Take a Light Readingby Laurie McArthur

Reflected Light Readings for Film and Digital Images

n order to correctly expose your film or CCD there are two variables that must be identified: average reflectance and average light. Unless you have some good reason to meter for other than these two averages, stick meticulously to the method outlined below when you take a light reading.

This tutorial deals with reflected light readings. This is the type of light reading taken with an in-camera light meter or a hand held meter which is pointed toward the subject. This tutorial does not deal with incident light readings which are a measure of the light falling on the subject.

Average Reflectance

A white painted wall, snow or the ocean reflect most of the light falling on them. A burnt tree, a black fireplace or a coal mine reflect little of the light falling on them. A mid tone falls halfway between these extremes and reflects 18% of the light falling on it. The ISO rating of film or a digital CCD is set so this mid tone is exposed as a mid tone.

Identify a Mid Tone

Identify a mid tone for average reflectance and meter off that. Look for some green grass or foliage, mid tone rocks or bare dirt, weathered timber or whatever you can find that is somewhere in the middle between dull black and shiny white. If you are unable to escape a predominance of one extreme or the other in your framed image, then find an area to meter else where.

If need be, point the meter toward yourself and meter your clothes or else take your coat off, throw it on the ground and take a light reading off that.

Sand at the beach or the palm of your hand are about one stop too bright. These can be used to meter off but you must compensate and the likelihood of a mistake is introduced.