Letâ€™s go back to the zone system we were discussing earlier. Remember that each step on the chart represents one stop or EV. Altering the cameraâ€™s exposure by one stop moves the overall brightness of the scene by one zone. This allows us to set the exposure precisely to produce the correct tones in an image.
On this chart, which was originally developed for black and white photography and printing, the zones are roughly equivalent to the following scene elements (adapted from Adamsâ€™ descriptions):
Zone 0 - Pure black, no details or texture visible.
Zone 1 - Black tone but no texture. This is normally as black as you want to get in a picture.
Zone 2 - First hint of texture and detail, very deep shadow.
Zone 3 - Dark materials, details visible.
Zone 4 - Dark foliage. Dark stone. Landscape shadow. Shadow on portraits in sunlight.
Zone 5 - Clear north sky. Dark skin. Grey stone. Weathered wood. 18 per cent mid grey.
Zone 6 - Average Caucasian skin value. Light stone. Shadows in sunlit snow.
Zone 7 - Very light skin. Light grey objects. Snow with side lighting.
Zone 8 - White with texture. Snow in shade. Highlights on Caucasian skin.
Zone 9 - Glaring white surfaces. Snow in flat sunlight. White without texture.
Zone 10 - Light sources, reflections of sunlight on metal. Pure white.
To use this system effectively, it really helps to have a spot meter. This is a lightmeter that measures light from a very narrow angle, typically just two or three degrees in the centre of the frame. Hand-held spot meters are best, but they are very expensive. However many digital cameras these days have spot metering as a built-in option. If your camera has a setting that looks like either of these, youâ€™re in luck.
If you donâ€™t have a spot meter you can get around this to a certain extent by zooming in on the area to be metered, or holding your camera closer to it, and noting down the exposure reading. Itâ€™s not ideal, but it can work.