I m with Dick on this one I think the reverted change was far less readable and somewhat off the wall as well as technically incorrect in a few places I think we should stick with N as the symbol for the same reasons as Dick I don t understand what Glockenlang1 means by overloaded I also think we should stick with vast preponderance of reliable published sources rather than a self published web page I don t suggest that the article could not be improved For example I m uncomfortable with the concept of effective aperture diameter because the effective f number derives from an image distance greater than the focal length rather than a change in entrance pupil diameter