I can not find this in Google search, So I write down during CLA and hope this note can help other people who want to try CLA themselves. Carl Zeiss Contax 50mmf1.4 MMJ CLA The front filter thread with the name plate will screw off by holding the lens barrel and the front part.The front group optical cells will screw off by a proper rubber ring and sheet The rear group optical cell will screw off at a whole group. If the optical cell near the aperture blades side you can clean the optical surface as well as the any oil on the blades. If the focus helical thread need re-grease or you need to total CLA this lens do the following From mount rear end, mark the position of the pin that connect the aperture coupler (from the lens it is at 11 o’clock from the lens mount side, the camera is located at 1 o’clock, when re-assembling if the position is not right it aperture will read different from f1.4, if move at the end of right side near the 12 o’clock side, it will read as f1.2, if move the left side it will read less), so mark this position, and the rings relate to each others, remove the three screws that hold the aperture coupling rings (two ring parts) Remove the four screw on he ring that hold the aperture click ring, there will be a small ball and spring under it, so be careful not lose these two small parts. Pull off the aperture ring Set at infinity mark the focus helical barrel position relate to each other Mark the two metal forks that limited the aperture blades unit from behind, two screws hold each of them, mark each metal fork position, they are little different in shape. Move the aperture blades unit out from the front (it is an alumina alloy) The critical part, the focus thread helical you have to mark the position before you take them apart, this position was adjusted at the infinite position in the factory. Move slowly marked the position when these two parts apart, after cleaning you need to put back at this position so you do not need mess up the infinite position. Clean the focus helical thread use an old tooth brush, re-grease. The assembling is in reverse order.