We have at least one physicist who specialises in this area. He knows good deal about light and optics. I'm rather rusty in this area. But you can be sure that UV does not pass through camera lenses. What UV filters are supposed to do is remove a large part of the shorter wave violet light that would mess up colour balance at high altitudes and around the seashore -- maybe the desert as well.
We discussed this matter long ago. I suggested that light of *shortish* wavelengths might be converted, after passing through some of the glass, into light of a longer wavelength; and that it might be this changed light that caused the problems. But at the time I thought this was a bit far-fetched. I could go on but perhaps we should wait for our expert to notice the thread? Don _______________ Dr E D F Williams http://personal.inet.fi/cool/don.williams Author's Web Site and Photo Gallery See New Pages 'The Cement Company from HELL!' Updated: August 15, 2003 "Oh my God! They've killed Teddy!" ----- Original Message ----- From: "Cotty" <[EMAIL PROTECTED]> To: "pentax list" <[EMAIL PROTECTED]> Sent: Tuesday, November 11, 2003 8:34 PM Subject: Re: How to tell clear glass from UV glass? > On 11/11/03, [EMAIL PROTECTED] disgorged: > > >The UV that passes clear glass (and gets through camera lenses) is rather > >long wave -- just the other side of visible. Short-wave UV is stopped by > >most glass. To pass short wave UV, optics made of quartz are needed. When we > >talk about UV in photography we really mean violet light. My guess is that > >light of wavelength below than 240 nm would be stopped by ordinary glass. > >Anything below 200 nm is shortwave UV. These are arbitrary boundaries and > >someone is sure to disagree. And there are bound to be big differences > >between lenses. We have an expert in the group perhaps he'll tell us? > > *and you're not* ?? > > <thud> > > > > > Cheers, > Cotty > > > ___/\__ > || (O) | People, Places, Pastiche > ||=====| www.macads.co.uk/snaps > _____________________________ > Free UK Mac Ads www.macads.co.uk >
