Fortunately this is a very easy “fix” and just about anybody can perform the modification with patience and a steady hand. Using a Dremel tool with a sanding disk or cutting wheel, gently sand the fin down by ~1mm. The fin is ridged; one ridge should be enough. The fin does not have to removed, just reduced a little.

The metal is very soft and the modification only takes a minute or two. Be sure to cover rear lens opening with painters tape or something similar to keep the metal shavings from falling into the lens. In the picture above, the fin has been ground even with focus confirmation chip. After the fin has been modified, a black Sharpie marker can be used to touch-up the brass metal. When complete most people would not know the lens has been modified.

The metal fin does not effect the 100mm Planar’s operation or performance. The metal fin is there to protect the aperture actuator when the lens is set down on a table without the rear lens attached. With fin shaved, the 100mm Planar will still work on Contax film body SLRs. after the fin has been reduced (or removed), do take care not damage or bend the aperture actuator in normal day to day use.

The metal fin protects the aperture actuator and plays no role in the lens’ operation. Thus shaving (reducing) the fin has no negative consequences mechanically. That said, purists and collectors may balk at the modification. Most of the Contax 100mm Planars are not in museum quality condition anyway, so I do not see any harm. For somebody who collects lenses, they may view this modification as a negative, so it could hurt the resale value. I have bought and sold several 100’s and it has not been a problem for me.The image to the left shows the fin path as the lens is mounted on a Canon dSLR. Most likely the fin will rub along the plastic starting at about the 4:00 o’clock position. As fin continues along its path, it may get stuck on the raised plastic block (Canon 1Ds Mark II shown). Finally it could strike the gold contacts.

In my experience the Cameraquest, Kindai, DSLR-Exchange and HappyPageHK adapters all worked without issue and each has reached infinity focus. Currently I use a HappyPageHK Auto Focus Confirmation adapter. All the focus points work with the focus confirmation adapter, so off-axis compositions are simpler.

Since switching to a focus confirmation adapter, my keeper rate has increased significantly. I HIGHLY RECOMMEND them with the Canon 1-series. I have also tried the HappyPageHK adapter on the Canon 40D and Canon 5D dSLRs. Focus confirmation worked fine on both lenses, but the metering is hit or miss. My HappyPageHK adapter is one if the first HappyPageHK focus confirmation adapters (as of May 2008 I be ordering a new adapter from HappyPageHK when he has stock again). I am not sure why the metering varies on the Canon 5D and Canon 40D, but others have noted the same.  More information on adapters here. Or, you can post questions & comments in the new Forums section.

ADDITIONAL IMAGES BELOW

The six product pictures are of a Contax 100m Planar F2.0 MM lens with a HappyPageHK focus confirmation attached. A new gallery has been added (next page) which has a wide array of images taken with the Canon 1Ds, Canon 1Ds Mark II and Canon 1Ds Mark III during the past 4 years.