Greetings ladies and gentlemen:
I'd like to raise a few points regarding focal length and angle of coverage.
It is usually suggested that those of us switching from 35 mm to 4x5 multiply their favorite focal length in that format by 3, and that this will yield the 4x5 equivalents. However, that doesn't seem to be an accurate translation of focal lengths or angles of coverage. For example, a 50mm lens on a 35mm camera has an angle of coverage of 46.8 degrees as the angle of view is determined by focal length and film size. A 150mm lens on a 4x5 camera, on the other hand, gives us 56.145 degrees. A 35mm lens on a 35mm camera has an angle of view of 63 degrees but its triple focal length on a 4x5 camera has almost 75 degrees.
My point is that it is the angle of view that makes us choose a particular lens, although we may express our choice in terms of focal length. Therefore, multiplying a small format camera's focal length by 3 doesn't seem to be satisfactory.
Am I missing something?
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