essential skills: digital photography in available light
Intensity
Light intensity is a description of the level of a light’s brightness. The intensity of light falling on a
subject can be measured using a light meter. This is called an ‘incident reading’. A light meter built
into a camera does not directly measure the intensity of light falling on the subject but the level of
light refl ected from it. This is called a ‘refl ected reading’.
Refl ectance
Regardless of the intensity of the light falling on the subject, different levels of light will be refl ected
from the subject. The amount of light refl ecting from a surface is called ‘subject refl ectance’. The
levels of refl ectance vary according to the color, texture and angle of the light to the subject. A
white shirt will refl ect more light than a black dress. A sheet of rusty metal will refl ect less light than
a mirror. In all cases the level of refl ectance is directly proportional to the viewpoint of the camera.
If the viewpoint of the camera is equal to the angle of the light to the subject the refl ectance level
will be greater. The level of refl ected light is therefore determined by:
~ Refl ectance of the subject.
~ Intensity of the light source.
~ Angle of viewpoint and light to subject.
~ Distance of the light source from the subject.
Although the intensity of the light source may remain constant (such as on a sunny
day) the level of refl ected light may vary.Itti Karuson