09-04-2010, 09:45 PM
[quote name='Brightcolours' timestamp='1283621528' post='2487']
Golly, you are right. Both in case of the 1st surface being 30% reflective and the 2nd surface being 30% reflective, the same amount of ghost light will exit the mirror. In both cases the light (and ghost light) are only "filtered" (refected 30% up) once.
[/quote]
Actually, it does matter in the case of light reflected of the sensor back to the mirror, because most of that light would not take part in any reflections and hence possible ghosting. Also, the reflections of the non-mirror coated surface are always going to be a lot less in intensity than anything reflected by the mirror, as the transmission intensity from an optical POV is always going to be stronger unless you get very close to the angle where complete reflection takes place. However, in that case the angle is going to be so steep, that there is no way it can still get back to the other side of the mirror, when reflecting again of the other side of the glass/air transition, so to speak. After all, angle of incidence = angle of exit, in the case of reflection. On the second surface the angle of incidence is determined by the angle of the incident light on the first surface and the refractive index of the glass.
Kind regards, Wim
Golly, you are right. Both in case of the 1st surface being 30% reflective and the 2nd surface being 30% reflective, the same amount of ghost light will exit the mirror. In both cases the light (and ghost light) are only "filtered" (refected 30% up) once.
[/quote]
Actually, it does matter in the case of light reflected of the sensor back to the mirror, because most of that light would not take part in any reflections and hence possible ghosting. Also, the reflections of the non-mirror coated surface are always going to be a lot less in intensity than anything reflected by the mirror, as the transmission intensity from an optical POV is always going to be stronger unless you get very close to the angle where complete reflection takes place. However, in that case the angle is going to be so steep, that there is no way it can still get back to the other side of the mirror, when reflecting again of the other side of the glass/air transition, so to speak. After all, angle of incidence = angle of exit, in the case of reflection. On the second surface the angle of incidence is determined by the angle of the incident light on the first surface and the refractive index of the glass.
Kind regards, Wim
Gear: Canon EOS R with 3 primes and 2 zooms, 4 EF-R adapters, Canon EOS 5 (analog), 9 Canon EF primes, a lone Canon EF zoom, 2 extenders, 2 converters, tubes; Olympus OM-D 1 Mk II & Pen F with 12 primes, 6 zooms, and 3 Metabones EF-MFT adapters ....