What
is a light meter?
CDs Light
Meter
This type of meter is externally similar to the selenium cell
meter, but it has a smaller cell. It is driven by a battery
instead of a solar cell. Cds or Cadmium sulphide cells are photo-resistance;
meaning that its electrical resistance changes in proportion
to the light it receives. This type of meter is much more sensitive
and can even give readings in moonlight but only work when the
battery is circuit.
|
Move over image
to view roll over image
|
A supplementary
light diffusing dome fits over the cell or slides along to cover
it is often included for incident light
readings which are readings from the light rather than the
subject |
Move over image to
view roll over image |
However
they are rather slow to register their readings and bright light conditions
tend to be remembered by the cell for some time, so you may have to wait
a few minutes after measuring in bright sunshine before using the meter
indoors. They may slightly over respond to red. Note a red needle
indicates a number on the scale which is then transferred by turning the
dial to match the number. The scale can be changed from high to low by
moving the slide at the top of the meter. Once the dial is rotated to
match this number the aperture setting (lower figure) and a the shutter
speed (upper figure) can be selected from the dial.
Like all
light meters, remember to set the film speed.