Re: How could the camera on missiles and smart bombs keep its focus?

"Sea Squid"

> But the camera has to stay in focus before it can shoot. In the movie, all > the pictures in the few frames before blackout are all in focus. >
** The depth of field ( aka depth of focus) of a lens with a small aperture is very wide - even a moderate telephoto lens can, when set to F16 or higher, be in good focus from a couple of metres to infinity.

Interestingly - the depth of field of a lens depends only on the size of the field of view and the F number. When the subject is very small ( ie like a postage stamp) then the depth diminishes to a millimetre or so.

........... Phil

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Phil Allison
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