[?]zzet <izzet@vizo.com> writes: (The first character of your name appears on my monitor as Japanese phonetic 'so'. I'm sure that isn't right, but I don't know what it's meant to be.) > Hi all, > > We all know that focal lengths of digital cameras are given as 35 mm. > equivalent focal length due to small size of the ccds. I have seen in > lots of places, that this is explained as "this is the focal length that > gives the same magnification as a 35 mm. camera". > > I may be missing something but I think that the only equivalency is in > relation to the field of view, not magnification. I think you understand it right, basically, despite the efforts of the dumbing-down crowd to confuse you. The focal length of a lens is the distance from optical centre (rear node, I think) to an image formed of an object (subject) at infinity. End of definition. The problem is that people use the focal length of a lens for 35mm format to specify the angle of view, and perhaps the original writer thought that "magnification" was another way of saying "angle of view". The term "magnification" usually means the (physical) image size divided by the object size. Unfortunately, they then for example use "macro" to mean 1:1 or bigger in a particular format, typically 35mm; this isn't really very sensible, because the effective 'degree of closeupness' of an image is really the size of the subject. So if you have a butterfly with a 2cm wingspan, and photograph it frame-filling with large format, 35mm, and a typical CCD camera, the optical magnification is wildly different, but the 'degree of closeupness' is the same. HTH This message brought to you at 8 bits per character, spaced 4 light years, 3 ells, and a carrot apart. Brian Chandler ---------------- geo://Sano.Japan.Planet_3 http://imaginatorium.org/
