Quote:
Originally Posted by Markulous
At least focal length is something that can't be messed with
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Actually...
Apparently the focal length is a bit flexible. I was trying to find out what it was acutally a measurement of.
Measuring Focal Length
Anyway, at the start of the article, you can find: -
Quote:
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In fact most lens makers will tell you that the focal length marked on a lens is +/- 5%. That means your 400mm could be as short as 380mm and still be "within spec". Normally telephoto lenses err on the short side. It's MUCH more likely that a lens will be shorter than marked than longer.
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It's a bit like a car manufacturer selling a Fandango 1.6L which is only 1580cc
Wonder if I can buy a lens costing £400 but only pay £380 on the basis that it's "nearly £400"