All air/glass interfaces are an abrupt change in impedance for the electromagnetic energy impinging on/passing through the interface. A portion of the light must be reflected at each interface. In fact, the same amount of light will be reflected at the inner interface as from the outer interface. Lost light is not really the problem for a single glass. What would you loose, a third of a stop at most? Light reflected from the inner interface, reaches the outer interface and a portion of that is reflected back toward the film. Some is transmitted. If the light is bright, such as a sun reflection off chrome, the reflection will be seen because it's now bright compared to the image. This is flair. You may try single coated optics, but by their very nature, they can perform a perfect impedance transformation at only one wavelength. For this reason, single coated optics must have some affect on color, that is, demonstrate some color cast, however mild.
The reason for multi-coated optics is broad band impedance transformation. Most of us don't think this way, but it is what's happening. Regards, Bob... --------------------------------------------------- "Beer is proof that God loves us and wants us to be happy" - Benjamin Franklin From: "Gregory L. Hansen" <[EMAIL PROTECTED]> > How important is it to have a coatings on all your filters? A plain UV > filter might cost $10 while an SMC filter would cost $35. I can't see how > it would matter much on the outer surface, a little bit of light would > just be lost. But on the inner surface?
