Photo Practice - Nikon D90 User Manual

10. Photo practice

With a Nikon D90 camera in a HUGYFOT housing one can take pictures almost
completely automated. To use the camera with all its possibilities one has to
beware of some basic principles. These basic principles are explained in the
following chapter.
The "Auto Focus system" (AF) lets the camera focus in most cases, sup-
posing that the subject is positioned in the centre of the viewer. If not one
has to focus on the subject and keep the shutter release button squeezed.
This way the focus is locked. One can now adjust the composition and
shoot. When taking macro images the depth of field is more narrow and
therefore the AF-system can be defective by particles in suspension. In that
case, focus on the subject and lock this position according to the technique
mentioned above. Next, approach or move away from the subject until it is
focussed and press the exposure lever. Due to diffusion and absorption of
light under water, photography under water is limited to a distance of about
1,5 meters. Nevertheless, shots from a distance of over 1,5 meters are pos-
sible but the quality of color, sharpness and glow will be considerably less.
Therefore the golden rule in underwater photography states: "The closer
the subject is photographed, the more attractive the colours and the more
sharpen the shots willl be."
When adjusting the "diaphragm", one has to consider a decreasing depth
of field when increasing values of the diaphragm are selected. This depth of
field decreases when close up shots are made.
With a longer "shutter speed", more light can be catched and the bright-
ness of the shots can be increased. The shutter speed is always to be con-
sidered in combination with the diaphragm. The built-in light sensor informs
the photographer about the effects of the combination he wishes to apply.
Always consider that shutter speeds slower than 1/60 second could result
in motion blur.
Hugyfot Housing for Nikon D90 23 User manual