Archived posting to the Leica Users Group, 2000/07/25[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]
The coatings have to be a quarter wavelength thick so that the reflections are exactly a half a wavelength out of phase and thus cancelled out by the incoming light. Austin is, of course, referring to the width of the filter mount. John Collier >>Austin Franklin wrote: >> >> One of the advantages of the Heliopan 'Standard Coating' filters, is they >> are SO thin. I do not know if the multi-coated ones are thin also, they >> may be... > >then Shel Belinkoff enquired: > >How thin are the Heliopan coatings? B+W coatings are, according to >the B+W catalog I have here, about 1/4 wavelength (and a chart is >shown showing the wavelength in the 400nm - 700nm range). I don't >know what a "nm" is, but since we're discussing wavelengths of light, >I'd imagine it to be very small.