F Craig Callahan writes, > But is there really a focal length multiplier in effect? Isn't it just that > the > digital sensor uses a smaller portion of the image circle presented by a lens, > so > that when the image is enlarged to any given size, the magnification of the > image > is greater with the digital image than with 35mm film enlarged to the same > size > (*not* by the same factor), thus producing a "multiplier" effect? Consider > that > putting a 2x converter on a lens and enlarging an image made with that same > lens > without converter by 2x will produce the exact same result in terms of > magnification and depth compression--isn't that essentially what's happening > with > the D30?. > > The corollary question is, does the angle of view of a lens change just > because > the receptor is smaller, or is angle of view strictly a function of the > physical > and optical design of the lens? I don't know, which is why I'm asking, but it > seems to me you would want the camera/flash combo to recognize the actual lens > you've mounted, and not some imaginary "multiplied" lens.
Yes, I agree, but only with the first part of your argument. All lenses, even 35mm ones, produce a circular image field. The image captured on film is merely a "bite" out of it. In the case of 35mm the circle of capture is barely larger than the film frame, but it exists nonetheless. A CCD/CMOS is smaller than a 35mm frame, so the photo made is a smaller section of the image coming through the lens; however, the lens is producing exactly the same size image circle regardless of the format behind it. The angle of view of the lens does not change (how can it?), but the smaller sectional area of the image circle used to form the picture changes the effective AoV as WE perceive it. It requires some lateral thinking to get ones head round this concept! So, when using a flash we need only to cover that part of the subject area that will be captured on our digital chip. Any extra is waste. This I'll cheerfully admit is theory only, the proof of the pudding is in the eating! I shall await Lars' test results eagerly :o) * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
