Nikkor 10.5 mm f/2.8 fisheye:

Make it a "friendly" manual lens when adapted on a Canon EOS

Issue 31 March 2006

rev. 23 January 2007

This very good lens can be easily and mechanically adapted on the Digital (or not) Canon EOS. An example of adaptation on a Rebel XT (EOS 350D) is presented here.

But there is no aperture ring on this lens. To adjust the aperture stop setting, the Nikon camera will move the little lug that is traditionally located on the back of the lens. When it is mounted on any camera, there is then no way to manually command and adjust the stop setting externally.

The Canon EOS camera is designed to electrically command the aperture stop setting of the lens. Unlike the Nikon camera, it has no mechanical linkage to do so.

Then, inserting a little piece of plastic in the slot in which the aperture command mechanical lug moves, is the coarse but efficient current way to set the aperture stop. But this is not very friendly and this setting is often left fixed at a preset position during a whole shooting session as changing this setting is not easy to do, for example in the dark or in the middle of a walking crowd. This drawback is reported by a witness, for instance, here where Hans Nyberg writes "The big problem using the Nikkor on Canon is that it has no aperture ring. You have to fix the aperture lever by using something like a hard cardboard or plastic piece. It works fine but of course it is difficult to change it."

A modification of the adapter that allows independant and easy external control of the aperture stop setting by simply using the whole lens as an aperture ring is described here after.

Hence manual setting is possible while the camera is at eye level even in the course of a shooting session. Here is a QTVR (200kB) movie that demonstrates this. Observe my hand -on the left side of the image- that moves the lens in a short rotation in order to change setting of the aperture opening:

Installation principle

While the adapter can now be rotated on the camera (but just within the limits where the lug can move inside of the slot i.e.about 5 mm that is equivalent to about 14 Degrees of rotation range), the whole adapter could be now removed from the lens only by first unscrewing at least one of the two screws that hold the catcher blade around the lug.

After the adapter and lens assembly has been associated via the adapter and locked by the Canon EOS mount spring-actuated "click"stop pin (i.e. after 60 degrees CW rotation) onto the EOS camera, it can be moved manually by about 14 Degrees CW and then after CCW: the aperture is thus opened from largest stop setting to smallest stop setting and vice versa. The aperture is thus now externally and manually controlable.

On an APS-C sized digital sensor, this 14 Degrees rotation of the whole lens onto the camera will make the very far corner of the rectangular image getting somewhat dark for some wide aperture values as the sun shield blocks the Field of View in slanted position of the lens. This pure mechanical vignetting is very small indeed and does not at all have a real influence on the correct stitching of a 360 Degrees panorama.

Some adapters may be flawed as the thickness could be wrong. This induces focusing setting difficulties. Have a look here for a possible modification that completely correct this defect.

Furthermore, on a full frame (24x36mm) sensor (or film), the formidable angle of view that could be obtained from this excellent lens is also dramatically reduced by pure vignetting by the sunshield. (BTW, in my opinion, this was this only purpose of the shield when knowing the flare resistance of this lens).

Sawing off the sunshield is thus the way to make the lens fully operable with a full frame 35 mm camera. Note that this is not mandatory with a APS-C sensor sized EOS camera case (300D, 350D, 20D, Etc.)

Here you can see the appearence of the resulting possible combos:

Nikkor 10.5mm + EOS 20D Nikkor 10.5mm + EOS 5D

Note on the photograph that a printed sticker has been stuck around the barrel of the lens in order to provide readable indication of the aperture stop current setting.

All the Nikon lenses of any type and of any focal length and that are deprived of aperture ring could probably be adapted the same way on an EOS camera and thus providing full manual external control of the lens.

Alternate design:

Two different solutions were conceived and applied:

A- Reminder of the basic solution (see above): a narrow blade is bent to fit around the Aperture Setting Lug and is attached inside the adapter ring by means of two screws.

Alternatively, my personal favorite solution:

B- A spring blade is fixed in the inner side of the adapter ring with two teeth that catch the Aperture lug end.

Then.

(click to enlarge).

Installing and removing of the adapter is done exactly as it is done with any original adapter i.e. no tool is required and the transformation is done instantly!

The conversion is not so definitive as for the former solution.

Elephoto (aka Fotodiox PRO-series) adapter

This high-end adapter is apparently sold under either Fotodiox (PRO-series) or Elephoto brand names.

It is quite different from the type that are taken into account before in this page (BTW that is very similar to the Fotodiox consumer grade series). On the Canon side there is a integral flat ring obviously to dampen possible stray light reflexion from the sensor as its surface is striped and mate black anodized.

This feature make the modifications that were described above "almost" impossible to install (if one doesn't want to get rid of this flat ring with a file, of course).

Proposed alternate modification:

The release lever tiny mechanism which is a feature of this adapter type, can be be very easily removed with a screw driver in a first step.

Then a very simple fork can be made from a 0.2 mm thick steel sheet (see the scketch below) and screwed firmly on this flat ring to clamp the aperture setting lug:

This little fork has been tinted blak by immersion in a drop of black printer ink.

The adapter shown above is labeled as ELEPHOTO NF-EOS on its ring.

More "graphically described" and Zoomed in:

Detailed installation steps:

I had to be more explicit on the way to do this installation when responding to one of you reading that page. I then can just repeat what I have told him:

1) The little fork should be already completely machined and the 2 mm Dia hole in should have been drilled in it. In short it should be ready to be mounted.
2) The (un)locking lever-spring mechanism and the lock pin should have been dismounted from the adapter and discarded at this stage. You may keep them in a safe place if you wish.
3) Mount the adapter on the rear part of the Nikkor lens and move it until it is mechanically stopped after about CCW 60 degrees rotation as if there still was the safety lock stop installed.
4) Put the little fork around the lug and resting on the stripped side of the flat ring.
5) Push it against spring action in order to move the aperture setting little lug CCW until it is stopped by the end of the slot in the lens ass. Make sure that this is the case: if not, then move the adapter back (CW) until this is surely happening. The lug must be able to reach the end of the slot for the full aperture opening setting(< 2.8). Yes, I repeat: in fact at this position, the aperture shall be more opened than the f/2.8 Nikon specification. You just shall use all hidden manufacturer margins.
6) Then, keep everything in place (against spring action) and mark (engrave) the position of the fork hole center onto the surface of the stripped flat ring surface.
7) Drill a 1,5 mm Dia hole precisely at this marked location on the adapter after having dismounted it, of course.
8) Tap at 2 mm Dia. thread. Be careful as this is a thin aluminum piece.
9) Put everything back in place and put the little fork around the lug, resting onto the surface of the flat stripped surface. Then screw it down on this ring. Tighten the screw gently.
10) Move the adapter back and forth from one end of the lug slot to the other end (only a few degrees is possible).
11) Enjoy!

Michel Thoby

Issued 28 February 2006

Last revision: 23 January 2007: Elephoto adapter addendum