When you have a lens with fungus, be careful of a few things. The first is using a solvent that might get into the glue between the elements of a group. That will cause separation, and is impossible to fix. Some older coatings are not able to be cleaned completely, so will leave marks where the fungus was and cause ghosting, even if the fungus itself is completely removed. Also, some lenses had different coatings on inner surfaces than on outer ones. Unless you really know your way around lenses, it is not advisable to clean inner surfaces, as those might contain soft coatings, and taking fungus off will also remove the coating.
Generally speaking, I think it is better looking for a lens in good condition than trying to save a fungused-up one. There are exceptions, especially if the lens is valuable and salvageable, and the purchase plus repair cost is much lower than the actual value. For instance, I paid $250 for a Nikkor 85/1.4 AF D, and it cost me a further $45 to get it cleaned. More often you will find it will cost $50 to clean something that is worth $25 to start with.
Last edited by dorff; 05-08-2013 at 03:47 AM. Click to view previous post history.