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Contrast Ratio for a DV Shoot

The best way to cope with contrast ratio when lighting for a DV shoot

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If you look at a person standing in front of a window during the day, you can see the detail in their face as well as the outside world.

But a TV system can only calculate the correct exposure for either the face ot the outside world. Get the face correct and the background is overexposed, expose for the background and the person becomes a silhouette.

Contrast Ratio

The difference between the brightest and darkest parts of a scene is called the contrast ratio. The human eye can cope with a contrast ratio in excess of 1000 to 1 where as the TV system (camera, tape, transmission and TV set), is limited to around 40 to 1.

To enable TV to cope with a person in front of a window we need to reduce the contrast ratio.

So what are the options?

The easiest option is to move the shoot, but then you lose the shot. You can reduce the amount of light coming in through the window by covering it with gels, but this is time consuming and expensive. Alternatively you can put more light on the face.

Not all contrast problems are so obvious. A person standing at right angles to a window will often have too large a contrast range across their face. You have to expose for the brightest side leaving the shadowed side too dark.

A subtle fill light is needed to balance this side of the face so that the TV can reproduce the scene our eyes see. This can often be done simply by placing a reflector in the right place.

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For more information on lighting for DV check out these courses:

DV lighting and Safety Workshop (face to face)
DV Lighting Safety (online)

This article was written by Ian Hider - TV Operations Specialist at BBC Training & Development.