Archived posting to the Leica Users Group, 1997/06/13
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]> > At 09:46 PM 6/12/97 -0700, Jacques Bilinski wrote: > > > >Please explain how a photon reflected from the first surface of a filter > >can possibly end up on the emulsion to 'degrade the picture'. > > > > Please read pages 87-88 in Gunter Osterloh's "Applied LEICA Technique," > Page 4 of the "B+W Filter Catalog," page 202 of the "Leica Manual, 15th >many on the www. > > Jim I already understand the physics of lens coatings. I was only asking for an explanation as to why you believe that "The first surface is indeed the most important". I believe the opposite is true. The first surface benefits the LEAST from lens coatings. This may expalin why as Mark pointed out some lenses have all surfaces EXCEPT the first surface coated. So why do modern lenses and filters have coatings on the front surface? There are 2 reasons: 1. If a filter is added to a lens, or if filters are stacked, then the first surface is no longer the first surface. 2. Less importantly there will be light reflected from a surface other than the first surface traveling towards the first surface (away from the camera). Lens coating on the first surface will minimize the amount of this light reflected back towards the film by the first surface.