Nikon lens not what it purports to be
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17-07-12, 06:10 PM
Join Date: Sep 2010
Location: Hove, actually
In theory, the marked focal length should be accurate to about 1%. Yours clearly isn't within this limit.
There are a number of factors that could cause a change in focal length when no change should occur, and as pointed out, focusing is one of them.
I haven't bothered to check, but from memory infinity for a camera lens is usually taken to mean about 1000 times the focal length; in the case of a 70mm lens if I've used the Windows calculator correctly that would be around 83 yards.
For what it's worth, I'm not a regular here and only just saw your post.
Last edited by StephenBatey; 17-07-12 at
. Reason: Typos
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