SIGMA 300mm f/2.8 APO 鏡片問題處理 treatment for the problems with the lens glasses

前陣子，先後收到兩支同款鏡頭，Sigma 300mm f/2.8 APO，一支是Minolta/Sony A mount (Case 1)，一支是Nikon mount (Case 2)。
兩支的問題都是對焦鏡組的鏡片有問題。

Case 1 的是內鏡組鏡片起霧，取出鏡片後發現，有一片鏡片的兩個面都有霧，一面是一般單純的霧，簡單的清理就清乾淨；另外一面是鍍膜變質所以起的霧，只有拋光才能讓鏡片恢復乾淨通透可拍攝的狀態，在獲得主人的同意之後，便將受傷的鍍膜拋除。

Case 2是內鏡組看起來有許多奇怪的斑點，去出鏡片之後確認是膠合鏡組脫膠。經過重新黏合處理之後，問題便解決，鏡頭也恢復乾淨通透狀！

兩支都是玻璃的問題，也都順利處理完成，恭喜它們獲得重生！


Recently, I received two Sigma 300mm f/2.8 APO successively, one is Minolta/Sony A mount (Case 1)，the other is Nikon mount (Case 2).

Case 1 has internal haze. After I took apart the lens, I found that there has a lens element suffered from coating issue on both front and rear surface.
On the rear surface is normal fog, and can be cleaned away easily.
On the front surface is coating deterioration, the only way to make it clear is to polish the damaged coating. I proceed the polishing treatment after I got the owner's permission.


Case 2 has many weird spots internally. After I took the lens out, I confirmed the problem is a kind of lens group separation/balsam issue. Following the separation/re-cementing protocol I created, the lens regained it original clean and clear condition.

I'm very happy that the problems with the two lenses were resolved smoothly and completely, and congratulate to their owner!