SPOT METERING

Spot metering is a very accurate method of determining exposure.
It is also only for the experienced.

Most metering systems, and hand meters, determine an average
exposure by reading the general light level reflected by a
subject - or that falling on the subject, which is known as
incident light.

Spot meters can be bought as a separate unit, but many high spec.
cameras have spot metering built in. Some allow several readings
to be taken, and the camera then averages these. Spot metering
reads off an area of subject which will only be 1 or 2% of the
viewfinder area. This is usually defined by a circle in the
centre of the finder.

The skill is picking an area which will reflect light in exactly
the way you require. For example, a white area would tend to
indicate readings leading to general under exposure. A dark area
the opposite. A colour must be recognised that gives the
'correct' reflection. That is a colour which approximates to an
18% grey - grass can be quite good.



It is possible to buy a card known as an '18% Grey Card'. Kodak,
for one, manufacture these. If such a card is placed in a
position on which EXACTLY the same light is falling as on the
subject, and a spot reading taken of the card, then that reading
is almost certain to be correct.