miércoles, 21 de octubre de 2015


Text and Photos : José Manuel Serrano Esparza

The path started by Canon with its superb rectilinear 11-24 mm f/4L extreme wideangle zoom lens featuring 16 elements ( for of them aspherical — one of them handcraftedly grounded — 1 Super ED, 1 ED, and boasting super spectra and fluorine multicoating) in 11 groups for 24 x 36 mm format has brought about from the very instant of its introduction in February 2015 huge levels of expectation and even bustle in the photographic market, due to a number of significant reasons, particularly the fact of stretching the range of short focal lengths in nothing less than 3 mm in comparison to the likewise superb Nikon AF-S Nikkor 14-24 mm f/2.8G ED for full frame format (launched into market in August 2007 and being the benchmark in this type of zoom lenses hitherto).


The manufacturing of the Canon EF 11-24 mm f/4L USM zoom lens requires a great investment both in highly sophisticated and accurate specific CNC machines which have to be handled by very experienced personnel and top-notch optical designers with deep knowledge on the magneto reological finishing techniques with MRF tools, specially regarding six of its 16 elements: a very large aspherical one and hand grounded with a huge diameter of 87 mm, another one also aspherical and moulded in glass, two further smaller aspherical ones likewise moulded in glass, another one made with extra low chromatic dispersion Super ED glass and one more very low chromatic dispersion  UD glass.

Cross section of the impressive optical scheme of the 16 elements in 11 groups Canon EF 11-24 mm f/4L USM extreme wideangle zoom which has meant a turning point in the design and construction of this kind of variable focal length lenses, on having widened the ultrawide range up to 11 mm, even beating the barrier of 12 mm of the non retrofocus Voigtländer Heliar 12 mm f/5.6 super wideangle prime, something that can be bluntly defined as a feat, since the Canon zoom is a retrofocus design created to be used with full frame reflex professional cameras and in which the king size (nothing less than 108 mm) front bulbous lens moves when focusing, with a minimum focusing distance changing according to the used focal length: 32 cm in the 11 mm position and 28 cm in the 24 mm one.

The production cost of this extreme wideangle zoom lens is very high and it inevitably has an effect on its price tag of roughly 3,000 euros, which it certainly deserves, because it makes up in itself an important optical and mechanical chef-d´oeuvre entailing a qualitative leap and a spectacular extension of the extreme wideangle coverage with respect to the way opened by other two élite ultrawideangle zoom lenses, a rectilinear one yielding a stunning level of distortion correction, barely noticeable fall-off even in the shortest focal lengths and a remarkable uniformity of excellent image quality in center, border and corners (the Olympus Zuiko Digital 7-14 mm f/4 ED) and an exceedingly versatile further one, not so superlatively well corrected in distortion and vignetting but sporting an important f/2.8 widest aperture, delivering exceptional levels of resolution and contrast and which is until now the reference-class zoom lens for 24 x 36 mm format sensor cameras in the sphere of reportage and landscape photography (the Nikon AF-S Nikkor 14-24 mm f/2.8G ED):
- The Olympus Zuiko Digital 7-14 mm f/4 ED zoom lens for Four Thirds System, equivalent to a 14-28 mm f/4 in 24 x 36 mm format, introduced in September 2004, with an optical formula featuring 18 elements in 12 groups (two of them being aspherical — the second one manufactured with a topflight grinding, great diameter and a more than daring curvature along with a remarkable thouroughness in the cutting of its borders and the much smaller sixteenth one made with ED glass — , two Super ED ones — the forth and the sixth, the latter being a bit smaller — , and one ED — the fourteenth — ) and a weight of 780 g. It is still the yardstick in this domain an one of the greatest accomplishments in the whole history of photographic lenses, with an incredible level of optical correction: virtually lacking any geometric distortion, an extremely low fall-off for such a wide coverage lens and an unknown hitherto homogeneity of very high definition and contrast between center and corners in a zoom of this kind until its launching into market, even at 7 mm (thanks to the preservation of some colour fringing in the extreme short focal area), always bearing in mind that within the huge complexity and merit which takes designing a first-rate extreme wideangle zoom like this, it´s easier and with a lower production cost to do it for 4/3 format, Micro 4/3 or APS-C than for 24 x 36 mm format.
- The Nikon AF-S Nikkor 14-24 mm f/2.8G ED. Introduced in August 2007. A real flagship standing out forits great luminosity for such an extreme zoom featuring those traits and designed for full frame sensors and particularly because of its extraordinary resolving power and contrast in the center, in addition to excelling in its awesome evenness of optical performance at every diaphragm between f/2.8 and f/11 and in every and each of its focal lengths (even outpeforming in this sphere the superb Leica Vario-Elmar-R 21-35 mm f/3.5-4 ASPH, which is highly commendable, for the AF-S Nikkor 14-24 mm f/2.8G ED reaches a 7 mm wider angular coverage, so its design was much more difficult and greater the investment on its development), also delivering splendid colours, whereas on the corners there´s a slight qualitative decrease at f/2.8 which approaches results in the image center from f/4.

Nikon threw itself into this zoom making use of its whole optic and mechanical know-how, with an optical scheme featuring 14 elements in 11 groups (three of them aspherical ones and 2 ED), 9 diaphragm blades and and extensive use of nanocrystal glass, with a very good correction of vignetting, whose values are negligible to practical effects even at full f/2.8 aperture, far superior in this respect (in the same way as the others) to the Nikkor 16-35 mm f/4 VR.

Obviously, a lens encompassing this range of ultrawideangle focal lengths, constant f/2.8 widest aperture and a superb entirely metallic construction (with the exception of the plastic shade) can´t be small, so its dimensions are 9,8 cm diameter x 13,5 cm length and its weight 969 g.

It´s a true all-around performer, both in reportage and landscape photography, with the exception of architecture photography where the distortion correction of the Olympus Zuiko 7-14 mm f/4 and the Canon EF 11-24 mm f/4L USM is superior.

Nevertheless, the distortion correction in the AF-S Nikkor 14-24 mm f/2.8 is very acceptable, since it only exhibits a slight barrel one between 14 and 19 mm, which disappears from 20 mm and an even smaller, barely perceptible pincushion distortion at 24 mm.


The very complex and exotic optical scheme of the extreme super wideangle Canon 11-24 mm f/4L zoom lens boasting 16 elements (a very large 87 mm diameter handcraftedly ground one, a further one also aspheric and very big moulded in glass, two more smaller aspherical ones likewise moulded in glass, another one made with extra low dispersion Super ED glass and a further one made with very low chromatic dispersion UD glass) defines by itself the huge designing effort, integral use of opto/mechanical know-how and the manufacturing difficulties to produce a hallmark zoom lens with these specs, delivering an excellent optical quality throughout its whole focal range, along with a praiseworthy distortion correction for such an exceptionally angular coverage.

Needless to say that during the manufacturing stage there´s a high percentage of discarded optical elements, specially the 87 mm grounded large aspherical front lens needing manual cutting of extraordinary accuracy by a highly experienced optician, in adition to the use of breakthrough engineering and different ultramodern technologies bringing about some days to make it. It all results in a very high production cost of this excellent ultra wideangle zoom lens.

To that one should add the peculiar fact that there is a key conceptual affinity between the great attention paid by Canon to the design of the shape and curvature of the second aspherical element of the 11-24 mm f/4L zoom lens, which is very important for its final optical performance and pivotal regarding the huge personality of this zoom lens, and the likewise major significance which was given in the design of the Leica Super-Elmarit-R 15 mm f/2.8 to the shape and curvature of its second element (being the only aspherical one of its optical scheme) located behind the very big front lens.

On the other hand, in the same way as happens with the Nikkor 14-24 mm f/2.8G ED - also designed for 24 x 36 mm sensors - , the Canon EF 11-24 mm f/4L USM has been much more challenging to make than the Olympus Zuiko 7-14 mm f/4 ED for 4/3 system and that the Olympus M. Zuiko Digital ED 7-14 mm f/2.8 Pro for Micro 4/3 (the latter featuring an excellent correction of distortion by means of software algorithms and rendering its maximum image quality at 14 mm — equivalent to 28 mm in full frame — and very good at 10 mm — equivalent to 20 mm in 24 x 36 mm format — , while at 7 mm — equivalent to 14 mm in full frame — it is very good in the center but rather inferior on the corners, even stopping down) and with a much higher production cost, because manufacturing such a pure and exceedingly wideangle design, practically without any distortionand with a high uniformity of performance betwen center and corners for the image circle inherent to the 24 x 36 mm format (with an area of 864 mm2) a 400% bigger than the Four Thirds 17.3 x 13 mm format (with an area of 225 mm2) one means tackling far more complex optical requirements and assume physical challenges often in the boundary of the scientifically feasible, above all the more they take the shortest focal length to the limit, and in this respect, the 11, 12 and 13 mm in the extreme angular range of the Canon EF 11-24 mm f/4L USM are undoubtedly a compelling submission of credentials.

Neither should it be forgotten that designing and manufacturing wideangle and standard lenses for Four Thirds, Micro Four Thirds and APS-C giving fewer divergent rays on the margins of the image field is easier and with a much lower production cost than designing and manufacturing lenses for 24 x 36 mm sensors doing the same, particularly with wideangles, because the more oblique are the light rays reaching the sensor, greater is the possibility of color, vignetting and background noise errors to happen, unlike the tele lenses whose emergent light rays are almost parallel.

Additionally, the Canon EF 11-24 mm f/4L USM is a more laudable, advanced and difficult to achieve optical design both from an optical and mechanical viewpoint than the superb AF-S Nikkor 14-24 mm f/2.8G ED, since stretching the range of wideangle focal lengths from 14 mm to 11 mm geometrically increases the intricacies of manufacturing and insertion of elements and optical groups inside the lens and tolerances must be much more stringent, in addition to the fact that its distortion correction is better, to such an extent that it can be used in outdoor and indoor architecture photography, even at 11, 12 and 13 mm, which is a real and historical deed, as well as making up a zoom lens that will open new creative and composition chances in the fields of indoor photography, architecture, industrial photography, landscape, weddings and all kind of events with attendance of many people, environments in which it copes at great level.

Notwithstanding, as it happens with every lens whether it is a prime or a zoom, none of them is perfect, and it isn´t less true that the AF-S Nikkor 14-24 mm f/2.8 is also a fantastic ultra wideangle professional zoom lens, superior to the Canon EF 11-24 mm f/4L USM at full maximum aperture (f/2.8) and slightly better in resolution and contrast — both of them are excellent in these two parameters — , sides providing it with some substantial advantages and turn it into a better choice in photojournalism, landscape (though in this photographic genre things equal very much, because the 11, 12 and 13 mm available in the Canon zoom can make a difference when it comes to photograph landscapes in which you need maximum possible coverage), astrophotography and fashion.

From an optical standpoint, it´s presently impossible to get a 100% uniformity of performance in center, borders and corners in all the range of focal lengths covered by such an extreme ultra wideangle zoom lens like this including the rectilinear focal lengths of 11, 12 and 13 mm in its shortest stretch and the 24 mm in its longest one.

Therefore, Canon has made a tremendous designing effort in which priority is mostly given to the 16, 17, 18, 19 and 20 mm middle focal lengths of its range from the viewpoint of the obtention of a greater homogeneity of excellent performance in center, border and corners ( the qualitative peak of this flagship being 16 mm at f/8 and f/11), but with a fundamental goal: attaining as much resolution and contrast as possible in the center in the shortest mort extreme 15, 14, 13, 12 and even 11 mm focal lengths, greatly equalling (and this is an exceptional optical accomplishment) the values of definition and contrast on the image center in the aforementioned middle focal lengths, though with an inevitable drop in resolution and contrast in borders and corners (albeit quality of image keeps on very good in those areas for a zoom with this impressive rectlinear angular coverage) at all diaphargms and focusing distances.

Canon has apllied the practical guideline of mostly enhancing the maximum possible reduction of distortion, leaving it in commendable values, almost imperceptible, in pincushion for the long and middle focal lengths (between roughly 24 mm and 19 mm ) and in barrel (for the focal lengths between around 16 mm and 11 mm, the latter being inevitably the one in which it is more visible — with approximately a 3.8 % — ), with excellent and above all surprising values for such a hugely angular lens, something exceedingly difficult to attain, at the expense of intentionally preserving the visible chromatic aberrations inherent to 12 mm and specially 11 mm on the corners, in addition to an apparent fall-off in the 11 mm position at full f/4 aperture (tolerable, since it enables a very good resolution, great contrast and a more than acceptable distortion correction at that so extremely short focal length — to name only an example, the Super-Elmarit-R 15 mm f/2.8 ASPH has a 2% barrel distortion — ), always considering that there´s visible darkening on corners at maximum f/4 aperture in every focal length (including 1.5 EV in 24 mm position at f/4), but it disappears from f/5.6 between 12 and 24 mm.

And this sensational correction of distortion in a zoom lens with such a giant angular coverage as the Canon 11-24 mm f/4L making possible to do architecrure photography with it even at 11 mm, does constitute by itself a relevant milestone in the history of photographic lenses, being currently the most angular rectilinear professional zoom in the market, with the added bonus that it yields excellent resolution and contrast in the center at every focal length and diaphragm, including f/4, keeping very good values (only slightly inferior) on the corners, coma has been almost utterly eliminated and flare control is more than remarkable thanks to the Wavelength Structure Coating (SWC) and Air Sphere Coating (ASC).

All of its is exceedingly admirable in a lens starting at 11 mm and having marked a turning point in the History of Photography in this kind of ultra wideangle zoom lenses.

On the other hand, to properly grasp the meaningful achievement attained by Canon with the increase of the ultra angular coverage from 14 mm to 11 mm in its true dimension, it is important to be cognizant of the fact that until very recently it was believed little short of unfeasable within the ultra wideangle scope the construction of high end rectilinear extremely angular lenses boasting excellent correction of the distortion for reflex cameras under the barrier of 13 mm embodied by the mythical 16 elements in 12 groups Nikkor F 13 mm f/5.6 featuring optical correction for very short focusing distances through rear floating elements, integrated multicoatings and 7 diaphragm blades, designed by Ikuo Mori in 1971 and whose first prototype was built by Nikon in 1972, which is beaten by the new Canon EF 11-24 mm f/4L USM zoom lens nothing less than in 2 mm in its shortest focal length.


The Canon 11-24 mm f/4L is practically free of coma aberration at widest f/4 aperture in all its focal lengths and diaphragms, something hugely revealing, in the same was as the fact the Nikkor 14-24 mm f/2.8 lacks almost any coma even at full f/2.8 aperture, where its values in this regard are negligible and wholly disappear from f/4.

People buying a professional lens (with the exception of the photographers specialized in night photography and astrophotography), whether it is a prime or a zoom lens, don´t usually have coma correction among their top priorities, and above all lust for a very wide diaphragm aperture, maximum feasible resolution and contrast, an excellent correction of distortion, a good reduction of the fall-off at the most luminous f stops, a first-rate antirreflective coating, etc.

That´s why on designing and manufacturing excellent highly luminous wideangle lenses with maximum apertures between f/1.4 and f/2.8 which excel in those parameters mostly longed by both professional and advanced connoisseurs, the whole design is often optimized holding on to an intentional lack of integral attention to coma correction during the development of the optical formula, the tests with MTF curves, etc, because coma won´t be a decisive aspect in photographic genres like architecture, landscape, indoor photography, creative fashion with widest diaphargms, etc, and the preserving of a certain degree of coma at maximum aperture which dispappears on stopping down two diaphragms is the usual resource, because it enables to focus the inherent compromises to any optical design — however good it may be — in favour of the aforementioned parameters.

That´s for instance what happens with the Canon 24 mm f/1.4L II and the Sigma Art 24 mm f/1.4 DG HSM, both with visible coma at f/1.4 and f/2, which in the Sigma lens greatly disappears at f/2.8 and in the Canon lens at f/4.

On its turn, the Samyang 24 mm f/1.4 ED AS IF UMC Aspherical is already virtually free of coma aberration at f/2 and very reduced at f/1.4, but its distortion correction and its values of resolution and contrast — though being good — are clearly inferior to the Canon 24 mm f/1.4L and the Sigma Art 24 mm f/1.4 DG (the latter being the one featuring more global quality among the three), because equalling the resolution and contrast of both the Canon and Sigma wideangle lenses simultaneously keeping their excellent correction of the coma at full aperture would have significantly increased the design and production cost, along with their quality level, and their price would have inevitably been much higher.

Besides, it´s also very meaningful the fact that the Canon 11-24 mm f/4L beats clearly the Canon EF 14 mm f/2,8 L II and the Canon 16-35 mm f/2.8 L II in all of its focal lengths and diaphragms regarding coma correction and definition in borders, and delivers some less distortion in 14 mm position than the Canon EF 14 mm f/2.8 L II and less distortion at 16, 17 and 18 mm than the Canon 16-35 mm f/2.8 L II.

As to flare control, from the very beginning of the design of its 11-24 mm f/4 L, Canon was perfectly aware that this was going to be one of the key and most difficult to deal with, because the widening from 14 mm to 11 mm in the shortest angular range results in a huge increase in both the possibilitiy that reflections can appear and the difficulties to control them in comparison to 14, 15 and 16 mm primes or zooms starting from 14 mm.

Consequently, an independent research department was created aiming at looking for the best feasible solution to this subject, and after a lot of tests, they opted for a symbiosis between the large two first aspherical front lenses and the fourth element located between the third aspherical lens and the Super ED element, adhering Subwavelength Structure Coating (SWC) on the inner face of the complete curvature of the very big aspherical elements 1 and 2 and Air Sphere Coating (ASC) on the whole straight surface of the outer face of the Super ED element.

It all brings about an outstanding enhancement of contrast, which remarkably fosters the visual perception of sharpness and capturing of details already excellent in this zoom.
But if all that were not enough, fully grasping that it´s not possible to attach the typical UV or protective filter (something also happening with the Nikkor 14-24 mm f/2.8), Canon has likewise paid great heed to avoid by all means that dust, dirtiness or water drops can adhere both to the large part of the very big area of the lens (108 mm diameter) and to the back one, something extremely difficult, particularly with regard to the great surface of its front area.

Anyway, Canon has managed to do it by means of a very advanced Fluorine Coating boasting impressive antiadherent properties and covering the whole surface of the external curvature of the huge 87 mm aspherical front lens handcraftedly ground and also all the straight rear surface of the aspherical lens (much smaller and glass moulded) of the back area, and which is the nearest to the sensor when the lens is coupled to the camera.

To get an idea of what the Canon 11-24 mm f/4L has meant in the history of photography, the Samyang 14 mm f/2.8 IF ED UMC fixed lens exhibits an extraordinary correction of coma, to such an extent that at 12 and 13 mm it has better distortion correction than the Samyang 14 mm f/2.8 Aspherical, also outperforming it in resolution and contrast, while its optical design has preserved a virtually total reduction of coma aberration at maximum f/4 aperture thanks above all to the interaction between the four aspherical elements (three of them placed in the front area and the other one at the end of the rear area), the Super UD element of the front area and the UD element of the back area of the zoom lens.

This way, the fact that much more attention than usual has been paid to the correction of coma at the widest f/4 aperture in the Canon 11-24 mm f/4L bearing in mind the excellent values of resolving power, contrast, incredibly good correction of distortion and the huge super angular coverage up to 11 mm it offers and commendably reduced vignetting, distinctly indicate that it is a cream of the crop zoom lens in which each and every one of the myriad of optical and mechanical sides coming into play have been painstakingly analyzed and large amounts of money have been invested on R + D in synergy with a strenuous effort of design and manufacturing, something likewise happening as to this aspect with the Nikkor 14-24 mm f/2.8 ( a more praiseworthy design in this side than the Canon, always considering that it would be impossible to create a Canon 11-24 mm f/2.8 with the optical and mechanical quality of the Canon 11-24 mm f/4L without an increase in more than double of both weight and size), whose barely perceptible values of coma at f/2.8 and its elimination at f/4 make it even more adequate for night photography and astrophotography, in which the maximum possible capturing of light is necessary, so it is better to have a f/2.8 or even a wider aperture available.

To get with such an extremely angular zoom lens as the Canon 11-24 mm f/4L or the Nikkor 14-24 mm f/2.8 to integrate a practical elimination of coma at maximum diaphragm aperture with the rest of qualities mostly sought after by professionals on acquiring an élite zoom is something exceedingly complex which increases geometrically if you want to reduce Seidel aberrations as much as possible, since to achieve that reference-class qualitative level it is unfeasable to efficiently control every parameter through optical systems whose tracing of luminic rays is only set up by computers and designing softwares, however leading-edge they can be, and at least one optician with tremendous knowledge and experience and knowing the decisions to make will be necessary.


Canon has also paid great attention to the design of the diaphragm of its 11-24 mm f/4L zoom, providing it with nine blades with a thoroughly studied shape to synergize to the utmost with the Subwavelength Structure Coating (SWC), Air Sphere Coating (ASC) and Fluorine Coating it includes in its optical formula, which strengthens even more the excellent flare reduction characteristic of this zoom lens, and in addition, it renders the sun appearing in landscape photographs as a beautiful 18 point star.


A further reason for the high production cost of very sophisticated lenses boasting top-notch optical and mechanical performance is the massive percentage of discarded out of tolerances elements, because the more their performance is, more will have to be the accuracy with which they are cut, ground and covered with antirreflection coatings, so above all the four aspherical elements of its optical formula (particularly the first one — with a huge 87 mm diameter and manually cut — and the second one — also featuring a large diameter, glass moulded and even more interesting from an optical viewpoint — ) of the new Canon EF 11-24 mm f/4L zoom lens need amazing accuracy and it can take some days to configurate them, so an unavoidable quantity of time must be devoted to it and to production capacity.

Besides, if there´s the slightest deviation of tolerance or decentering, it´s not possible to use the resource (of which designers can sometimes get advantage with intermediate and high level lenses) of counteract the effect generated by that deviation using another optical element featuring opposed traits to neutralize it.


The exceptional qualities of the Canon 11-24 mm f/4L regading its stunning extreme great angular coverage, its hugely praiseworthy correction of geometric distortion, its excellent values of resolution and contrast specially at the shortest and middle focal lengths at maximum aperture f/4, the full professional effectiveness of its 11, 12 and 13 mm, its remarkably well corrected fall-off (particularly if we bear in mind that it is the most angular rectilinear lens in the market), its very advanced and exotic optical formula with profusion of high-end aspherical elements both ground and glas moulded (specially the exceedingly difficult to build and very high production cost elements 1 and 2 sporting a large front diameter), etc, are fruit of two key factors:

a) The very strong presence and prestige of the AF-S Nikkor 14-24 mm f/2.8G ED in the photographic market.

b) The introduction by Canon of its new professional reflex cameras Canon 5DS and 5DSR with 50 megapixel full frame sensors, much more exacting with lenses attached to them than the 24 or 18 megapixels of also professiona reflex cameras like the Canon EOS 5D Mark III or the Canon EOS-1D X.

It seems apparent that the Canon 11-24 mm f/4L was designed from scratch with the fundamental need in mind of obtaining its best possible interaction with the new 50 megapixel 24 x 36 mm format sensors of its new professional reflex cameras and other new ones that can appear in future.

It will be interesting to see the market evolution and if this surge in megapixels becomes a future trend market in the full frame professional scope, because it is evident that 36 megapixel cameras like the Nikon D800, D800E and Sony A7r, the APS-C format 16 megapixel  Fujifilm X-T1, the Micro 4/3 format 16 megapixel Olympus E-M5 MK II, the Micro 4/3 format 16 megapixel Panasonic Lumix GH4 Micro 4/3 and others are highly advanced utterly professional cameras rendering excellent image quality, as well as enabling to get very big enlargements on photographic paper in sizes which were unthinkable only a few years ago (above all the APS-C and Micro 4/3 ones) and fulfill most assignments of the photographers using them, so deeming as an absolute necessity to have a camera featuring a 50 megapixel sensor (something that undoubtedly has got its advantages) would be a fallacy, since cameras are first and foremost photographic tools whose aptness would greatly depend on the kind of work to do.

On the other hand, the increase in sensor resolving power up to 50 megapixels with reflex cameras featuring pentaprism, reflex mirror and abundant moving parts entails more drawbacks than the hypothetical design of breed of mirrorless full frame 24 x 36 mm sensor cameras featuring electronic VF like the Sony A7r but with 50 megapixels with respect to vibrations, wearing away and very specially the creation of specific lenses for such powerful sensor, because the lack of swivelling mirror and a smaller flange distance than in full frame dslr cameras allows to conceive more pure optical designs without compromises and manufacture even better lenses.


The Canon 11-24 mm has inaugurated a new era in the design and manufacture of ultrawide zoom lenses, with staggering levels of resolution, contrast and correction of distortion if we consider that it begins at nothing less than 11 mm in its shortest extreme stretch, excellent control of flare by means of two state-of-the-art multicoatings in symbiosis with a further very advanced multicoating avoiding the adherence of water drops, dirtiness and dust both on the huge bulbous front lens and the back area of the aspherical element 4 — the nearest to the sensor — and the most exotic and complete optical formula made incepted hitherto with this kind of lenses and boasting 4 aspherical elements, one extra low chromatic dispersion Super UD and one of very low chromatic dispersion UD, along with a top-tier mechanical construction.

It means in practice a major milestone: to have been able to overcome with a zoom lens (featuring a extreme superangular coverage up to 11 mm) the greatly forefather of all the retrofocus ultra wideangle 15 mm and 14 mm primes throughout more than 40 years: the rectilinear 13 elements in 12 groups Carl Zeiss Distagon 15 mm f/3.5 (designed and optimized for f/5.6 by the genius Erhard Glatzel, pioneer in the use of big size aspherical elements in this kind of extreme wideangle lenses boasting excellent correction of distortion and great values of resolving power and contrast) and introduced during the Photokina 1972 as prototypes HFT Distagon 15 mm f/3.5 with Rollei bayonet mount for Rolleiflex SL35 camera and as SMC Takumar 15 mm f/3.5 with M42 screwmount for Pentax cameras and manufactured for Asahi Optical Co by Carl Zeiss through an agreement between both firms.

As a matter of fact, the Carl Zeiss Distagon T* 15 mm f/3.5 C/Y in Contax / Yashica mount introduced during eighties (featuring Erhardt Glatzel ADN and identical optical formula as the 13 elements in 12 groups Carl Zeiss Distagon 15 mm f/3.5 from 1972, though with better anti-reflective multicoatings) goes on being one of the best retilinear extreme wideangle fixed lenses, and in spite of having been designed for 24 x 36 mm format film reflex cameras, it gets a spendid image quality and lack of distortion connected through an adaptor to 24 x 36 mm full frame 24 megapixel digital reflex cameras like the EOS 5D Mark III, although with professional digital 50 megapizel reflex cameras like the Canon 5DS and 5DS R its performance is not at the same level.

The Canon 11-24 mm f/4L — created right from the start for 50 megapixel 24 x 36 mm sensor — exhibits a better control of flare thanks to logically much more evolutioned and efficient multicoatings (though the anti-reflective T* coating of Erhardt Glatzel´s original Carl Zeiss Distagon 15 mm f/3.5 interacting with the large non aspherical front lens of this objective and the much smaller and thicker antepenultimate (11) aspherical element of its optical formula, but with the difference that the degree of external curvature of the Canon 11-24 mm f/4L aspherical element 2 is much larger than the non aspherical lens 2 of the Carl Zeiss Distagon 15 mm f/3.5 and much smaller (roughly half) the distance between that aspherical element 2 and the more forward huge aspherical element.
Evidently, the two reference-class lenses in the ultra angular scope designed for 24 x 36 mm format keep on nowadays being two manual focusing ones and also created for full frame:

a) The Super-Elmarit-R 15 mm f/2.8 ASPH featuring 13 elements (one of them — the second one after the large front lens — aspherical, four of anomalous partial dispersion and six made with highly refractive optical glass — ) in 10 groups, designed by Schneider-Kreuznach following Leica specifications and introduced in 2001, virtually without any flare and delivering extraordinary levels of resolution and contrast at full aperture in center, border and corners, as well as an impressive correction of distortion, practically integral elimination of the color fringing and astigmatism and a minimum focusing distance of only 18 cm, with exceedingly reduced dimensions of 85,3 mm length and 83,5 mm diameter in its widest area, along with a weight of 710 g.

b) The Carl Zeiss Distagon 15 mm f/2.8 T* launched into market in 2012, featuring 15 elements of them aspherical ) in 12 groups, a minimum focusing distance of 25 cm, dimensions of 132 mm length x 103 mm diameter, weight of 748 g, and in the same way as the Super-Elmarit-R 15 mm f/2.8 ASPH boasting extraordinary values in every relevant optical aspect, even at widest f/2.8 aperture, even slightly beating the Super-Elmarit-R 15 mm f/2.8, in addition to likewise boasting a first-class mechanical construction.

These two primes play in another league (particularly the Zeiss Distagon 15 mm f/2.8 T*, albeit the Super-Elmarit-R 15 mm f/2.8 ASPH approaches it very much in performance, which is very commendable, because it is an eleven years older lens but much smaller and light, with almost 5 cm less in length and 38 g less in weight, so it was more difficult to design and manufacture, and both of them are the flagships in the field of extreme superwideangle lenses for 24 x 36 mm format, but with an inevitably steep price: between 6,000 and 7,000 euros the Super-Elmarit-R 15 mm f/2.8 ASPH (which is also a coveted collector´s item, because only 420 units were made) in the second hand market and around 2,700 euros the Carl Zeiss Distagon 15 mm f/2.8 T* new, since the entirely metallic construction of both of them, their sturdiness and duration in time, the top quality of the noble metals used in their making, the exquisite brass focusing helicals, the precision of the mechanical engineering they include, their lineal resolution and contrast, their correction of distortion and absence of chromatic aberrations makeing possible to get indoor pictures in environments with great contrasts of high and low lights or bright reflections, and many other qualities, are currently unsurpassed.

But the arrival of digital photography and the need to adapt optical designs to digital sensors which have replaced the chemical emulsions, has brought about between 2007 with the introduction of the Nikkor 14-24 mm f/2.8G ED and the 2015 with the launching into market of the Canon 11-24 mm f/4L

a milepost in the history of photographic lenses broadly speaking and of the variable focal length ones in particular: the creation of zoom lenses designed for 24 x 36 m format with first-string optical and mechanical performance regarding resolution, contrast, correction of distortion, lack of aberrations and stretching of the most angular coverage up to the 14 mm in a first stage and uncommonly up to the 11 mm with the recent Canon 11-24 mm f/2.8L which position both zooms in an image quality location between the original Carl Zeiss Distagon 15 mm f/3.5 created by Erhard Glatzel in 1972 — and which was the yardstick until the end of XX Century — and the unbeatable duo Super-Elmarit-R 15 mm f/3.5 ASPH / Carl Zeiss Distagon 15 mm f/2.8 T*.

And to do this with zoom lenses is an unprecedented opto-mechanical feat, whose main characters have been firstly the Nikkor 14-24 mm f/2.8G ED and now this amazing Canon 11-24 mm f/4L.