Cemented Faces Repaired, Carl Zeiss Mirotar 8/500 T* 鏡片膠合異常

2023/9

Over the past few years, I have often purchased second-hand lenses from Yahoo Auctions Japan. The main reasons are the wide selection and reasonable prices (the depreciation of the Japanese yen is also a factor). Of course, there have been quite a few cases of stumbling upon lemons. Minor issues like loose parts leading to the aperture not opening or small patches of spiderweb-like mold are still relatively easy to deal with.

This time, I hit a major snag. The purchase price of this lens was about sixty percent of the market price, and as soon as I received it, I was startled by the droplet-shaped reflections on the reflective mirror elements. It didn't look like mold, and I suspected it might be due to the silver coating on the reflective mirror cracking. It seemed unlikely to be salvageable, but I decided to give it a shot and consulted a professional technician.

I made an appointment with the technician, and upon inspection, he determined that the poor adhesion between lens elements was causing the issue. There are two lens surfaces on this lens that need to be bonded with special glue. The previous repair technician probably didn't bond them properly, causing air bubbles in the adhesive, resulting in marks resembling water droplets.

這幾年常常從日本Yahoo拍賣購買二手鏡頭，主要是選擇多，價格合理(日幣貶值也是因素之一)，當然踩到地雷的案例也不少，小問題像是零件鬆脫導致光圈無法開啟、小範圍蜘蛛網狀霉絲都還容易處理。

這次算是採到大地雷，這顆鏡頭的購入價約是市價的六成，拿到手後第一時間就被反射鏡組上反射的水滴狀影像嚇到，看起來不像霉絲，自己判定可能是反光鏡的鏡面塗銀層龜裂，很可能沒救了，不過還是死馬當活馬醫吧，找專業的師傅看看吧。

跟師傅約了時間，師傅看了一下就判定這是鏡組間黏合不佳，這鏡頭有兩處鏡片接觸面須用專用膠黏合，前一位修鏡師傅應該沒黏好了，導致黏膠間產生氣泡，形成類似水滴狀的痕跡。



Water droplets in Front View
鏡頭正面水滴狀脫膠



Water droplets in Rear View
鏡頭背面水滴狀脫膠



The technician explained that if it were old factory lenses, heating the lens group after applying adhesive could separate them. If it was a more recent adhesive, such as UV glue, it would require soaking in a solvent solution to separate them. Two weeks later, the technician returned the lens to me, now clean and pristine, explaining that the lens group was separated after soaking in the solvent and then re-bonded after cleaning.


修鏡師傅表示如果是舊的原廠鏡片黏合膠應該加熱後鏡組就可分離，如果是必較近期的黏合可能是用UV膠，需要泡溶劑藥水才可分離。兩週後，師傅交還給我乾淨漂亮的鏡頭，並說明是泡溶劑後分離鏡組，清潔後再重新黏合。






The lens after repair
經修復後的鏡頭

Carl Zeiss Mirotar 8/500 T*
Cemented Face 膠合面示意圖