First, dont be put off by Nikons disclaimers (both Fujifilm and Kodak endorse user cleaning if done properly). The Lithium Niobate filter over the D1 and D100 CCDs is somewhat difficult to scratch if you use the right tools (on the MHOS Scale of Hardness table that ranges from talc at 0 to diamond at 10, Lithium Niobate is a 5, the same as Apatite, and a bit lower than Orthoclase and Quartz; Fujifilm and Kodak don't identify the material they use [nor does Nikon on the later cameras], but it seems just as durable). While it's possible to scratch the filter surface, it's also not at all easy to do if you're using the right tools.