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Subject: Re: You use different lenses underwater because the speed of light is different




Dave Hillstrom wrote:
> You can't use regular lenses underwater, that's why you always see
> special cameras on ocean documentaries and such. People think it's
> because they need to be waterproof but the real reason is the speed of
> light underwater is different than in air and it makes the light bend
> at different angles through the lenses.
> Einstein proved it.

So, I suppose that is also the reason you need different lenses to take
telephoto pictures than the lenses you would use for wide angle. Light
from different distances travels at different speeds? No doubt this is
due to the fact that light traveling from farther away has to go
through more haze, so it passes through more water on the way to the
camera. It would explain depth of field, too. A lens set at a
particular focal length can only bend light traveling at a particular
speed at the correct angle. Light that is going too fast or too slow
would, of course, bend at the wrong angle and thus the foreground and
background are out of focus. That being the case, you would also need
special lenses in space, where light does not travel through any water
at all.

Or maybe it is just wrong to encourage this nut.


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