Topic: The magnificently modified Canon FL 28mm project
I don't know why, I still want to play. Maybe it's the ego of having "Canon" lenses on a Canon body. Anyhow, I noticed that at least some of the older Canon manual (FL, not FD) mount lenses had the aperture mechanism on the front ring, and had no second lever. I traded a 28mm lens for a bellows I had, and went to work.
First, no modification to the inner lens group is necessary, except to cut off the aperture lever in the rear. The entire inner lens group comes out by removing one nut/retainer on the rear.
I thought this over for about a day.
THIS CAN BE PERFORMED WITH NO LATHE. Only files, or a Dremel type grinder, a couple of small screwdrivers, and normal hand tools are needed.
I haven't decided whether to drill and tap the parts for assembly, whether to solder the adapter to the body ring, epoxy, etc.
I used a Nikon-to-Canon import adapter, which is brass, and is two piece. I removed the front piece, and will only use the rear as a mount, which makes it thinner.
Here's the pieces out of the lens which will be used. The upper left is the "inner lens group, which is held in place by the nut just behind. The screwdriver is pointing to a hole in the black section from which a screw is removed. This "keyed" the lens group to hold it from rotating, but will not be used. The inner group will not index at the original rotation. Left center is the "inner body" which holds the lens group, and is unmodified. Left lower is the focus control ring, screwed to the focus helix. Lower center is the main body. Lower right is the original Canon retainer, which will be used as part of the mount. Center right is the rear section of the Nikon-to Canon adapter The little brass piece is originally a stop for the focus mechanism. It turns out that it sticks out enough next to the aperture mechanism in front, that it interferes with allowing the lens group to screw "back" far enough, and simply will not be used.:
First step is to remove the bayonet lugs from the original ring--the one you operate to install/remove the lens from the camera. Again, you could file or grind this. Remove the bayonet lugs, out to the "major" ID of the ring:
Next is to cut the shoulder to a larger ID on the rear of the body, so the lens group can come back further for infinity. Again, you can do this with files or a grinder:
Here's a picture with the inner section stuck into the main outer body ring BACKWARDS, just to show how we now have clearance:
Below illustrates the focus helix, removed from the outer control ring. Originally Canon used round head screws, which interfered with allowing the inner section to screw back in far enough for infinity. I simply countersunk the original holes, and used flathead screws. THESE SCREWS came from the dissasembly of the Nikon adapter, which is two-piece.
Also, to gain just a little more, I discovered the focus threads are a double thread, that is, you can start the helix in the body in either of two places 180deg apart. By re-installing the outer focus control ring in the "wrong" spot, and playing with this thread, I gained another tiny amount "back" into the body for infinity Below shows the focus control ring re-installed on the helix, with the countersunk screws--which originally came on the Nikon adapter.
Here are the modified pieces, getting closer. Top left is a "first" Nikon-to-Canon adapter, which I ruined. I was trying to turn off the two ridges on the face, which may not even be necessary. To the right is the "second" Nikon adapter, rear section. To the right yet is the Canon retainer, after removing the bayonet lugs. Top far right is the inner lens group.
Lower left is the main body, to it's right is the modified focus ring, and right further is the retaining nut for the lens group. The washer will NOT be used as it adds yet another tiny bit of "back" distance for infinity. To the far right is the inner body, unmodified
Below shows how the modified retainer ring will fit onto the body. I may just epoxy this, as the two have threads and other ledges which will "catch" I also may get some screws and a tap and screw it together
Here's how the mount, the retainer, and the lens body would fit. I might solder or screw the mount to the retainer, and then epoxy the retainer to the body. The two just happened to be the right size to fit
Once that's all done, assembly should progress easily. Install the focus ring, and screw all the way in, then back out to the inf. mark. Screw in the inner housing, and then install the lens group. The "play" here is, that you must screw it in as far as can be, without binding the aperture control ring on the front. This becomes your maximum "back" position. At that point, I'd have to install an index screw(s) to hold the inner group from turning as you focus. Finally, loosen the inner lens group (rear) retainer nut, and rotate so the aperture markings are "up."
Tomorrow, I'll try and check for inf. focus, and see if I can drum up some no "0" or no. "1" machine screws and a tap.
Last edited by 440roadrunner (2008-01-11 05:55:06)