T3D Re: Underwater stereo photography

[michaelk@xxxxxxxxxxx (Michael Kersenbrock)]

> > How about focal lengths?  Is 35 mm short enough for UW photography?
> 
>     With underwater photography, the shorter the focal length, the
>     better!  But perhaps not for the reasons you would first think.  A
>     35mm is OK, but a 28mm is preferred.  And the lens that most
>     Nikonos owners lust after?  The 15mm!  (A very expensive piece of
>     glass -- and this for a lens that only works underwater!)  Why so
>     short?  Visibility is always a problem in the water.  Even in the
>     gin-clear waters of the Caribbean, you want to have as little
>     water between your lens and your subject as possible.  More water
>     means more particles which means more backscatter from the flash,
>     etc.

In my book "Camera Below, the complete guide to the art and science 
of underwater photography" by Hank Frey and Paul Tzimoulis (an oldie, 
1968) it has a full page chart which includes the following:

For full-frame 35mm Cameras:

F.L. in Air   F.L. in Water/Air
-----------    ----------------
    21               28
    28               37.3
    35               46.7
    50               66.7


It also says that wide angle lenses are the most appropriate and that
the reason to want it that way is that "it allows you to shorten
the distance between yourself and your subject. A shorter camera-to-subject
distance means fewer turbidity particles in the path and better contrast
and brilliance of colors."

Which is pretty much what Bill said, but thought I'd include the
chart (it actually has more entries for 35mm and other sets of f.l.'s
for other camera formats).  It also gives the angles the f.l.'s represent.

Mike K.


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