
Originally Posted by
Chris Korman
Can't one say that a compound lens can be reduced to single element? For if you do ray tracing, you are only interested in how the incident light ray is deviated from front element to that of the rear element. (aka a transfer function). I think would make sense from even the transformation matrices standpoint in that you are in effect multiplying them together to get the equivalent single matrix. Or from a more practical point of view this is useful for establishing the real "focal length" of say a reflex/mirror lens.