Additional information on

Nikon (Nippon Kogaku K.K.) Prism Reflex Housing
for Nikon S-Mount telephoto lenses on Nikon Rangefinder (RF) cameras

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Introduction:- SLR displays an image through the camera's lens and eliminates common parallax errors on a typical rangefinder system esp. at close range focusing where it started to increase as the focusing distance decreases. The angle of view of a given lens also changes with distance. Overall, rangefinder focusing can be very accurate for normal to moderate wideangle photography. But at extreme both ends of the spectrum in particularly macro, duplication & long telephotography, its weakness will become apparent. Rangefinder focusing system uses a built-in bright-line frame inside the finder to aid photographer with the lens' picture angle. However, the system has physical constraints esp. when using with ultrawideangles and telephotos where the bright-line frame becomes too small. During the early days, ultrawideangle photography beyond 35mm would require a add-on Optical Finder, whereas for long telephotography beyond 135mm, none of the popular camera labels had provided a frame line inside finder due to practical reasons. Some of the newer series of rangefinder Nikon rangefinder Cameras introduced were equipped with a 28mm wideangle bright-line frame but there for telephotography beyond 13.5cm, photographers would require a Reflex Housing for focusing control. Reflex Housing is just an accessory that added between the picture taking lens and the camera body. It houses a reflex mirror. In a way, it works like a reflex camera principle but the mechanism is entirely mechanical and thus, it only offers possibility like a reflex camera. It operates via a cable release that connects to the camera and the housing, when you trip - it raises the mirror and fires away with a shot. Using a Reflex Housing indirectly adds up the distance between the lens and film plane, which also means usual lenses can also be used for close-up or macro photography. For telephotography, the reflex housing solves the, otherwise tiny frameline inside the viewfinder which may cause rangefinder misaligned or leading to incorrect focusing. As many added on magnifiers (such as right angle and even 45° angled finder with high magnification ratio etc.) were being design to provide convenience and pinpoint focusing, it had indirectly expands the rangefinder system capabilities to other applications. However, a negative aspect is, as the basic assembly only has a mirror within and it was not a complex prism finder design, so, the image is reversed.

LEICA PLOOT Reflex Housing - LINK Black body LEICA / E.Leitz Wetzlar Visoflex 1 Reflex Housing with Screw Mount - LINK Leica / E.Leitz Wetzlar Visoflex 1 Reflex Housing w/ 5X Magnifier/Finder Leica / E.Leitz Wetzlar Right Angle Magnifier for Visoflex 1 Reflex Housing  - LINK Leica / E.Leitz Wetzlar 45 Angled Magnifier Finder for Visoflex 1  - LINK


Visoflex 1 screw mount

Leica Visoflex 1 w/ 5X Magnifier

Right Angle Magnifier for Visoflex 1

45° angled Magnifier for Visoflex 1

Rangefinder bright-line framelines for various focla lengths such as 5cm, 8.5cm, 10.5cm and 13.5cm inside the viewfinder of the Nikon SP
I am not particularly sure who was the smart guy who had invented this innovative accessory for RF tele-photography. But probably it can trace back to Leica where Leitz first introduced their telephoto back in 1935. The focal length was simply too long for accurate focusing with the rangefinder. Leitz had designed a mirror reflex housing named PLOOT (Visoflex name was adopted after the war) for the purpose of focusing/framing. As some of the Leitz lenses had short mount or their lens head can be removed and permits use of universal focusing to be mount on the Visoflex and/or other accessories such as extension tubes or even bellows. The Leica Visoflex-specific lenses cover from the short Elmar 65mm to Telyt-lens group up to 800mm lenses. The Nikon's RF Nikkor lens usable with the Reflex Housing were the Nikkor 18cm f/2.5, 25cm f/4.0, 35cm f/4.5, 50cm f/5.0, Mirror-Nikkor 100cm f/6.3 as well as as Bellow-Nikkor 105mm f/4.0 (Lens Head). Other possibilities include normal lenses to be used for close-up works via increase distance between lens and film plane (works just like and extension tube, except it is a fixed size device). Unlike the Leica which can have many combinations/versions in relation to the lens mount-type, Nikon has a more straight forward system integration with their rangefinder camera/lenses. The purpose of this Section on Reflex Housing is essential to addressed first as it relates directly to other pages featuring the few long telephoto RF Nikkor lenses.

<<<--- Noted the 10.5cm / 13.5mm indicative bright-line frame inside the Nikon SP ? For lenses that goes beyond the 13.5mm, it will become very difficult to determine the focusing and other than viewing comfort, it may also lead to inaccuracy. So, the Reflex Housing comes in handy even if it adds weight and size to portability, with the additional inconvenience in reverse image projection.

Rangefinder S with bright frame line (illustration photo only) not to actual scale

Rangefinder bright frameline for Nikon 35Ti at normal 35mm

Rangefinder bright frameline for Nikon 35Ti in panorama mode

Viewfinder frameline for Nikon AF 35Ti ranegfinder camera

Comparing the viewfinder auto illuminated frameline with a modern AF rangefinder Nikon 35Ti / 28Ti (1993/ 1994) which has a fixed focal length Nikkor lens built-in. The parallax error also occurred when shooting at close range.



frameline close-up mode.gif

Rangefinder bright frameline for close-up on the Nikon 35Ti


0.4m ~10.m

Nikon Reflex Housing Type 1, 1955
Nikon (Nippon Kogaku KK) Reflex Housing Model 1
Introduced:- 195? Discontinued:- 1955/6

The Nikon Reflex Housing Model one was introduced to supplement the RF Nikkor 25cm f/4.0 telephoto lens which the conventional built-in finder frame line cannot accommodate such a long tele-focal length. In relation to its introductory date, there were some conflicting data
* but I guess around 1954 should be more precise as most other long telephoto lenses were introduced beginning from this stage. The Model 1 has a rather conservative design and it has quite a similar original Leica PLOOT model (1935~1950) where it came with a square, boxy appearance. Focusing is via a vertical magnifier and the finder is removable. I am not sure some of the older variable finder-types such as right angle finder can be fitted onto this version but according to various sources, even though the Finder has been designed with a provision for interchangeability but there was no known finder type other than the Right Angle Finder (as shown at the bottom pictures). But one known problem in its design was the screen inside the main module will not rotate when you intend to revert the camera side way for vertical format shooting. Only the main module was serialized but the removable finder was not in the Model 1. At the left hand side of the main chassis were the slide for switching the camera body for vertical shooting. An inconvenience operational design was the different location of the cable release sockets, one at the top and another at the bottom. Anyway, it was Nikon first effort for a Reflex Housing Unit and in many aspect it lagged behind the Leica such as more Magnifier options like 5X and 30X Magnifier were offered. Besides, Leica (and 3rd party makers) also has other extension of accessories such as a Micro-Mirror Reflex Housing / Novoflex for close-up / Duplication photography etc.) ; So, even though the original Nikon Reflex Housing may be considered as a commendable effort by the Japanese manufacturer, but it had some shortcomings in its overall system. However, many of which that found in the early Model 1 were being patched / upgraded in the Model 2 that appeared in 1956.

Nikon (Nippon Kogaku KK) Reflex Housing Model One (Type 1) Nikon (Nippon Kogaku KK) Reflex Housing Model One (Type 1)  inverted view

Mr. Robert Rotoloni, author of Nikon Rangefinder Camera had suggested in his journal that the Model 1 bear serial number from 371000~371190, which makes this early Model I Unit less than 200 units were being produced.

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Comparing Nikon Reflex Housing type/model 1 & 2

Nikon (Nippon Kogaku KK) Reflex Housing Model 2
Introduced:- 1956 Discontinued:- 1963/4

The next update for the Nikon reflex Housing was introduced in 1956. It was a complete redesign and in many ways it was a radical change with a smooth, round corner design. Further, Nikon has also designed a couple of Finder / Magnifier that center around the Model 2 to increase its operational ease. Further, the exterior finishing has been changed to a crinkle finish which in a way has helped to project a rugged and rigid look and feel. Incidentally, this update also has some similar exterior finishing like the Leica Visoflex 1 Model (1951~1956) that introduced after the original PLOOT effort (refer to the
top of this page). Unlike the previous right angle finder, the model 2 was supplied with a 45 degrees Finder which angled for the photographer to take easier view. Besides, the Finder has a 4X Magnifier within for pinpoint focusing. The previous vertical Finder was replaced with an 90° Finder prism as optional piece. There were two other major improvement in this version. Firstly, the focusing screen is now be changed to rotate when the camera body is tilt vertically. Secondly, both the mirror raised mechanism and shutter release cable socket were placed at one side which add up to its ease of use. Further, the timing is adjustable and the standard release can also be replaceable for other application such as when use the camera for macro and duplicating / copy works. The Model 2 have two sets of serial number for the main module as well as the finder.

Viewfinder on Nikon Reflex Housing Type 2
NOTE:- Many of the system accessories would require the Reflex Housing for ease of photo composition and/or precise focusing. As the nature of rangefinder could pose difficulties especially when working at close focuses. In a way, mounting the housing also increase the lens to film plane distance in affecting magnification. One acccessory that works particularly well with the housing is the use of short mount lens (such as Nikkor-Q 1:4 f=13.5cm Bellow-Nikkor) with Nikon Bellow Focusing Device, it enables magnification up to even 1:1. At such close distance and high magnification, the reflex housing provides a more accurate view than depending on guess work or manual calculation via camera rangfinder. Other combinations such for repro-copy etc. would find the Reflex Housing also is an indispensible tool, so the housing is not entirely to be used only for long tele-Nikkor lenses only.

Nikon (Nippon Kogaku KK) Reflex Housing Model One (Type 1) Nikon (Nippon Kogaku KK) Reflex Housing Model One (Type 1)  inverted view Nikon (Nippon Kogaku KK) Reflex Housing Model One (Type 1)  inverted view
Nikon 90 prism for rangefinder acccessory, reflex housing type 2
The alternate 90° Right Angle prism has a rather oversized prism head component. When mounted onto the Reflex Housing, it works something like a SLR type of eye-level finder. Could have been designed like the Leica Right Angle Finder for the Visoflex 1 which is more compact and handy.

In general, the Nikon RF Reflex Housing Model 2 was a far improved finder than model 1. It was designed to supplement the Nikon and the long focus lenses such as 180mm, 250mm, 500mm and 1000mm reflex Mirror lens. The housing was also required as a component with the Nikon Bellow Focusing Attachment unit. It may be added between the top stage of the Nikon Repro Copy Outfit, Model S and the Nikon RF body to add approx. 74mm of extension for larger image size on the film with the Repro Copy Outfit for a direct accurate view during focusing.

Nikon Reflex Housing Model / Type 2 with  25cm f4 and cable releases /lens hoods
The front and the rear bayonet mounts are used in a conventional way to fit a Nikon and the lens. Just match the red index dot and will lock the various components in place or for detaching. You may adjust the eyepiece of the 4.3X Magnifier on to the image erecting prism until the small circle on the ground glass is sharp or clear. The prism / Finder, as mentioned earlier, is removable from the main console via turning counter clockwise rotation in the bayonet mount.

<<<---- An excellent picture of the Model 2 with other RF Nikkor long telephoto lenses

Nikon Reflex Housing Model 2 with lens attached seeijng through the tube
I am not good nor a historian on RF Nikon/Nikkor, so it has to fall back to Guru when it relates to other information. Again, Mr. Robert Rotoloni, author of Nikon Rangefinder Camera had suggested in his journal that the Model 2 main console may bear serial number from 471000 onwards to 471763. S/N for the 45° Angle Finder : 67000 ~67628; while the 90° Angle Finder:- 77000~77032.

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Nikon Reflex Housing Model/Type 2 front view Nikon Reflex Housing Model/Type 2 side section view


Nikon RF Lens Finder Group

Nikon RF variframe / varifocal Finder Group

Nikon RF Sports Finder Group

Nikon RF Lens hood Group

Nikon RF Reflex Housing for Telephoto lens Group

Nikon RF close-up accessories Group Nikon RF automatic film advance devices (motor drive/winder) Group

Nikon RF Lens misselenous accessories Group

Fixed fens Finders


Sports Finder

Lens Hoods

Reflex Housing


Motor Drive




Fixed Focal length Finders | Variframe / Varifocal / Sports Finders | Reflex Housing | Motor Drive | Close-ups | Nikon RF Flash System
Accessories: Lens caps, Hoods/shades, Cases/Compartments, Filters, Packing/boxes, & Others | Instruction Manuals | Original Price Lists


Nikon RF lens group:-
2.1cm f/4.0 (21mm) | 2.5cm f/4.0 (25mm) | 2.8cm f/3.5 (28mm) | 3.5cm (35mm) lens group | 5cm (50mm) lens group
Micro-Nikkor 50mm f/3.5 | 8.5cm (85mm) lens group | 10.5cm (105mm) lens group | 13.5cm lens group
18cm f/2.5 (180mm) | 25cm f/4.0 (250mm) | 35cm f/4.5 (350mm) | 50cm f/5.0 (500mm) | 100cm f/6.3 (external Link)

Nikon Rangefinder (RF) Models | Pictorial History of Nikon | A small visual library on Nikon Ultra-Micro-Nikkor lenses
Manual Focus Nikkor lenses | Autofocus Nikkor lenses

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Credit:- Co-developed with my friend, Rick_Oleson. THANKS to all the contributors in the form of images/pictures as well as content which made up the basis of this RF Nikkor site. Image(s) copyright © 2008. All rights reserved. Please respect the visual property of the contributing photographer. 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 contributions from surfers who claimed originality of their work for educational purposes. The creator of the site will not be responsible for any discrepancies that may arise from dispute except rectifying them after verification."Nikon", "Nikkormat", "Nippon Kokagu KK" & "Nikkor" are registered trade names of Nikon Corporation Inc., Japan. Site made with an Apple G5 IMac.