Іван Циба wrote: > Which light sources have no UV in their spectrum? Something like an incandescent illuminant through normal glass should have low UV. Many fluorescent lights have relatively low UV. Incandescent lights (particularly QI) without some sort of UV filter have medium levels of UV. Some discharge lamps and sunlight have higher relative levels of UV. > And instrument without UV filter give correct measurement results when > paper have fluorescent components and it viewed in light that have UV, or > when paper have no brightener and it viewed in any lighting conditions? Ideally the instrument light should exactly match the intended viewing illuminant with regard to the relative UV content. This is difficult to arrange in practice, hence things like FWA compensation <http://www.argyllcms.com/doc/colprof.html#f> and illuminant measurement <http://www.argyllcms.com/doc/illumread.html> Graeme Gill.