LEICA SUMMICRON-M 28mm f/2.0 ASPH. 對焦環潤滑 Lubricating the focus ring/helicoids

這支M28/2.0 ASPH. 的對焦環轉動手感有點鬆，某些區段不是很順暢，來回轉動會有遲滯感，也有點鏡身鬆動不穩的現象。

這問題可能的兩個因素～

1. 對焦螺紋的潤滑油脂本體可能因油水分離 變薄了，比較稀的液態油脂在鏡身鏡筒內任意流動或揮發，留在螺紋裡的固態油脂不夠飽滿，無法充分填滿螺紋間隙，使得對焦環來回轉動有遲滯感以及鏡身鬆動不穩
2. 兩組螺紋內的油脂油水分離程度不同，各自支撐力不同，在兩組螺紋間互相牽引時，會造成某些區段轉動不順暢

處理的方法，必須先將兩組螺紋完整清潔乾淨，鏡身鏡筒上不必要的液態油脂也要清潔乾淨，之後再以穩定的潤滑油脂平均潤滑兩組螺紋，組裝後再確認手感柔順。

The focus ring of this M28/2.0 ASPH. works a little bit stiff and sluggish. The lens body also has a little bit loose.

These problems may caused by the condition of the grease itself. The body of the grease became thinner which may result from grease's oil separation.

The way to resolve the problem is to clean the focus helicoids completely, and apply a stable grease to the helicoids to make sure the focus ring works smoothly after re-assembling.