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Matt, Question on the focal length of a lens.
How do manufactures measure the focal length of a lens.
my uneducated thought would be the following.
50mm lens
Using a full frame sensor size cutout i.e. an old picture slide, holding the slide up 50mm away from your eye is this what a 50mm lens would be measured to replicate ???
If not how is the measurement of a 50mm lens done.