----- Original Message ----- From: "Joseph Chamberlain, DDS : I have always been skeptical about using lenses (specially : the more expensive ones) without a filter as protection. But in this : particular case I just might have to open an exception. lenses are precision tools, and they have limitations in form and function. Wide angles, albeit rectilinear are fast approaching fish eye focal lengths these days and many have such a wide angle that filtration wide open is just not possible - maybe you have one of these lenses. don't forget there are a raft of other lens designs that don't handle front filters too well for various reasons - like fisheyes, catadioptrics, microscope lenses fitted for macro work, pinholes, flash-incorporated medical lenses.. they're simply not designed to accommodate front filtration. I've never been a fan of having a filter on to just be there all the time in the off chance the lens might take a thump. Any additional glass in front of the lens elements adds more reflective surfaces to degrade the image and thus potentially increases flare and lowers resolution - having said that I threw my backpack on a couple of summers back not noticing a pocket was open and a rather expensive lens hit the ground with a sound thump, accompanied by an explosion of plastic and glass shards. Once the dust settled I found I'd last used that lens with a 1A filter which was still on the lens, and it and the lens cap had borne the brunt of the fall, shattering but leaving the front lens element undamaged :-) k
