章魚 寫:
21mm 是一支 Float elements + IF 鏡頭。
According to my dis-asembling CZ lens experience, the most difficult to do re-alignment is : 35/1.4 > 16/2.8 > 18/4. [with floating elements]. The 180/2.8 has not been dis-asemble yet [Floating + IF], which I would avoid to dis-assemble unless there are problem with the lens.
. I think one of the reason cauing the "Softness" of this 180/2.8 Sonnar from many Contax users are the re-alignment precision of the Floating Elements, but I cannot prove it yet.
All others fixed focus lens and have no floating elements are very reliable. They can be re-assemble back to their orginal precision easily and just do the focus adjust. So far, I have dis-assembled the 25/2.8, 35/2.8, 50/1.4, 85/1.4 and 135/2.8, do some cleaning of the dust inside and the lens element in between the aperture. Then re-assemble them. Since all my lenses are bought second-hand, I used to do some cleaning (inside and outside) before I use them. The elements between the aperture is the most easily get dirt / oil vapour from the lubrician, which I think would affect the color/flare performance. Therefore, I would recommend those fixed focus lens without floating elements + IF if you really need to consider buying second hand ones. For the Floatings ones, just reverse the difficuilties of re-alignment and you should have a high chance to get a good one. For vario-zooms, I think it is more difficult and should be sent back to factory for calibration / alignment... or simply, just buy new at ManShing