Nikon F and F2 Extension Tubes


Quick and easy extension explanation: when I say X1:X2, I mean that X1 is the feature size on the film, and X2 is the physical feature size, e.g. 1:3 implies that an object that is 30mm long will be reproduced as an image 10mm long on film.

Another way of expressing this is through the [mag ratio], which is the magnification ratio in use, i.e.

a picture taken at 1:2 has a [mag ratio] = 0.5
a picture taken at 1:1 has a [mag ratio] = 1.0
a picture taken at 2:1 has a [mag ratio] = 2.0, etc.

It is easy to determine the [mag ratio] for a given lens (used in normal, unreversed position) and a set amount of extension. Without any extension in the lens's focussing helical,

[mag ratio] = (amount of added extension)/(lens's focal length)

It's useful to know that bellows factor gives

(effective aperture) = (set aperture)*(1 + [mag ratio])

when calculating what the effect of your tube on the scene you're trying to meter.

Original Extension Ring Set (A, B1, B2, C, D)

A
female F-Bayonet
male F-Bayonet
5.8mm extension
B1
female thread
male F-Bayonet
5.0mm extension
B2
female F-Bayonet
male thread
5.8mm extension
C
female thread
male thread
10mm extension
D
female thread
male thread
20mm extension

  • lens + A + body == 5.8mm extension
  • lens + B2 + B1 + body == 10.8mm extension
  • lens + B2 + B1 + A + body == 16.6mm extension
  • lens + B2 + C + B1 + body == 20.8mm extension
  • lens + B2 + C + B1 + A + body == 26.6mm extension
  • lens + B2 + D + B1 + body == 30.8mm extension
  • lens + B2 + D + B1 + A + body == 36.6mm extension
  • lens + B2 + C + D + B1 + body == 40.8mm extension
  • lens + B2 + C + D + B1 + A + body == 46.6mm extension

This was an early version of the Extension Ring Set K, and shares its features and drawbacks.

Extension Ring Set K

K1
female F-Bayonet
male F-Bayonet
5.8mm extension
K2
female thread
male F-Bayonet
5.0mm extension
K3
female F-Bayonet
male thread
5.8mm extension
K4
female thread
male thread
10mm extension
K5
female thread
male thread
20mm extension

This consists of five tubes, fairly logically named K1, K2, K3, K4, and K5. They are not meter-coupled. They do not preserve the automatic diaphragm. They are fairly versatile, and offer a generous range of extension, even if they are a bit fiddly. Only the A tube may be used without combining with any of the others. On each of the other tubes, the "male thread" will mate with the "female thread" and so, in combination, offer the following extensions:

  • lens + K1 + body == 5.8mm extension
  • lens + K3 + K2 + body == 10.8mm extension
  • lens + K3 + K2 + K1 + body == 16.6mm extension
  • lens + K3 + K4 + K2 + body == 20.8mm extension
  • lens + K3 + K4 + K2 + K1 + body == 26.6mm extension
  • lens + K3 + K5 + K2 + body == 30.8mm extension
  • lens + K3 + K5 + K2 + K1 + body == 36.6mm extension
  • lens + K3 + K4 + K5 + K2 + body == 40.8mm extension
  • lens + K3 + K4 + K5 + K2 + K1 + body == 46.6mm extension

Nikon's Comments: The [...] versatile Extension Ring Set K consists of five rings which are used individually or in various combinations to get a variety of magnifications. The rings can be used with any lens from 20mm to 300mm. The set comes in a leather case.

E Semiauto Extension Ring

female F-Bayonet
male F-Bayonet
14mm extension
plunger-operated diaphragm coupling
not meter coupled

I'm not sure how this is different than the E2 -- perhaps it is a remake on the order of the M to M2 ring. At any rate, you can also use this ring when a lens is reversed on bellows to provide for a semi-automatic diaphragm without the extra cost/bulk of a dual-cable release.

E2 Semiauto Extension Ring

female F-Bayonet
male F-Bayonet
14mm extension
plunger-operated diaphragm coupling
not meter coupled

Nikon's Comments: The E2 Ring adds an extension of 14mm to the lens and has a built-in plunger that is pressed to open the lens diaphragm to full aperture for bright viewing and focussing. Releasing the plunger stops down the lens to taking aperture.

M Ring

female F-Bayonet
male F-Bayonet
27.5mm extension
automatic diaphragm coupling
not meter coupled

This is the tube matched with the 55mm auto-diaphragm macros; when added to them, it provides continuous focussing from 1:2 to 1:1. The first version has the effective aperture etched on it, for a lens with no helical extension.

M2 Ring

female F-Bayonet
male F-Bayonet
27.5mm extension
automatic diaphragm coupling
not meter coupled

This is the tube matched with the 55mm auto-diaphragm macros; when added to them, it provides continuous focussing from 1:2 to 1:1.

Extension Tube PK-1

female F-Bayonet
male F-Bayonet
8mm extension
automatic diaphragm coupling
non-AI meter coupled

This is a nice little tube which is more convenient to use than the K1 or A rings because it retains both aperture and meter coupling. On the other hand, it doesn't offer quite as short an extension as the K1 and will damage AI cameras without a flip-up lever (Nikkormat FT3, FE, FM, F3, F4, F5 with modification).

Extension Tube PK-2

female F-Bayonet
male F-Bayonet
14mm extension
automatic diaphragm coupling
non-AI meter coupled

This tube offers the same amount of extension as the older E rings, but without the added plunger-diaphragm, so these are most useful for lenses mounted normally. It will damage AI cameras without a flip-up lever (Nikkormat FT3, FE, FM, F3, F4, F5 with modification).

Extension Tube PK-3

female F-Bayonet
male F-Bayonet
27.5mm extension
automatic diaphragm coupling
non-AI meter coupled

This tube offers the same amount of extension as the older M rings, and is meter-coupled, to boot. Thus, it is well-matched to 55mm auto-diaphragm Micros. However, it will damage AI cameras without a flip-up lever (Nikkormat FT3, FE, FM, F3, F4, F5 with modification).

Extension Tube PN-1

female F-Bayonet
male F-Bayonet
52.5mm extension
automatic diaphragm coupling
non-AI meter coupled
built-in rotating tripod collar

This tube is matched with the older 105f/4 Micro and offers continuous focussing (when mounted) from 1:2 to 1:1. With the 105f/4 racked out to 1:1, the entire combination is quite impressively long. With the 105f/2.8 Micro AI-S, it offers focussing slightly beyond 1:1 (because that lens shortens its focal length as you focus closer). It also has a nice rotating tripod collar which helps the mounting of the 105mm tremendously. It will damage AI cameras without a flip-up lever (Nikkormat FT3, FE, FM, F3, F4, F5 with modification).

Extension Tube PK-11

female F-Bayonet
male F-Bayonet
8mm extension
automatic diaphragm coupling
AI meter coupled

This is a nice little tube which is more convenient to use than the K1 or A rings because it retains both aperture and meter coupling. On the other hand, it doesn't offer quite as short an extension as the K1 although now it has the AI meter coupling.

Extension Tube PK-12

female F-Bayonet
male F-Bayonet
14mm extension
automatic diaphragm coupling
AI meter coupled

This tube offers the same amount of extension as the older E rings, but without the added plunger-diaphragm, so these are most useful for lenses mounted normally. Now it offers AI meter coupling.

Extension Tube PK-13

female F-Bayonet
male F-Bayonet
27.5mm extension
automatic diaphragm coupling
AI meter coupled

This tube offers the same amount of extension as the older M rings, and is meter-coupled, to boot. Thus, it is well-matched to 55mm auto-diaphragm Micros. Now it offers AI meter coupling.

Extension Tube PN-11

female F-Bayonet
male F-Bayonet
52.5mm extension
automatic diaphragm coupling
AI meter coupled
built-in rotating tripod collar

This tube is matched with the older 105f/4 Micro and offers continuous focussing (when mounted) from 1:2 to 1:1. With the 105f/4 racked out to 1:1, the entire combination is quite impressively long. With the 105f/2.8 Micro AI-S, it offers focussing slightly beyond 1:1 (because that lens shortens its focal length as you focus closer). It also has a nice rotating tripod collar which helps the mounting of the 105mm tremendously. It is now AI meter coupled.

This tube is quite favorable to use with longer IF lenses, such as the 300f/4.5 (sometimes along with the PK-13) to get a lens with unparalleled close-up working distance.

BR-1 (1a) Rangefinder Adapter Ring

female S-Bayonet
male F-Bayonet
62.3 mm extension (?)
not diaphragm coupled
not meter coupled

I am not sure if this is the same as the N-F tube used to adapt the old rangefinder telephotos (180/2.5, 250/4, 350/4.5, 500/5, 1000/6.3 reflex) to the F-bayonet mount. The N-F tube provided the appropriate amount of extension required to focus these lenses to infinity (as they'd been designed for the rangefinders' reflex housing). The BR-1 was used exclusively on the 135f/4 Bellows lens in conjunction with the Bellows 2. Since the Bellows 1 was designated for the rangefinder series (again, with the reflex housing), the BR-1 probably also provided the correct amount of extension required to focus the lens to infinity with a camera and bellows mounted. (I have heard it occasionally called the B-F tube ...)

It was later updated (along with the Bellows 2) to the BR-1a (and Bellows 2a) to be compatible with the Cordless Pack. Nikon added 3mm of extension to the rear standard of the Bellows 2 to make the 2a clear the extra bulk of the Cordless Pack, and correspondingly subtracted 3mm from the BR-1 to make the BR-1a.

BR-2 Macro Reversing Ring

male 52mm filter thread
male F-Bayonet
not diaphragm coupled
not meter coupled

This ring will mount a lens with 52mm thread in reverse on a bellows. The BR-5 is similar, but works for 62mm-threaded lenses. The BR-2 was later updated in the autofocus era so that its male F-bayonet would not interfere with the AF contacts in the body.

BR-3 Adapter Ring

female F-Bayonet
female 52mm filter thread
not diaphragm coupled
not meter coupled

This ring was originally intended for attaching the slide-copying attachments to a reversed lens, but it makes for a dandy way to fit filters to the exposed rear element of a reversed lens. Early versions are all chrome-colored, while later ones have a black plastic filter-thread piece (and a metal bayonet).

BR-4 Semiauto Diaphragm Ring

female F-Bayonet
male F-Bayonet
9mm extension
semi-automatic diaphragm coupled
not meter coupled

This ring provides for a semiautomatic diaphragm when used with Bellows units. Apparently, it is spring-loaded so that the diaphragm is held open without any pressure from one end of a double-cable release, but stops down to the appropriate aperture when the release is squeezed.

BR-6 Semiauto Diaphragm Ring

female F-Bayonet
male F-Bayonet
9mm extension
semi-automatic diaphragm coupled
not meter coupled

Apparently, this is an updated BR-4.

F-Mount EL-Nikkor Adapter

female Leica thread
male F-Bayonet

This adapter allows the Leica-threaded EL-Nikkor enlarging lenses to be mounted to the bellows units.

F-Mount EL-Nikkor Reverse Adapter

male 40.5mm? thread
male F-Bayonet

This adapter allows the Leica-threaded EL-Nikkor enlarging lenses to be mounted in reverse to the bellows units. I am not sure, but I think it is only the 50mm and 63mm EL-Nikkors (then again, Nikon made several 50mm EL-Nikkor variants ...)


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