CONTAX Carl Zeiss Distagon 28mm f/2.0 T* 對焦環重新潤滑 Lubricating the focusing ring

這支 Contax D28/2.0 因為對焦環轉動不順，所以送來處理。 對焦環重新潤滑算是基礎保養，不過這支鏡頭機構設計比較複雜，處理時需要多費心。
比較複雜的原因，是因為它有浮動鏡組的結構，這款鏡頭的結構透過一個對焦環來控制兩組不同螺距的對焦螺紋。它們有各自的潤滑油脂，如果要重新潤滑，不能只單獨處理一組，必須先將兩組螺紋上的油清理乾淨，再全部重新上油，確保相同的黏稠度，這樣才能達到最佳的轉動手感。
除了螺紋上游部分之外，鏡頭重新組裝最後，必須精準的校正浮動鏡組的位置，以確保邊緣畫質達到最佳化。 如果您的鏡頭是含有浮動鏡組結構，使用時光圈在f/4.0的情況下，邊緣畫質還是一糰模糊，就必須考慮送修了！

The problem with this Contax D28/2.0 is its focusing ring does not work smoothly. Focusing re-lubricating is a kind of basic maintenance, but for this lens it need to pay more attention in repairing because of its' mechanical structure is more complicated.
This lens incorporate the structure, floating lens elements, that has two sets of focusing screw thread which need to spend more time to complete the work.
In the last step in the re-assembling, the group of floating lens elements needs a precise calibration to achieve the best corner image quality.