09-03-2010, 10:08 PM
I think that makes sense.
Looking at it another way, any light ray hitting the mirror that is not perpendicular to the mirror will be refracted to some other non-perpendicular angle. It doesn't matter what that is exactly, but internal reflections will occur and could provide additional light paths offset from the main image. The level of that would be significantly reduced, but this is similar in principle to front filter caused flare.
I think we can all agree there is a mechanism for a front filter to cause unwanted images by reflection from the sensor. That is with glass, even anti-reflection coated glass. In the case of a semi-silvered mirror, one surface is much more reflective, and has potential to make things much worse.
For an angled mirror, as a rough 1st thought, I don't think sensor reflection to the mirror could cause additional images, as the light would be going in the wrong directions after refraction/reflection and wouldn't return to the sensor again. So for now, I think reflections within the mirror is the most likely cause.
I'd have to revise my optical physics equations to put numbers to that... and its a bit late in the night to start now.
Looking at it another way, any light ray hitting the mirror that is not perpendicular to the mirror will be refracted to some other non-perpendicular angle. It doesn't matter what that is exactly, but internal reflections will occur and could provide additional light paths offset from the main image. The level of that would be significantly reduced, but this is similar in principle to front filter caused flare.
I think we can all agree there is a mechanism for a front filter to cause unwanted images by reflection from the sensor. That is with glass, even anti-reflection coated glass. In the case of a semi-silvered mirror, one surface is much more reflective, and has potential to make things much worse.
For an angled mirror, as a rough 1st thought, I don't think sensor reflection to the mirror could cause additional images, as the light would be going in the wrong directions after refraction/reflection and wouldn't return to the sensor again. So for now, I think reflections within the mirror is the most likely cause.
I'd have to revise my optical physics equations to put numbers to that... and its a bit late in the night to start now.
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