Contrast Ratio

The Contrast Ratio is the amount of light in the darkest part of a scene compared to the light from the whitest part. Your eye can see detail in very dark and very light areas – even if the light bit is a thousand times as bright as the dark bit. Cameras aren’t nearly as good: photographic film can show detail in a picture with about eighty to one brightness ratio; video isn’t yet quite that good. Adjusting light to get a decent shot can mean problems. Here’s a visitor being admitted to a house, with bright daylight in the back of shot. On the left is what your eye would see; right is how a camera would show things.

In this particular location, there’s not a lot you can do about things, apart from throwing light on his face – and you need a lot of light to compete with the sun. Or you could shoot the scene at dusk, when you wouldn’t need quite as much light to make the face visitble. You might be able to find a front door – maybe in a block of flats – where there’s a wall opposite, not in full sunlight. It doesn’t have to be the front door of the place where the rest of the scene will be shot – as long as we don’t see the door later. Or you might be able to move the camera slightly to one side, maybe track back and zoom at the same time, so that the background is shady trees. Like this pair of shots:

Of course, in many situations you can’t get by without adding light. You can use ordinary standard lamps, perhaps with some aluminium foil wrapped around the shade to direct the light. If you want more control, though, you need to borrow, beg, buy or hire some professional lamps.

Redheads, Blondes, Broads and so on

Lights come in all shapes and sizes. The one above is the film-maker’s workhorse, the Redhead. I know it’s blue – the originals were bright red.

Anyway you’re really only concerned with two things; the power of the light and whether it’s a hard or soft source. The power can vary from little ten or twenty watt things up to several kilowatts, but most small crews use lights that use three hundred to six hundred watt tungsten bulbs for hard light sources and fifty watt LED slabs for sof light.

Don’t worry for the moment why you might need a hard or a soft source – I’ll cover that later.

A hard light in its simplest form is a bare bulb. If you just stick a bulb near a face, though, you’re wasting most of the light. So most hard source lamps use a reflector (like a torch) and/or a lens on the front to direct the light much more efficiently. In addition the light will probably be fitted with shutters or barn doors to give even more control. (You may want to light up a person, but not the hard white wall to the side, for instance).

You can make a hard light into a soft light by clipping translucent gel or tracing paper to the barndoors, or by bouncing the light off a reflecting surface of some kind. Expanded polystyrene is everywhere, light enough to tape to any surface and very cheap.

You can buy purpose made soft lamps; you’ve probably seen a photographer’s umbrella lamp. It’s a fancy variation on the expanded polystyrene theme. There are various lamps with a built-in translucent screen (or an add-on frame). They work on the same principle as sticking the white gel in front of the light, but they generally give a larger, therefore softer, light. In addition, there are flat lamps with banks of special fluorescent tubes. They give a cool, soft light, but they’re a bit unusual outside the studio. For most purposes you can light almost anything with three or four simple reflector lamps.

Well, as I hinted in the bit about contrast ratio, using natural light often doesn’t look very natural! You need to give nature a helping hand. Lighting setups vary enormously, but they all rely on the same basic principle – three point lighting.