

[lars_bergquist]

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Humour an old pedant.

 

I do not know of any lens, Leica or not, that is best (optically best, i.e with the clearest definition) wide open. That would demand a lens that is completely devoid – and I mean that literally, in a technical sense – of all known aberrations. In that case, only diffraction would remain. This is a matter of natural laws, or to be exact, the wave nature of light. If only diffraction existed, a f:1 lens would automatically be better than a f:2 lens and better wide open than stopped down.

 

This holds true for all Leica lenses or other lenses that I have ever owned. In Leica's case, you can go to published MTF graphs for confirmation. The contrast curves rise on stopping down. Until the sinking level of aberrations is overtaken by the rising level of diffraction.

 

Now there are a couple of lenses that are actually (technically) about as good wide open as stopped down – moderately. These are moderate aperture lenses, e.g. the 24mm Elmar ASPH and the 90mm Macro-Elmar. Such lenses can be designed with a very high level of correction, meaning that aberrations and diffraction balance each other pretty completely. Otherwise, edge sharpness and micro-contrast improve until the lense goes "diffraction limited", which is usually at about 5.6, or 4 in some exceptionally well corrected lenses. The loss is very small up to beyond 8 however, and the general impression of sharpness may well continue to increase even beyond that, because of the greater depth of field. I don't hesitate to stop down to 11 if the subject demands it.

 

"Best wide open"? There's lots of sloppy thinking and talking here. "The lens is best wide open" is NOT the same thing as "I like the lens best wide open, 'cause that's the kind of picktjers I like". The technical quality of a lens, its "fidelity" if you like, is a measurable quantity, not amenable to hand waving. Pictorial preferences are.

 

The irritating old man from the Age of Evidence

[250swb]

The 'best wide open' mantra is utter rubbish if only for the way it can so easily be disproved. Have people not questioned it by making comparisons? But I think the term eminates from the 'best wide open' jockey's who's only reason to make a photograph is to leer over Leica bokeh. It keeps some people happy.

 

But the 'sweet spot' is itself a dangerous question if people take it the facts too far. There may be a perfect aperture to use to resolve a test chart, but in many cases and for many reasons it won't translate into a better photograph. And the difference in trying to use the 'sweet spot' in the field can mostly be outweighed by the stilted photographs produced. Using the best aperture (any) for the photograph is the sweet spot for the photograph, using the best aperture (f5.6) for the lens is the sweet spot of the test chart.

 

Steve

[markgay]

Maybe the OP is using "sweet" in the Urban Dictonary sense of the word:

 

"Something that is awesome"

[earleygallery]

As Mark says, it depend what the OP means by 'sweet spot' and it's a moot point at best.

 

The sweet spot is whatever you decide it to be. Could be the aperture you have to use to acheive correct exposure, could be f16 as you want as much DoF as possible, could be wide open on a Noctilux because what's the point of a Nocti if you're using it at f8 all the time?

 

If the OP wants to know what aperture typically gives best performance on any given lens then that has been answered above already.

[01af]

Maybe you want to read this.

[jaapv]

Humour an old pedant.

 

I do not know of any lens, Leica or not, that is best (optically best, i.e with the clearest definition) wide open. That would demand a lens that is completely devoid – and I mean that literally, in a technical sense – of all known aberrations. In that case, only diffraction would remain. This is a matter of natural laws, or to be exact, the wave nature of light. If only diffraction existed, a f:1 lens would automatically be better than a f:2 lens and better wide open than stopped down.

 

This holds true for all Leica lenses or other lenses that I have ever owned. In Leica's case, you can go to published MTF graphs for confirmation. The contrast curves rise on stopping down. Until the sinking level of aberrations is overtaken by the rising level of diffraction.

 

Now there are a couple of lenses that are actually (technically) about as good wide open as stopped down – moderately. These are moderate aperture lenses, e.g. the 24mm Elmar ASPH and the 90mm Macro-Elmar. Such lenses can be designed with a very high level of correction, meaning that aberrations and diffraction balance each other pretty completely. Otherwise, edge sharpness and micro-contrast improve until the lense goes "diffraction limited", which is usually at about 5.6, or 4 in some exceptionally well corrected lenses. The loss is very small up to beyond 8 however, and the general impression of sharpness may well continue to increase even beyond that, because of the greater depth of field. I don't hesitate to stop down to 11 if the subject demands it.

 

"Best wide open"? There's lots of sloppy thinking and talking here. "The lens is best wide open" is NOT the same thing as "I like the lens best wide open, 'cause that's the kind of picktjers I like". The technical quality of a lens, its "fidelity" if you like, is a measurable quantity, not amenable to hand waving. Pictorial preferences are.

 

The irritating old man from the Age of Evidence

 

According to Erwin Puts the Apo-Telyt 280/4.0 is diffraction limited wide open. I think one or two of the other long R lenses, inluding some combos in the Apo Module system are as well. But this optical stratosphere is indeed thinly populated.

[pgk]

Maybe the OP is using "sweet" in the Urban Dictonary sense of the word:

 

"Something that is awesome"

And for a lens to be 'awesome' it would presumably have to have a 'sweet spot' that would include both aperture and focus setting - ie where it performs at its absolute best. No doubt such a point exists and it will probably vary depending on whatever parameters are used to define it. But to be truly 'awesome' this spot would need to be significantly better than any other spot wouldn't it? So as far as I am concerned the answer is no. There are worse areas (don't use minimum aperture if you want maximum resolution, or don't use a fast aperture lens wide open and minimum focus and expect it to be as biting crisp as it is elsewhere) and better areas but at the end of the day its about utilising a good lens relevantly to the image being taken. IMHO most modern Leica M lenses are very competent performers indeed throughout their aperture and focus ranges and don't disappoint when used correctly.

[tobey bilek]

280 4.0 is diffraction limited lens. Only debth of field improved on stopping down.

 

Even the APO lenses are best one stop down. Older lenses two down.

 

What is nice is Leica lenses are more useable wide open compared to others, although Nikon and perhaps others have come a long way in 30 years.

[tdtaylor]

Guess the corrections of my comments are deserved- should have never commented after coming back from a good party having partaken in a little good single malt. One tends to be more philosophical than technical in that frame of mind. I still feels differently about the way I approach my Nikon lenses and Leica lenses in respect to aperture. With Leica, at least the lenses I have, I have little reservation of using them wide open, and often feel the opposite with my Nikon equipment (except the 14-24mm).

 

Ironically, as opposed to what has been put forth above, I am not obsessed with boken, although I do like to take advantage of it when appropriate. Most of my current work is architectural, so of course I know what aperture and distance on each lenses will provide me with the best edge to edge definition (after much practice and testing).

 

For those who's sensibilities I wronged by responding in a philosphical rather than technical manner, my apologies (I happen to be a registered Architect and register Engineer- guess the Architect came out ).

[250swb]

And for a lens to be 'awesome' it would....

 

For a lens to be 'awesome' it would need to be used by somebody wearing a baseball cap, who would like to thank the team down at the photo lab, his wife, his parents, God, the crowd who witnessed the photo being made, and most of all Leica for building the equipment without which he couldn't have taken the photograph.

 

Steve

[Overgaard]

I think about all viewpoints will fit into this.

 

Leica M lenses and M cameras are made for low light photography with available light, hence the rather extreme apertures, especially in these days where professional photographers discuss the need for faster lenses than f/2.8 if you anyways turn up the ISO (and their Nikon and Canon lenses anyways aren't good before f/4.0-f/5.6; this was a real discussion in the Danish Press Photographer Association forum just two weeks ago).

 

Leica M lenses are made for being used wide open, and if one examines the result of many of the new Summilux lenses, the amount of detail is amazing. It also goes with the territory of low light and available light, that you then use the DOF as an artistic tool, and if the corners are not as sharp as the center wide open - who would notice that the bokeh is a bit out of focus?

 

For landscape and other photography, Leica offer f/4 lenses as the WATE, and just as useless as it is to produce DOF and bokeh, just as useful it is to produce razor sharp images of landscapes and skyscrapers with sharp corners as well.

 

The depth of field calculations are the same for all lenses in the same focal length. So a f/1.4 Summilux stopped down to f/5.6 will be the same look - almost - as a f/5.6 lens, only the f/5.6 lens would be both more compact, lighter in weight, and cheaper to produce and buy.

 

But Leica M lenses tend to be low light lenses, and within that field Leica seem to have no considerations spending whatever efforts and exotic glass types to produce the best results possible. And given that, it would be stupid to buy a low light lens to use it as at f/4 to get sharp corners. Then it would be wiser to buy an f/2.0 or f/2.8 lens to begin with.

 

The S range is entirely different than the M, because most S2 cameras and lenses will be stopped down, because the target group for those lenses seek sharpness. The lenses work fine at f/2.5, but if sharpness of all details are the goal, you want lots of light and f/8 or less.

 

I like Erwin Puts' writings a lot, and all what he is saying is based on facts and is both true and useful. But when he says a lens is best at for example f/5.6, he's talking technically and not artistically best. One should choose lenses from the artistic look, the communication, one wants to have.

[aesop]

 

...<snip> I like Erwin Puts' writings a lot, and all what he is saying is based on facts and is both true and useful. But when he says a lens is best at for example f/5.6, he's talking technically and not artistically best. One should choose lenses from the artistic look, the communication, one wants to have.

 

...great to see that I am not alone. Thorsten, as far as I am concerned, you definitely "get it".

[k-hawinkler]

I think about all viewpoints will fit into this.

 

Leica M lenses and M cameras are made for low light photography with available light, hence the rather extreme apertures, especially in these days where professional photographers discuss the need for faster lenses than f/2.8 if you anyways turn up the ISO (and their Nikon and Canon lenses anyways aren't good before f/4.0-f/5.6; this was a real discussion in the Danish Press Photographer Association forum just two weeks ago).

 

Leica M lenses are made for being used wide open, and if one examines the result of many of the new Summilux lenses, the amount of detail is amazing. It also goes with the territory of low light and available light, that you then use the DOF as an artistic tool, and if the corners are not as sharp as the center wide open - who would notice that the bokeh is a bit out of focus?

 

For landscape and other photography, Leica offer f/4 lenses as the WATE, and just as useless as it is to produce DOF and bokeh, just as useful it is to produce razor sharp images of landscapes and skyscrapers with sharp corners as well.

 

The depth of field calculations are the same for all lenses in the same focal length. So a f/1.4 Summilux stopped down to f/5.6 will be the same look - almost - as a f/5.6 lens, only the f/5.6 lens would be both more compact, lighter in weight, and cheaper to produce and buy.

 

But Leica M lenses tend to be low light lenses, and within that field Leica seem to have no considerations spending whatever efforts and exotic glass types to produce the best results possible. And given that, it would be stupid to buy a low light lens to use it as at f/4 to get sharp corners. Then it would be wiser to buy an f/2.0 or f/2.8 lens to begin with.

 

The S range is entirely different than the M, because most S2 cameras and lenses will be stopped down, because the target group for those lenses seek sharpness. The lenses work fine at f/2.5, but if sharpness of all details are the goal, you want lots of light and f/8 or less.

 

I like Erwin Puts' writings a lot, and all what he is saying is based on facts and is both true and useful. But when he says a lens is best at for example f/5.6, he's talking technically and not artistically best. One should choose lenses from the artistic look, the communication, one wants to have.

 

 

Many thanks for your point of view.

 

Here is an interesting statement http://www.l-camera-forum.com/leica-forum/1613062-post9.html putting yours into perspective.

 

Best, K-H.

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Hallo,

Look here: Interesting Leica gear

[Overgaard]

It's hard to say what difference there is between 1950 and 2010 in terms of glass quality.

 

It's a fact that Leica uses many types of glass. I got some samples from the Noctilux, and you can tell from the look and the weight and the feel that it's different types of glass. Very different in fact-

 

The story in LFI referred to previously may give a hint. For the Noctilux it was necessary for Leica to get three new machines made especially for them to grind the aspherical glass in the new f/0.95, and each machine takes 2-8 hours to produce one glass (front or rear ASPH element), and then only some of them get through quality control (I got some with a red mark on, meaning they didn't fulfill specs).

 

If you look at the cost of producing the extra f/0.05 opening compared to the previous model, and at the same time maintaining weight and size with floating elements in the new one ... well, it's obvious that easier roads could have been traveled. And yet they did a f/0.95 which is kind of childish ;-). but still better performing than the previous models.

 

I don't know that for a fact, but the way I see the model is that Peter Karbe gets the idea or the assignment to produce a new lens with his department, and then they utilize the somewhat 2,000 glass patents Leica holds, all the written down knowledge since 1908 and perhaps even earlier, and then they set the bar a bit higher than previous models. And then that is what they come up with. And then somebody else in the factory has to figure out what the selling price has to be with those costs it takes to produce the wonders.

 

So far the strategy has worked well, we're all on the waiting lists for the most exotic lenses.

 

Part of all this figuring out specs, ways of producing, etc. may also include what is possible to get in terms of glass. The Thambar (1934) was said to be radioactive, and the first Noctilux lenses f/1.2 had some very very exotic glass types, which was one of the reasons it had to be redesigned. I guess they take environment, todays production facility possibilities, delivery time and all into account. But it's not my impression they try to economize ;-)

 

If you read the story about the Noctilux, it becomes a bargain. Amazing that it can even be bought by other than the royal family from Qatar!