Friday, October 18, 2019

APO-SUMMICRON-SL 35mm f/2 ASPH: SIMPLY STRATOSPHERIC


By José Manuel Serrano Esparza

There isn´t and there won´t ever be a perfect lens. Because however good an objective may be, it is always a balance between a myriad of variables.

Dietmar Stuible, optical designer at Leica Camera A.G, 
holding an Apo-Summicron-SL 35 mm f/2 ASPH.
© jmse 

Anyway, a lot of expectation has been raised regarding the new Apo-Summicron-SL 35 mm f/2 ASPH lens, whose MTF curves could be seen in the LHSA Annual Meeting held in Wetzlar (Germany) between October 4 and 7 of 2018.

It is highly probably a f/5.6 diffraction limited lens, having been optimized for f/2, f/2.8 and f/4 diaphragms, with an optical potential able to generate incredible image quality not only with 24 megapixel sensors like the one featured by the Leica SL mirrorless full frame, but with future sensors sporting between 40 and 120 megapixels.

Front area of the Apo-Summicron-SL 35 mm f/2 ASPH being held by Dietmar Stuible.
© jmse 

All hints clearly suggest that the Apo-Summicron-SL 35 mm f/2 ASPH is a truly stratospheric lens delivering exceptional image quality and boasting the reference-class mechanic construction typical in the German photographic firm.

Obviously, the 35 mm focal length is one of the most important ones, particularly in genres like photojournalism, travel photography, fashion, landscape, street photography and others, so this is a great piece of news.

But those exceedingly meaningful MTF charts of the Apo-Summicron-SL 35 mm f/2 ASPH are really amazing and distinctly show that the performance of this wideangle lens at its widest f/2 aperture is incredible:

- At infinity, the saggital continuous red line of contrast for 5 lp/mm (the highest one in the MTF graph) of the Apo-Summicron-SL 35 mm f/2 ASPH almost touches the top line of the chart of 100% contrast with a value about 98.9 %in the center of the image, in the center, about 98.2 % at 10 mm from the image center and 97.5% on the corners (the red line of contrast for 5 lp/mm of the Apo-Summicron-M 50 mm f/2 ASPH delivers a value on corners of 88% at 21 mm from the center of the frame).

Also at infinity, the discontinuous tangential red line of contrast for 5 lp/mm of the Apo-Summicron-SL 35 mm f/2 ASPH virtually superimposes with the aforementioned saggital continuous red line of contrast for 5 lp/mm during its whole path from image center to corners with almost identical incredible values.

- At infinity, the continuous sagittal red line of contrast for 10 lp/mm of the Apo-Summicron-SL 35 mm f/2 ASPH reaches a value of about 98% in the center of the image, about 97.5 % at 10 mm from the center and 97% on the corners (the continuous sagittal red line of contrast for 10 lp/mm of the Apo-Summicron-M 50 mm f/2 ASPH yields on corners a value of roughly 73% at 21 mm from the center of the frame).

- At infinity, the discontinuous sagittal red line of contrast for 10 lp/mm of the Apo-Summicron-SL 35 mm f/2 ASPH reaches a value of about 97.8% in the center of the image, around 97 % at 10 mm from the center and approximately 94.6% for the corners (here the discontinuous sagittal red line of contrast for 10 lp/mm of the Apo-Summicron-M 50 mm f/2 ASPH delivers a value on corners of 96% at 21 mm from the center of the frame).

- At infinity, the continuous sagittal red line of resolution for 20 lp/mm of the Apo-Summicron-SL 35 mm f/2 ASPH reaches around 91% in the center (roughly equalling the Apo-Summicron-M 50 mm f/2 ASPH) and around 87% on the corners (here the continuous red line of resolution of the Apo-Summicron-M 50 mm f/2 ASPH gets a value of 63%).

- At infinity, the discontinuous sagittal red line of resolution for 20 lp/mm of the Apo-Summicron-SL 35 mm f/2 ASPH is around 91% in the center (where it superimposes with the continuous red line of resolution for 20 lp/mm up to roughly 11 mm from the center, where both of them reach a value of around 93.5%) and a value on corners of approximately 87% (here the discontinuous red line of resolution for 20 lp/mm of the Apo-Summicron -M 50mm f/2 ASPH reaches a identical value of 87%.)

- At infinity, the continuous sagittal red line of resolution for 40 lp of the Apo-Summicron-SL 35 mm f/2 ASPH reaches a value of 91% in the center of the image (the continuous red line of resolution for 40 lp of the Apo-Summicron-M 50 mm f/2 ASPH gets a value of 73% in the center of the image), around 82 % at 10 mm from the center and around 77% on the corners, at a distance of 21 mm from the image center (here the continuous sagittal red line of the Apo-Summicron-M 50 mm f/2 ASPH reaches a value of 55% at 20 mm from the image center, thanks to a titanic effort made by Peter Karbe who managed to beat at this point the value of 53% at 15 mm from the center, while preserving a highly praiseworthy value of 54% on the corners).

- At infinity, the discontinuous sagittal red line of resolution for 40 lp reaches a value of 91 % (at this point the discontinuous sagittal red line of the Apo-Summicron-M 50 mm f/2 ASPH attains a value of 73.5 %), reaching a value of approximately 87% at 10 mm from the image center and getting a value of 68% on the corners (here, after a further optical feat accomplished by Peter Karbe, the discontinuous sagittal red line of the Apo-Summicron-M 50 mm f/2 ASPH yields a value of 69.5 %, the same one as at a distance of 14 mm from the image center and a stunning quality increase with a value of 70% at 15 mm from the center and 71.5% at a distance of 16.5 mm from the center, that´s to say a value very near the 73.5% of the image center in an area near the corner).

In addition, Leica has always deemed fundamental the feedback provided by professional photographers testing its new lenses before launching them into market.

Therefore, however impossible it may seem, these values would outperform the already stratospheric ones reached at its widest f/2 aperture by the benchmark Apo-Summicron-M 50 mm f/2 ASPH and would instantly turn the Apo-Summicron-SL 35 mm f/2 ASPH wideangle lens into the new world yardstick in its focal length and luminosity.

Peter Karbe, Head of Optics at Leica Camera A.G, currently the best optical designer in the world and one of the most important and influential ones in history along with Erhardt Glatzel, Ludwig Bertele, Max Berek and Walter Mandler, as proved by the rack of extraordinary Leica M, Leica S and Leica SL lenses created by him, along with his overall supervision Leica SL lenses designed by Dietmar Stuible and Siegrun Kammansapart from having fulfilled some further major technical feats like in 1993 with the Leica M6J, when he modified Willi Keiner´s Leica M2 0.72x viewfinder, increasing it up to 0.86x, raising the image field in almost a 20% (as well as expanding the rangefinder effective base from 49.9 mm up to 59.1 mm, augmenting the focusing precision with highly luminous primes between 35 and 75 mm shooting at full aperture and with longer focal length lenses at every diaphragm). 
 © jmse 
                                                                                                     
And this is even more difficult to believe if we bear in mind that as a general rule, any comparison between a reference-class 50 mm standard lens and a benchmark 35 mm wideangle one will be won by the former, because the wider is the coverage of a lens, designing and manufacturing difficulties increase in a geometric way, and much more if you want to confer a 35 mm lens the true apochromatic correction in the way Leica does it, id est, without any compromise.

But there´s more. It seems apparent that the Apo-Summicron-SL 35 mm f/2 ASPH outperforms the exceptional image quality delivered by the Apo-Elmarit-R 100 mm f/2.8, and its optical performance even beats the one delivered by the diffraction limited Apo-Telyt-R 280 mm f/4, whose stratospheric image quality is better at widest aperture than at f/5.6, f/8 and f/11 (diaphragms in which optical performance goes on being excellent).

As a matter of fact, in the MTF chart of the Apo-Summicron-SL 35 mm f/2 ASPH at its widest f/2 aperture, its saggital continuous and discontinuous red lines of contrast for 5 lp/mm and 10 lp/mm are nearer from the top 100% line than in the MTF chart of the Apo-Telyt-R 280 mm f/4, and the same happens with the continuous and discontinuous sagittal red lines of resolution for 20 lp/mm and 40 lines/mm.

The Leica Camera A.G headquarters at Leitz Park Building in Wetzlar has become an international benchmark hub of optical designing not only aimed at the creation and manufacture of lenses for 24 x 36 mm format M-System cameras and SL-System Cameras), but also for APS-C format with such superb lenses for Leica TL and CL cameras like the Summicron TL 23 mm f/2 ASPH (equivalent to a 35 mm in 24 x 36 mm format), the Leica Elmarit-TL 18 mm f/2.8 ASPH (a gorgeous and tiny lens equivalent to a 27 mm lens in 24 x 36 mm format, featuring 8 elements — four of them aspherical — in 6 groups, a length of 2,1 cm and a weight of 80 g) and Micro Four Thirds Format, where its collaboration with Panasonic has spawned such outstanding lenses like the Leica DG Elmarit 200 mm f/2.8 O.I.S (equivalent to a 400 mm f/2.8 lens in 24 x 36 mm format) redifining the concept of wildlife photography in synergy with the Panasonic G9 camera, the Leica DG Noctitron 42.5 mm f/1.2 ASPH, the Leica DG Vario-Elmarit 50-200 mm f/2.8-4 ASPH and others with which the image quality delivered by small sensors rises significantly.
© jmse

This way, it seems clear that the Apo-Summicron-M 35 mm f/2 ASPH is a landmark design in the History of Optics and by far the best 35 mm lens ever made for 24 x 36 mm format.

REMARKABLE VERSATILITY OF A NEW ALL-AROUND PERFORMER YARDSTICK 35 MM F/2 LENS FOR 24 X 36 MM FORMAT

If the Apo-Summicron-SL 35 mm f/2 ASPH is really as extraordinary as hints suggest and truly diffraction limited or very near it, it would have a highly versatile use:

a) At its widest f/2, f/2.8 and f/4 apertures in such photographic genres like photojournalism, street photography, fashion and travel photography.

b) Between f/8 and f/16 as a lens for landscapes, because the resolving power, contrast and sharpness yielded by this new Leica wideangle lens must be extraordinary, with exceedingly lavish detail and highly probably fantastic colours.

Needless to say that the results this amazing lens can obtain not only coupled to the 24 megapixel Leica SL full frame camera, but particularly attached to the 47 megapixel sensor of the new Panasonic SR1 full frame EVF camera can be truly spectacular.

And the potential of the full frame mirrorless EVF camera with Foveon 24 x 36 mm sensor that Sigma will launch into market in 2019 in synergy with the Apo-Summicron-SL 35 mm f/2 ASPH could likewise be remarkable, because when the photographic context enables enough light to pass through all the three layers of Foveon sensors and feed them with photons, RAW archives have a second to none sharpness, thanks to the absence of low pass filter, the lack of interpolation and a greater chromatic information, though it isn´t less true that this kind of multilayer Foveon sensors suffer more with flare, ghosting, residual chromatic aberrations and on using slow shutter speeds. Anyway, chances are that Sigma will do a strenuous effort with its new mirrorless EVF 24 x 36 mm format camera to fix those aspects as much as possible.

THE PINNACLE OF AN OPTICAL REVOLUTION WHICH STARTED IN 2008

Diagonal left view of the front element and barrel of the Apo-Summicron-SL 35 mm f/2 ASPH held by Dietmar Stuible, Optical Designer at Leica Camera A.G. As with other SL lenses, the machining of the anodized aluminum is top-notch.
© jmse

The Apo-Summicron-SL 35 mm f/2 ASPH is the evolutive apex of an optical revolution that began in October 2008 with the first prototypes of the 37.5 megapixel Leica S2 medium format camera attached to a Summarit-S 70 mm f/2.5 ASPH CS and featuring ISO 100 as only sensitivity.

David Farkas (one of the world´s leading authorities on Leica photographic gear and CEO of Leica Store Miami) explaining the features of the first prototype of Leica S2 medium format camera with an only sensitivity of ISO 100 held by Justin Stailey (then M System Product Specialist at Leica Camera A.G) inside the Brown Hotel of Louisville (United States) during the 40th Annual Meeting of the LHSA in October of 2008.
© jmse

That camera featured a 30 x 45 mm medium format sensor and the autofocus lenses created for it by Peter Karbe were then and keep on being the best MF objectives ever made.

And subsequent better versions like the Leica S Type 006 (2012-2015), Type 006 S-E (September 2014-2015) and Type 007 (August 2015 until nowadays ) offered increased sensor sensitivity, predictive autofocus, higher speed, improve handling and a number of enhanced functions.

The great Italian fashion photographer Amedeo M. Turello in front of the façade of the Leitz Park Wetzlar main building in 2014. As a user of the Leica S2, his unique images using outdoors natural light to reveal the true character of his models speak for themselves and ooze elegance, style, emotions and passion to spare, in addition to a simple production approach whose goal is to depict intimate moments. He was one of the first pros on the go to prove that the medium format Leica S System of cameras and lenses was the benchmark in image quality, full-fledged efficiency shooting handheld, ergonomics and viewfinder within its product segment, with an optical performance comparable to 4 x 5 large format analogue cameras, thanks to the S primes designed by Peter Karbe, the best MF lenses made in the world until now, something that will be significantly enhanced with the new Leica S3 medium format camera announced during the recent Photokina 2018, featuring a last generation 64 megapixel CMOS sensor, 3 fps (the fastest MF camera in existence), impressive high and very high up to 50,000 ISO capabilities, a dynamic range of fifteen diaphragms, new colour filters on the sensor for optimum colour reproduction attaining wonderful skin tones, and scheduled to be launched into market in 2019.
© jmse

The Leica S Medium Format Reflex System has been from 2008 hitherto the reference-class MF one in terms of image quality (comparable to 4 x 5 large format analogue cameras) and handling (optimized for shooting handheld, with a size slightly smaller than a professional 24 x 36 mm format reflex digital camera and a similar use convenience).

But the core of that system was the formidable assortment of MF lenses designed by Peter Karbe and making a flawless symbiosis with the 30 x 45 mm format Kodak CCD sensor and the superb Fujitsu Maestro DSP featuring R-80 and FR-V CPUs of the Japanese brand with VIWL architecture.

A host of highly innovative technologies were used in the manufacture of these amazing MF objectives, both in optical and mechanical spheres.

And among those MF autofocus lenses there are some benchmark MF primes like the 8 elements in 6 groups Summarit-S 70 mm f/2.5 ASPH CS, Summicron-S 100 mm f/2 ASPH, Apo-Macro-Summarit-S 120 mm f/2.5, Summarit-S 35 mm f/2.5 ASPH, Super-Elmar-S 24 mm f/3.5 ASPH and zooms like the Vario-Elmar-S 30-90 mm f/3.5-5.6 ASPH, all of them with their own integrated microchip for complete control of every function, in addition to the further availability of most of the S-System lenses in versions with central leaf shutters for maximum creative freedom when using additional lighting.

These milestone S-System medium format lenses are so perfect that they don´t need any software correction, and right off the bat they became a technological platform for Leica from the viewpoint of optical evolution of its lenses for different formats, to such an extent that the huge know-how and experience gleaned with their design and manufacture were seminal for the inception and production of the SL lenses, the best ones ever made for 24 x 36 mm format from 2015 onwards, something which has resulted in yardstick objectives like 

- The Summilux-SL 50 mm f/1.4 ASPH, by far the best standard f/1.4 lens ever made along with the Zeiss Otus 55 mm f/1.4.

- The Apo-Summicron-SL 50 mm f/2 ASPH.

- The Vario-Elmarit-SL 24-90 mm f/2.8-4 (the best standard zoom ever made, delivering image quality comparable to the first-rate Leica SL 24 mm, 35 mm, 75 mm and 90 mm primes).

- The stratospheric Apo-Vario-Elmarit-SL 90-280 mm f/2.8-5.6 ( whose optical performance with continuous sagittal line for 40 lp/mm in the center reaching 83% contrast at 90 mm f/2.8, 84% contrast at 160 mm f/3.5 and 81% contrast at 280 mm f/4 slightly beats the 80% center of the image contrast of the also stratospheric Apo-Telyt-R 280 mm f/4 at f/4 — though on the corners at f/4 the Apo-Telyt-R 280 mm f/4 goes on slightly getting the upper hand — , so this extraordinary zoom is one of the most commendable optical feats in the history of photographic optics).

But if the aforementioned Leica S and SL System lenses have meant a quantum leap in the evolution of photographic optics and will keep on being benchmark objectives for many years, however incredible it may seem, hints clearly suggest that the new Apo-Summicron-SL 35 mm f/2 ASPH is a further quantum leap in terms of image quality with which Leica Camera A.G has gone beyond itself.

How has Leica managed to create this incredible 35 mm f/2 ASPH lens?

Evidently, in the same way as happened with the previous Leica SL primes and zooms, the large L-Mount boasting a 51.6 mm diameter and an exceedingly short flange of 20 mm has been very important, together with new and breakthrough state-of-the-art technologies, particularly in the scope of aspherical lenses, significant advances in electromecanics making possible new approaches in optical designs and a higher manufacturing accuracy of optical elements, ultramodern production methods, highly sophisticated new hardwares and softwares, the powerful stepper motors for the autofocus, the drive for the aperture and the fast move of the elements used for focusing, a great knowledge on exotic optical glasses and their properties, tighter assembly tolerances in lenses, a steady improvement of the coatings and inner baffling to minimize stray light and reflections to enhance contrast in difficult lighting environments, a very precise centering of the optical elements, etc.

Peter Karbe holding an optical element of a Leica lens. As a Head of Optics at Leica Camera A.G, his labour supervising the Leica SL lenses designed by Dietmar Stuible ( a young and exceedingly talented optical designer who apart from a number of Leica SL lenses was the designer of the Vario-Elmar-S 30-90 mm f/3.5-5.6) and Sigrun Kammans (driving force of the famous Vario-Apo-Elmarit-R 70-180 mm f/2.8, author of the mechanic part of the Summicron-M 35 mm f/2 ASPH from 1997 designed by Peter Karbe, currently engineer at the Leica Sports Optics and together with Michael Hartmann, the mastermind behind many of the stunning Leica binoculars, the  international benchmark in this scope, with landmark devices such as the Leica Noctivid, on the brink of getting utter colour neutrality). has been essential, along with Leica state-of-the-art technologies in the manufacture of aspherical lenses, both those ones produced by means of pressure molding (used above all for wideangle lenses) and the ones made using CNC-controlled grinding and polishing machines (mainly used for longer focal lengths).
© jmse

But achieving that level of optical performance (slightly beating the cream of the crop of Leica R and SL teleobjectives) with a wideangle lens is something in the frontier of the impossible, making necessary to have tons of experience and proficiency in lens designing, particularly when it comes to choosing the best path from the different ones offered by the highly advanced optical designing softwares to get that impressive image quality even at full aperture and that extraordinary uniformity of performance at every diaphragm and focusing distance while simultaneously avoiding that size and weight increase hugely. And that is the most difficult task to attain for any optical designer.

 If it was´t enough with the Apo-Summicron-SL 35 mm f/2 ASPH, Leica Camera A.G announced during the recent Photokina 2018 in Cologne (Germany) that it will release three more Apochromatic lenses in 2020 : a 21 mm, a 24 mm and a 28 mm, stretching the true apochromatic correction up to the superwideangle realm, something really fascinating that seems to confirm that Leica has been thoroughly preparing with enough anticipation the L-Mount Alliance with Panasonic and Sigma and the new 24 x 36 mm digital sensors featured by the mirrorless full frame EVF 24 x 36 mm format cameras that both Japanese firms will launch into market in 2019, as well as paving the way for a new between 40 and 60 megapixel Leica SL 2 mirrorless EVF full frame camera that could perhaps appear in 2020. Needless to say that the second to none optomechanical quality of Leica lenses is a major factor enabling the German photographic firm to be able to flawlessly adapt to future sensors between 50 and 120 megapixels made by different brands which could appear in future. Such is the optical expertise of Wetzlar brand, whose young talents like Dietmar Stuible have had great teachers in world-class optical designers and engineers like Peter Karbe and Sigrun Kammans.
© jmse

The new Apo-Summicron-SL 35 mm f/2 ASPH means a historical landmark for the Wetzlar firm and an optical achievement in the border of the scientifically feasible, even being a more perfect lens than the extraordinary Summarit-S 35 mm f/2.5 ASPH medium format lens (partially boasting DNI of Walter Mandler´s 12 elements in 10 groups manual focusing Elmarit-R 19 mm f/2.8 Version 2 — made between 1990 and 2009 — in its 11 elements — two of them aspherical, the large front one with great curvature and the much smaller back one — in 9 groups optical formula ) for the 30 x 45 mm format Leica S cameras, and stretching the true apochromatic correction (indicating the highest optical quality and usually reserved for 50 mm or longer lenses) to the wideangle scope of 24 x 36 mm format, with unbeatable levels of resolving power, sharpness, contrast and duration in time, proving once more the huge optomechanical prowess of the Leica Camera A.G optical designing team made up by Peter Karbe, Sigrun Kammans and Dietmar Stuible.



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