chandler wrote: > > The term "magnification" usually means the (physical) image size divided > by the object size. Well, actually a 2x magnified object appears 4 times larger :-) Magnification refers to linear dimensions. > 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, It's extraordinarily sensible. Macro starts when the image size equals the object size. How simple is that? The calculations can then ignore film size. Beautiful. Imagine if the calculations were based on a "typical" enlargement! You'd have a mess like DOF calculations. Now, in the case of DOF, it makes sense -- but not for magnification. > 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. Degree of closeness? Let me tell you that to get a butterfly filling the frame on 8x10 is a remarkably different kettle of fish than doing the same with 35mm. Magnification having the meaning it does (i.e. magnification at the film plane) is very important for calculating exposure. However, since we will probably have a whole generation of photographers who will never see a light meter -- apart from a thing in their viewfinder (if indeed it even makes a showing there) -- the definition of macro is really a dead issue. Lets hope they can hold the camera still for long enough :-) Steve
