underwater Photo Course :: (2) Equipment Guide :: Underwater Camera Housings :: Lenses and optics
Lenses and optics underwater
U/W Photo Course
Learn u/w photography the easy way!
Whether you opt for an underwater camera or
housed camera you will also need the right lenses to make it work to full potential. In this area
a great deal of confusion exists.
We still relate to the
Focal LengthThe focal length of a simple symmetrical lens is the distance between the image plane (e.g. the film) and the middle of the lens when light from infinity is brought to a focus.
of film cameras when describing the
Angle Of CoverageThe angle between rays of light entering a lens from the extreme corners of a scene. AKA angle of view (AOV)
of detachable lenses, even if used on digital SLR's. It is convenient to have one reference point but it is
another source of confusion! Point and shoot camera lenses are often quoted as having an 'equivalent lens to...' .You must apply a
Focal Length MultiplierThe Focal Length Multiplier is a figure to apply to 35mm lenses to calculate their true focal length on digital cameras that do not have full frame sensors.
to lenses on digital cameras.
Lenses are identified by their focal length in millimeters (mm). The 'standard' lens for underwater photography is the 35mm - insofar as it
approximates what you see. Your photographic opportunities would, however, be somewhat
limited if the standard lens were the only focal length of lens available. The
U/W standard lens is more like the 20mm, which has approximately 90 degrees
angle of view.
Indeed, there are lenses where the focal length is less than the diagonal i.e. wide
angle, and lenses with a focal length greater i.e. telephoto. Underwater photography suits
the extremes of subject sizes. Subjects are either close and small (macroPhotography of smaller subjects shot (between 1:1 and 1:3) on macro settings or with macro equipment) or close and
large (wide angle). The most useful lenses are therefore wide angle or those
having close focus (macro) facility.
Next >> Lens Types