Additional information on

Nikon (Nippon Kogaku K.K.) RF W-Nikkor.C 1:4 f=2.5cm (25mm f/4.0)
ultra-wideangle lens for Nikon S-Mount Rangefinder cameras


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Carl Zeiss Jena Toppogon 21mm f/4.0 lens
A brief background on the German version:- Topogon design has a double Gauss optical arrangement. It was first introduced by Dr. Robert Richter back in 1933 by modifying the Hypergon (1900, Goerz) by adding a pair of concave elements to the Hypergon design (comprised of two convex meniscus elements that have the same radius of curvature.) without disturbing the symmetrical configuration of the lens system and delivering the objective of correcting longitudinal chromatic aberration and spherical aberration. Due to the optical nature with a high resolving power and optical characteristic in excellent flatness of field, low distortion and curvature of field, all these which added to its wide angle coverage; thus, Topogon design was often pursued by army in its development during the World War II for surveillance aerial photography and other special application to spy on enemy locations/formation. During post war period, East German Carl Zeiss Jena saw the potential of the design and began commercialized the 2.5cm lens for 35mm photography back in 1950. Nippon Kogaku, on the other hand, was also believed to have been exploring practical usage of the Topogon lens type for the Imperial Army where its research effort was put to commercial application after the war. The Zeiss version was marked T* coated but the production for this lens by Zeiss Jena was only lasted for a few years. Based on some references, less than 700 units of the Zeiss 2.5cm Topogon were being produced by Zeiss Jena between 1950~1953.

<<<--- LINK to image profile of Carl Zeiss JENA TOPOGON 25mm f/4.0
   
Strangely, the Zeiss version of the 2.5cm ultrawide had NOT been designed with any dedicated accessory finder along as standard accessory. But rather, owners of the Zeiss Topogon lens had to use the Zeiss Turret Finder. Neither any of the available contarex camera has built-in bright-line frame for such an extensive wideangle coverage, so the use of the Turret is essential for practical shooting sequence. It was learnt that Nippon Kogaku K.K. was already began selling a version of the 2.5cm f/4.0 lens in a similar Topogon design to other camera labels during or post war era.

German Carl Zeiss Jena 440 Turret finder German Zeiss Ikon 440 Turret finder
Shown are the Carl Zeiss Jena Turret 440 Finder and Zeiss Ikon's 440 Turret. The Zeiss Jena Turret has a 2.8cm marking while the latter has provision for an even wider range at 25mm, 35, 50, 85 and 135mm settings / focal lengths.

Credit:- Image courtesy of Mr. Mike Otto® <staff@pacificrimcamera.com> URL: Pacific Rim Camera, who also operates a popular Ebay Store. Image Copyright © 2003. All rights reserved. Pacific Rim camera can also be reached by mail to: Pacific Rim Camera 1965 Davcor St SE Salem, OR 97302 (503) 370-7461 Fax number is (503) 370-8801. Please respect the visual property of the contributing photographer.

Carl Zeiss Jena Toppogon 21mm f/4.0 lens Nikon's W-Nikkor.C 25mm f/4.0 Screw mount (SM) ultra-wideangle lens with  dedicated accessory Finder
A visual comparison between a Nippon Kogaku K.K. early Screw Mount 2.5cm f/4.0 and Carl Zeiss Jena's 2.5cm Topogon ultrawide.

Credit: Image of the Carl Zeiss Jena Topogon at the far left courtesy of Photo Arsenal Worldwide® Germany. The Company also maintains an active EBAY Store, trading many used and new photo equipment of various labels. Photo Arsenal can be contacted via ebayshop @ arsenal-photo.com. Image(s) copyright © 2008. All rights reserved. Please respect the visual property of the contributing photographer.

Basic information on Nikon (Nippon Kogaku K.K.) W-Nikkor.C 1:4 f=2.5cm M39 Screw-Mount (SM*) ultra-wideangle lens
Year Introduced: June of 1955 (Nikon stated date. Other sources it was available earlier)

So, there is actually two versions of the Nippon Kogaku K.K. (Nikon) W.Nikkor 1:4 f=2.5cm ultra-wideangle lens. The older version which bear a Leica M39 Screw-mount (SM) and many people thought Nikon had this Nikkor wide made for many other camera labels such as Leica, Nicca, Tower and even on the Canon RF models earlier than offficial released date. The old SM version has a much lighter weight and a more compact dimension than the Nikon Bayonet mount version introduced later. The old lens was believed to have been supplied in all chrome finish. The most noticeable visual between the two is, the SM version comes with the distance scales engraved in black on the large metal ring (closest to the camera body).

Leica Screw Mount (LSM) W.Nikkor 2.5cm 1:4 wideagle lens Leica Screw Mount at the rear section of  (LSM) W.Nikkor 2.5cm 1:4 wideagle lens
Credit: All images courtesy of Mr. Kenneth Frey from his Ebay Store Image Copyright © 2008. All rights reserved. Please respect the visual property of the contributing photographer.
   
The distance scales are actually printed at the front as well as at rear section of the ring. Depth of field scales can be read at the metal lens barrel at the middle lens barrel. All the scales are marked in feet and no meters scales were provided in this version. Unlike the Zeiss Jena counterpart, Nikon own was supplied with a dedicated accessory optical finder that has a rounded metal front section with a rectangular lens diaphragm outline. The rear/center portion of the finder has a black finish. There is another circular metal frame rounding the eyepiece at he back with "Nippon Kogaku, Japan" printed circularly around the eyepiece. A "2.5" is printed at the top of the finder. All the known version of the finder for 2.5cm which surfaced in the used equipment market so far have not seen to be serialized. The photo shown at the left hand side shows a few of the various accessories. which include original Nippon Kogaku KK lens cap, Finder, adapter/lens shade for Series 6 filters as well as the leather lens case.
   
Full accessories for Nikon 25mm f/4.0 SM mount ultra-wide Beutifully taken photo of the 2.5cm Nikkor Wideangle with dedicated Optical Finder and accessories
   


" .... I've had a lot of fun with it, but my interests are changing so time to let it go. I used it mostly with a Canon VI-L, Canon 7, and a Minolta 35 that I painted black that this lens looked really cool on - not to mention that it produced some great images for me. Only 950 of these were made in Leica screwmount compared to almost 2000 in Nikon mount, so these are a bit tough to find these days. I have owned the Nikon mt. version and I must say I prefer the screwmount version to actually use for a couple reasons. Number one the lens hood screws on instead of the flimsy feeling bayonet hood on the Nikon that always felt like it was about to fall off. Also the apertures are easier to change on this lens, the outer ring rotates instead of having to reach inside the lens and slide that hard to get ahold of little tab on the Nikon. Finally there is an actual focusing knob on this one compared to the wheel focus only Nikon version. Like the Nikon version this one is amazingly small and compact, a real joy to use. The glass is clean and clear, no scratches, haze, or fungus. Looking super close there may be a couple tiny, tiny internal dust specks, but they are almost impossible to even see - the lens really in beautiful optical condition. The aperture blades works nice and smooth over the full range. Focus action is also very smooth, not too loose, not too tight. Only very light external wear. Comes with correct two piece lens shade and filter holder, I think it takes series 6 filters, it is either series 6 or 7, I think it is 6 but I forget, if you really want to know email me and I will go dig out a filter to see which one it is. Also comes with the 2.5cm finder marked L on the bottom for Leica. the finder is in very nice shape, with clean and clear optics. Also included is a Nikon front cap, sorry I do not have the rear cap for the lens. Also a Nikon round leather case is included. Another nice thing about this lens is that it is rangefinder coupled, unlike the Voigtlander 25mm which is not. The lens is a four element design, almost symmetrical, with extreme curvature to the outer elements, really must have been a tough lens to manufacture back in the fifties. Just a beautiful and rare lens, a lot of fun, especially since there are so many cameras that you can use this lens on. ...." -
Kenneth Frey -

The SM version of the 2.5 RF Nikkor lens has a minimum focusing distance at approx. 1m (3.3ft). A non-colored Infrared compensation index is provided next to the focusing index. And when rotating the aperture, the index that located at the front section around the slight recessed circle near the lens element will also change accordingly. The aperture ranges of this SM version 2.5cm Nikkor lens ranges from f/4.0 to a minimum f/22 with a 6-f-stops setting for wider depth of field control option. In comparison, the Zeiss Jena 25mm f/4.0 Topogon has a more moderate, less appealing f/16 minimum aperture. It was not known when the SM version was discontinued. But after Nikon had introduced their own rangefinder Nikon in 1948, their emphasis was refocused to develop their own bayonet version.
Various system accessories for Leica Screw Mount (LSM) W.Nikkor 2.5cm 1:4 wideagle lens
* If you still find the few versions mentioned here a little confusing. Wikipedia explained some relations: " .. The Leica screw-mount ("SM" also known as M39) cameras developed for lens manufacturer Leitz Wetzlar by Oscar Barnack; Contax cameras manufactured for Carl Zeiss Optics by camera subsidiary Zeiss-Ikon and, after Germany's defeat in World War II, produced again and then developed as the Ukrainian Kiev), Nikon S-series cameras from 1951-1962 (with design inspired by the Contax and function by the Leica), and Leica M-series cameras..".. Here shown the different versions which includes a Leica thread SM version.

Credit: All images courtesy of Mr. Kenneth Frey from his Ebay Store Image Copyright © 2008. All rights reserved.

Next:- Co-Moderator for the MIR's Lens Message Board, Robert G. Middleton also had explained ".. The M39 designation is used for a screw mount for camera lenses. It is what some people call the old screw thread Leica mount, used on the rangefinder models prior to the release of the M mount models. Technically the 39mm diameter thread used on the pre M series Leicas, should not be designated M39 - This designation is for a thread with BOTH a metric diameter and METRIC pitch. The 39mm thread, as used by Leitz had an Imperial or INCH pitch - this anomaly arose because the RMS thread specifications were the norm at that time for optical instruments. RMS was an imperial or inch standard. All Leica copies use the true M39 designation thread - except perhaps some very early FEDS, which were a direct copy of the Leica 1. In practise however, the difference in thread pitch does not stop Leica lenses fitting on the copies and Russian lenses fitting on the Leicas. Only in rare cases, when machining tolerances come into play, will you find trouble in mating a Leica Screw Mount item with a M39 mount item. ..." - Robert Glenn Middleton <(the_redd_groyne@hotmail.co.uk) -

Front view of a M39 Leica SM Mount W-Nikkor.C 1:4 f=2.5cm lens

Rear section view of a M39 Leica SM W-Nikkor.C 1:4 f=2.5cm lens with Nippon Kogaku lens cap

Credit:- Image courtesy of Mr. Darrryl Schaeffer from DS camera @ EBAY <contact:- dscamera @ aol.com>. Image Copyright © 2008. All rights reserved. Please respect the visual property of the contributing photographer.

Leica M39 LSM version of the Nippon Kogaku KK / Nikon's W.NIKKOR.C 1:4 f=2.5cm telephoto lens
comparing LEICA and NIKON models in the Nikon Rangefinder 25mm f/4
Credit: Image courtesy of Mr. Peter Coeln from LEICA Shop®, Austria who also operates a popular Westlicht Auction House. Image Copyright © 2008. All rights reserved. Please respect the visual property of the contributing photographer.

Nikon (Nippon Kogaku K.K.) W-Nikkor.C 1:4 f=2.5cm (25mm f/4.0) S-Mount (Bayonet) ultra-wideangle lens
Introduced: March, 1955#; Discontinued: August, 1969

The RF W.Nikkor 1:4 f=2.5cm ultrawide which designed specifically in Nikon own bayonet mount was first being marketed in November, 1953. After its official debut, it was once regarded as the widest lens available for Nikon RF system until the release of another Nikkor-O 1:4 f=2.1cm (21mm F/4.0) in 1959 which gave a span of difference in 6 years for another new ultra-wideangle dimension for RF Photography. The 2.5cm Nikkor lens was actually being introduced barely a year after the 1952's W-Nikkor 1:3.5 f=2.8cm wideangle. Which means to say, the 25mm RF Nikkor has remained as the only choice wider than 28mm during that era. Unlike the earlier featured Leica SM version, the bayonet mount version has quite a different physical appearance, as well as operational sequence for shooting. Due to the unique lens design of a symmetrical optical formula, which attributes to its exceptional flatness of field and minimal vigetting, it has indirectly contributes to its extremely compact design. In fact, when the lens is mounted onto a Nikon RF body, and when you view it side way, the physical extension of the lens is just only a few centimeters protruding outwards from the lens mount/camera body. # Nikon stated date in their official web site. Other sources: Both Nikon Hand Book / Nikon RF illustrated History suggested 11.1953

Side view of S-mount Bayonet type W-Nikkor.C 1:4 f=2.5cm lens photo provided by gokelvin camera@EBAY.com Nikon old rangefinder lens 25mm f/4.0 in S-mount by adorama.com

Credit: Image at the left courtesy of Mr. Kelvin LI from his popular gokelvincameras@Ebay Store which retails for many hard-to-find Nikon, canon, Contax oldies. The front view of the Nikkor-W 2.5cm f/4.0 above courtesy of "Ebay - Mathew Duren" URL: Adorama.com, who also operates a popular Ebay Store. Image Copyright © 2003. All rights reserved.

You don't find a conventional aperture ring on the lens, instead you have to manually hand set the f-stop via a slide/dial (see below) inside the slightly recessed front section of the lens. On the other hand, focusing is via a sharp edged wheel/dial. It was not entirely a good design in this respect as when the lens is mounted, there is little space for control. Equally you don't find a traditional located focusing ring on the lens barrel for easy visual when shooting or determining the focusing range. I guess Nikon optical engineers probably had put up a lot of thought to accommodate the adoption of its simple optical design and fitted with a mechanical outfit which has resulted in such a compact ultrawideangle lens to be realized.

S-mount of the Nikkor RF 2.5cm f/4.0 (25mm f/4.0) by Nikon S-Magazine
However, from a practical stand point, I might not agree the lens is a very friendly tool for shooting. For an example, you may have to tilt your camera upward just to change/check aperture and focusing distance. Although the tiny front exposed lens element is deeply recessed at the front, but still - photographer has to be extremely cautious during making shooting adjustments. As none of the prevailing Nikon RF models have a built-in bright-line frame for its extensive picture coverage, so, focusing is via manually by estimation of distance with depth of field control. The DOF scales are not printed on the top so, you also have to tilt the camera upwards to check all the settings. Thus, this can be considered as rather awkward to use if responsive shooting action is required.

<<<--- Shown here is an older, original chrome ring version. Difficult to locate such a lens now but I have found a picture via the Nikon RF magazine. For other views refer to the suggestive links below.

Based on records and various sources, there are actually TWO bayonet-mount versions available throughout its entire production cycle. The early model (1953) has a solid and rigid all chrome on brass construction (refer to the 2nd picture (B) below); it was revised after 1956 onwards with a black version (the one shown a few main paragraphs used or simply refer to the third photo (C) below). The black version is significantly lighter, weighing only 2.5oz as compared to the chrome/brass model which weighs almost 1X heavier at 4.5oz (approx. 128g).NOTE: The Black Version: Released in July, 1956, lens barrel was changed from chrome-plated brass to black light alloy in line with other lenses to standardize the outlook design.

I have been trying to locate some pictures to let you take a look how the Leica SM mount 2.5cm Nikkor-W (A) and Nikon's own S-mount when mounted onto a RF Nikon body. The Japan Nikon Kenkyukai Tokyo had a Christmas gathering back in 2004 where members had presented such a combination. Take a VISIT for the original pictures along with many other rare RF Nikon bodies/lenses.

A deeply recessed front section of the S-mount W-Nikkor 2.5 Cm lens
NOTE:- While I am not trying to pick on a lens designed 50 years ago but there are just simply too many confusing numeric printed within the tiny circular area that surrounding the lens element which comprised of three circles of printed numbers/data, aperture settings from f/4.0 ~ f/16; with the depth of field scales opposite (along with a red (R) infra compensation index. The outer circle is printed with various distance scales. The outer ring is encircled with "Nippon Kogaku, Japan" with Serial Number and the lens data "W-Nikkor.C 1:4 f=2.5cm" at the opposite. Come to think of it, size of lens data/S/N/Company name are far more prominent than the practical, frequently used figures/numbers engraved/printed for photography - well, like it or don't, I don't call all these a very friendly arrangement.

<
<<--- just take a look at the few photos displayed here with the confusing state and you will agree with me that these areas were not well handled.
The distance scales and front lens element of the 25mm f/4.0 old Nikkor RF lens The aperture setting and scales  scales and front lens element of the 25mm f/4.0 old Nikkor RF lens
Credit: All images courtesy of Mr. Kelvin from his popular gokelvin -cameras @Ebay Store Image Copyright © 2003. All rights reserved.

Nikon's optical design / construction used in the 2.5cm f/4.0 Nikkor-w ultra-wideangle lens for older series of Nikon Rangefinder cameras
Supplementary Info:- The re-engineering task of the S-mount version of the W.Nikkor 2.5cm f/4.0 was believed to be headed by a Nikon optical designer, Mr. Hideo Azuma. | Here is an interesting article | prepared by Mr. SATO, Haruo which was originally written for Nikon Club. It has addressed many technical aspect in designing and implementation of the 2.5cm Nikkor during actual production. As explained in Sato's article, despite it was a commissioned assignment by his Company to replicate the German designing concept for a workable solution for a Nikkor-W; one significant achievement by Mr. Hideo Azuma was his achievement in overcoming a shortcoming found in the Zeiss version esp. around the vignetting factor. In comparison, Mr. H. Azuma had improved the Nikkor lens brightness around the edge of the image field, ensuring evenness on the outer most periphery.

* Incidentally, Hideo Azuma was the mentor to more famous another Nikon lens designer, WAKIMOTO, Zenji who had developed the famous RF Nikkor-O 2.1cm f/4.0 ultra-wideangle lens, the early Micro-Nikkor as well as the special IC-inspection Ultra-Micro-Nikkor lens group.

With a wide angle of view (80.5° (50° x 70° well, the lens may mean nothing if it is measured by modern standard, but you have to understand, it was really "something" half a century ago..citing the fact that the first ultrawide in reflex version with a different retrofocus design for MF Nikkor 24mm (meaning - NO Mirror-Lock-Up is required when used with any reflex Nikon SLRs and permits direct viewing and metering) was only being developed in 1967). This RF Nikkor wideangle lens offers an unusually wide perspective of 25mm for the Nikon rangefinder bodies. It delivers excellent flatness of field due to use of the unique symmetrical design as well as containing vignetting to a minimal level. Some references said the W-Nikkor had used rare earth glass in its optical composition which enables common aberrations to be controlled to enable realization of such an extreme picture angle yet be able in such a remarkable compact lens package. I am not sure if the series were all being coated but most of the versions that had surfaced over the last few years are carried with a W-Nikkor.C inscription after the lens data (Well, to be honest, for the last few years - I had been very patience to wait and gather pictures/photos at Ebay (esp. by various frequent contributors to MIR site), which in anticipation one day, I will create a site on RF Nikkor here).

Nikon rangefinder version of the 2.5cm f/4.0 (25mm f/4.0) ultrawide angle lens with chrome lens mounting index marked   Nikon rangefinder version of the 2.5cm f/4.0 (25mm f/4.0) ultrawide angle lens with chrome lens mounting ring

Rear section of the lens element for the Nippon Kogaku K.K. (Nikon) rangefinder version of the 2.5cm f/4.0

Lens hood Series VII for Nikkor RF 25mm f/4.0
The W.Nikkor 2.5cm f/4.0 has many following as a collectible piece among RF Nikon enthusiasts. This was probably due to its rich background and rarity (where many Nikon historian believed only approx. 2,500 units of this unique RF Nikkor ultrawide has been produced so far.

<<<--- Rear section of the deeply recessed exposed lens element and dedicated lens hood (series VII) for the 25mm f/4.0 RF Nikkor.
Lens hood and Series VII filter for RF Nikkor 2.5cm f/4.0 Lens hood and Series VII filter for RF Nikkor 2.5cm f/4.0 lens data Lens hood and Series VII filter for RF Nikkor 2.5cm f/4.0 place of produce (japan)
Optical finder and SM Leica version fo the W.Nikkor 2.5cm f/4.0 (25mm)
To collectors who may find the Nikkor-W 2.1cm 1:4 even more difficult to find (or too pricey to own), this compromised 2.5cm RF ultrawide Nikkor can probably be a very good alternate. The lens was supplied with a matching companion Optical Finder. As none of the Nikon RF rangefinder camera system accessories such as Sports Finder or Variframe Finder had built-in provision for 25mm to aid photo composition. So, this Finder is indispensable for the lens in photography. It is a high quality optical finder. The top/rear section of the finder is marked with 2.5cm marking and has an almost similar appearance/design with the 2.1cm equivalent.

<<<--- A Nikkor RF 2.5cm in Leica SM with matching finder, I guess the the finder is interchangeable between SM and Bayonet versions where it looks as if both share a common flat base plate mounting plate).

Nikon Optical Finder for 2.5cm Wideagle lens
Use of separate optical finder requires focusing via conventional depth of field /distance estimating method (This lens is similar to the 2.1cm - where accurate focusing is not essential as long as it is within range, other than its closest focusing distance where one has to take note, but clever use of depth of field manipulation should yield adequate range of sharp focus zone. Further, by combining mid aperture in this ultrawide, it enables quick pre-focus shooting. Well, as none of the original old series of RF Nikon models provide TTL metering and thus, user may has to make use incident light meter or use experience to counter for metering. Well, Nikon did produced an own labeled exposure meter. However not all RF Nikon can make use of it as It was only being introduced after the Nikon SP (1957) because SP was the first RF Nikon that offers a non rotating shutter speed dial which enables the exposure meter be coupled onto camera. NOTE: Canon has this similar change of the non rotaing shuter speed dial a year later than the Nikon with the Canon VI-L model in 1958.

Optical Finder for Nikon's Rangefinder (RF) Nikkor 2.5cm f/4.0 (25mm f/4.0) top view with 2.5 marked Optical Finder for Nikon's Rangefinder (RF) Nikkor 2.5cm f/4.0 (25mm f/4.0) section side view

Optical Finder for Nikon's Rangefinder (RF) Nikkor 2.5cm f/4.0 (25mm f/4.0) rear optical eyepiece view Optical Finder for Nikon's Rangefinder (RF) Nikkor 2.5cm f/4.0 (25mm f/4.0) front section view with rectangular optical element Optical Finder for Nikon's Rangefinder (RF) Nikkor 2.5cm f/4.0 (25mm f/4.0) base view with flat baed metal mounting plate
Credit: All images (lens hood, Optical Finder and rear/side views above) herein courtesy of Mr. Kelvin from his popular gokelvincameras@Ebay Store which retails for many hard-to-find Nikon, canon, Contax oldies. All images Copyright © 2008. All rights reserved.

Nikon rangefinder W-Nikkor.C 1:4 f=2.5cm (25mm f/4.0) wideangle lens
Along with the 2.1cm (21mm) ultrawide and 25cm (250mm) telephoto lenses; this 2.5cm Nikkor-W has remained as the only ODD fixed focal length Nikkor lens that you can find within the decades of produce in their ever growing Nikkor lens group. Well, after the Reflex Nikon F was officially announced in 1959, Nikon first offered reflex Nikon photographers with a non Ai version of the MF Nikkor 24mm in 1967. Over the years, the popular manual focus 24mm lens group had gone through many phases of lens updating program which was directly inline with the corresponding development of metering system in the Nikon SLR camera system. The autofocus version of the 24mm (Ai-S/1985 and AF-D/1993) was among the original series of autofocus lenses being introduced with the first* integrated autofocus Nikon camera body (Nikon F501 / N2020). The W.Nikkor 1:4 f=2.5cm ultra-wideangle lens which had served many Nikon RF users throughout the years, captured history, recording major events/happenings in the world via their Nikon, has remained itself as a highly collectible optical imaging tools to all Nikon enthusiasts worldwide today.
Metal lens cap, lens hood and optical finder for Nikon rangefinder 35mm f/4 wideangle lens
* NOTE:- The first Autofocus Nikon that went on commercial production was the Nikon F3AF (1983) but most people referred it as a "prototype" which being produced to test the market. It has no full system accessories built around the camera. Unlike the F501/N2020 which began with a new evolution in the AF-Nikkor lens family for all Nikon AF bodies that followed, only two dedicated F3AF Nikkor lenses were being offered thus far; thus we still referred the Nikon F501/N2020 as the first Nikon AF SLR model.

Canon's optical design illustration of the RF 25mm f/3.5 Canon RF lens 25mm f/3.5 Canon RF lens 25mm f/3.5
SUPPLEMENTARY INFO:- It is also interesting to note that Canon also had followed Nikon's path by introducing a version of the Canon Rangefinder version of a (RF) 25mm f/3.5 lens a few years later in 1956. The Canon RF wideangle lens was also adopting the Toppogon lens type. However, Canon's version has improved it with a faster maximum lens speed than the contemporary Zeiss / Nippon Kogaku design by coming out late. Besides, it has separate aperture, focusing rings just like a normal lens. (see illustrations at the left).



Basic Specification for W-Nikkor-C 1:4 f=2.5cm wideangle lens:-

Bsic standard accesories for a LSM W-Nikkor.C 1:4 f=2.5cm lens (25mm f/4.0 RF Nikkor)
Lens Mount: Nikon S-mount for Nikon RF models or early M39 Screw Mount
Focal Length: 25mm (2.5cm)
Picture Angle: 80.5
° (50° x 70° ); Lens Coating: Single Layer
Maximum / Minimum Aperture: f/4.0 ~ f/22; Diaphragm: Manual
Optical Construction: 4 elements in 4 groups
("Topogon" Type)
Minimum Focusing Distance: 91cm (3 ft) ~
OO
Filter Attachment Size: Series VII (43mm); Hood: 47.9mm screw-in type
Dimension:-
55.8 mm dia. x 31.8 mm long (overall)
Weight (body only)
: approx. 126g (4.25oz) for Chrome version; 2.5oz (Black); Screw Mount (Leica Thread):- approx. 3-3/16 oz (75g)

Standard Accessories
: Optical Finder (2.5cm model); special rear lens cap. Optional: Screw-in type lens cap / Lens hood 34.5mm, optical filters Series VII for S-Mount; Series VI for Leica SM etc. F-S/S-F mount adapters: no info.

Other Information
: Two major versions in either Leica thread M39 Screw mount or S-Mount for Nikon RF models (Chrome 1954 and Black (1956) version). Bayonet System to mount lens cap and the Series VII lens hood. Serial Numbering used:- Chrome/Brass S-Mount starts from 402500 ~ 403500. Lighter weight black ring version up to 405000. Total:- Approx. 2,500 Units. Ref: Robert Rotoloni's An Illustrated History on Nikon Rangefinder camera.
Credit: Image(s) courtesy of Mr David Schorer® who also operates a popular Rhona45th@EBAY STORE. Image Copyright © 2008. All rights reserved. Please respect the visual property of the contributing photographer.




Depth of Field tables for W.Nikkor 1:4 f=2.5cm ultra wideangle lens
<<<--- Depth of Field tables (183k Jpeg) for W.Nikkor 1:4.0 f=2.5cm ultrawideangle lens

Recommended External Web Resources on this 2.5cm f/4.0 RF W.Nikkor:- Camera/lens development of Nikon/Nikkor lenses (Nikon Japan); Discussion Forum at Nikon Historical Society (NHS) Discussion Forum; many good pictures of the lens featured at Nikon Society (Kenkyukai), Tokyo, Japan; Zeiss TOPOGON 25mm f/4 featured at Stephen Gandy / Cameraquest as well as a featured article of the Nikkor 25mm f/4.0; An archive of useful data prepared by Frank Mechelhoff; SP5-World, Japan - excellent source on many RF Nikon/Nikkor (Japanese/English); Another lovely site with many pictures taken with a Leica SM mount Nikkor.W lens (in Japanese)

W-Nikkor-O 1:4 f=2.1cm | W-Nikkor.C 1:4 f=2.5cm | W-Nikkor.C 1:3.5 f= 2.8cm | W-Nikkor.C 3.5cm lens Group (3.5/2.5/1.8) | Stereo-Nikkor 1:3.5 f=3.5cm | 5cm (50mm) lens group | RF Micro-Nikkor 1:3.5 f=5cm | Nikkor-P.C 1:2 f=8.5cm lens group / Nikkor-S.C 1:1.5 f=8.5cm lens group | Nikkor-P.C 1:2.5 f=10.5cm lens group / Nikkor-T 1:4 f=10.5cm | Nikkor-Q.C 13.5cm lens group: 135/4, 135/3.5 Early / Last Version, 135/4 Bellow lens | Nikkor-H 1:2.5 f=18cm | Nikkor-Q 1:4 f=25cm | Nikkor-T 1:4.5 f=35cm | Nikkor-T.C 1:5 f=50cm | Reflex-Nikkor 100cm f/6.3

System Accessories for Nikon Rangefinder cameras
Optical Finders (4 parts):-
Fixed Focal length Finders (index page): 2.1cm, 2.5cm, 2.8cm, 3.5cm, 35cm Stereo, 5cm, 8.5cm, 10.5cm, 13.5cm | Variframe / Varifocal / Sport-frames | Nikon Reflex Housing

Nikon S36/S72/S250 Motor Drives / S36 Manual | light meters | Nikon RF Flash/Speedlights | Close-up photography / Repro Copy Outfit / Nikon Bellow Focusing Device (in progress) | Cases/Compartments | Lens & body caps, Lens Hoods/shades, Original Price Lists | packaging/boxes

Instruction Manuals

Related info:- Main index page for Leica/Leitz | Contax/Carl Zeiss | Seiki Kogaku (Canon)

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Credit:- Special thanks to all the contributors of images and content which made up the basis of the site. Note:certain content and images appeared in this site were either scanned from official marketing leaflets, brochures, sales manuals or publications published by Nikon over the years and/or contribution from surfers who claimed originality of their work for educational purposes. The creator of the site will not be responsible for may discrepancies arise from such dispute except rectifying them after verification."Nikon", "Nikkormat", "Nippon Kokagu KK" & "Nikkor" are registered trade name of Nikon Corporation Inc., Japan. Site made with an Apple G5 IMac.