TenEleven
Well-known
The head bartender nicknamed the Canon 28mm f3.5 lens for Contax mount the "Cantax", quite catchy. So, I guess taking a Contax lens and using a Canon shell to put it into LTM could thus be called reverse "Cantax".
I happened upon a very cheap (~$45) Canon 50/1.5 that I picked up on a whim. Sadly it had the Canon glass disease quite badly and no amount of cleaning and even polishing would help. In the flashlight test the rear triplet lit up like a disco and the images the lens made in anything but the most subdued light could be described as impressionistic.
A couple of months later I picked up a Contax mount collapsible Sonnar which had likely seen a nasty fall. Most likely lens first with the lens extended. The "nose" was bent and the lens had a totally broken collapsing mechanism, with two of the prongs sheared clean off. I offered the seller ~$90 and he accepted. Originally the plan was to harvest the glass out of the destroyed mount and put it in a black and nickel lens.
However to my chagrin the transfer to the Nickel lens failed due to different front element diameters. Also, drop damage and oily aperture aside the lens was in such good condition that it seemed a shame to break it apart.
Plan B: Try put in another rear mounting claw onto the lens. However, the screw holes were located such that I would have to drill one hole right on top of the next - which would make rather questionable structural integrity. In the collapsible Sonnar design the lens is more or less suspended from the rear claw.
Thus - Plan C: Following Brians guides I shortened the Sonnars focal length from ~52.3mm to 51.7mm by filing down the lens housing and moving in the rear triplet by about ~0.1mm. I discarded the totally destroyed rear "claw" section and kept the rest of the lens, giving it a good clean and doweling out the impact points.
Then I removed the lens from the Canon lens, put it in a safe place for parts and renovated the focus mount as much as possible. After everything was back together I filed out the part the lens rides on in the Canon focus mount. This had to be done as the "throat" of the Canon lens is very narrow and I kept the Sonnar in its original Barrel sans mount part.
I stuck everything together and cut a very fine spacer out of a sheet of copper to retain the lens into the mount. I also filed down and then fitted the replacement "claw" sans screw back. The filing was done so that the "claws" wouldn't create friction against the rotating RF cam. With this arrangement the individual prongs of the claw end up pressing against the rolled copper tube making for a secure fit holding the lens snugly in place. No glue needed. Since the original baffling would not fit - I blackened out the rangefinder cam with matte black paint. You can see all that below:
I also made a slight modification to the Canon focus stopper mechanism allowing for slightly closer focus making sure that my LTM cameras can still focus. I chose the last point before they disengaged. I guess it was a sliver under 85cm or 2.8'.
I love how closely the knurling of Zeiss and Canon matches.
After that I aligned the aperture dot to the focus indicator on the Canon and re-indexed the Sonnars aperture to follow. And with that I was done.
I ended up filling the bald spots in the name-ring with black and white paint - also thanks to careful doweling the lens now accepts filters and hoods as usual. Since all the parts are brass or glass the lens is small but rather dense and heavy.
247g or 8.71oz a rather hefty little fellow. I hope you liked this excursion of "lens hacking" - I'm sorry that I don't have taken any pictures of the "guts" but I was too busy measuring and filing before I even considered making this post. But I have a hunch this won't be the last lens I do like this and I shall take more pictures for the next one.
I happened upon a very cheap (~$45) Canon 50/1.5 that I picked up on a whim. Sadly it had the Canon glass disease quite badly and no amount of cleaning and even polishing would help. In the flashlight test the rear triplet lit up like a disco and the images the lens made in anything but the most subdued light could be described as impressionistic.
A couple of months later I picked up a Contax mount collapsible Sonnar which had likely seen a nasty fall. Most likely lens first with the lens extended. The "nose" was bent and the lens had a totally broken collapsing mechanism, with two of the prongs sheared clean off. I offered the seller ~$90 and he accepted. Originally the plan was to harvest the glass out of the destroyed mount and put it in a black and nickel lens.
However to my chagrin the transfer to the Nickel lens failed due to different front element diameters. Also, drop damage and oily aperture aside the lens was in such good condition that it seemed a shame to break it apart.
Plan B: Try put in another rear mounting claw onto the lens. However, the screw holes were located such that I would have to drill one hole right on top of the next - which would make rather questionable structural integrity. In the collapsible Sonnar design the lens is more or less suspended from the rear claw.
Thus - Plan C: Following Brians guides I shortened the Sonnars focal length from ~52.3mm to 51.7mm by filing down the lens housing and moving in the rear triplet by about ~0.1mm. I discarded the totally destroyed rear "claw" section and kept the rest of the lens, giving it a good clean and doweling out the impact points.
Then I removed the lens from the Canon lens, put it in a safe place for parts and renovated the focus mount as much as possible. After everything was back together I filed out the part the lens rides on in the Canon focus mount. This had to be done as the "throat" of the Canon lens is very narrow and I kept the Sonnar in its original Barrel sans mount part.
I stuck everything together and cut a very fine spacer out of a sheet of copper to retain the lens into the mount. I also filed down and then fitted the replacement "claw" sans screw back. The filing was done so that the "claws" wouldn't create friction against the rotating RF cam. With this arrangement the individual prongs of the claw end up pressing against the rolled copper tube making for a secure fit holding the lens snugly in place. No glue needed. Since the original baffling would not fit - I blackened out the rangefinder cam with matte black paint. You can see all that below:
I also made a slight modification to the Canon focus stopper mechanism allowing for slightly closer focus making sure that my LTM cameras can still focus. I chose the last point before they disengaged. I guess it was a sliver under 85cm or 2.8'.
I love how closely the knurling of Zeiss and Canon matches.
After that I aligned the aperture dot to the focus indicator on the Canon and re-indexed the Sonnars aperture to follow. And with that I was done.
I ended up filling the bald spots in the name-ring with black and white paint - also thanks to careful doweling the lens now accepts filters and hoods as usual. Since all the parts are brass or glass the lens is small but rather dense and heavy.
247g or 8.71oz a rather hefty little fellow. I hope you liked this excursion of "lens hacking" - I'm sorry that I don't have taken any pictures of the "guts" but I was too busy measuring and filing before I even considered making this post. But I have a hunch this won't be the last lens I do like this and I shall take more pictures for the next one.
