A Flash in the dark

Barrie Smith
15 April, 2008
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Flash is possibly the most used, and then again the most misused function on a digital camera. How many times have you seen TV broadcasts at night from a huge sports arena and, just as the player/athlete does his or her magic trick, all the cameras in the audience section fire up and betray their presence with their telltale flash? It’s as sure as the sun rises you can guarantee those poor snappy souls will get nix, nowt, da nada in the way of a useful picture. Most likely, they will get a black, underexposed frame, if anything at all.

Why? For one thing, the flash is insufficiently powerful to light up a person on the field who is probably 20 or more metres away. The other factor is that, in flash-taking mode, most cameras will stop down to a smaller lens aperture, so ensuring that not only will the flash will not light up the action but the camera will underexpose it as well.

What to do? Turn off the flash (it’s called "forced off") and wind up your ISO setting to 400, 800 or more. Sure, you’ll probably get noise in the image — but at least you get an image and probably an unrepeatable one of the action as well. Oh and you will need to hold the camera steady if the shutter speed is slowed down in the dark environment.

The use of flash in the outdoors when taking people shots can also be an enormous boost to your photo taking efforts: set your camera’s flash mode to "forced on" or similar. That way you’ll get a normally-exposed shot plus the flash — as an auxiliary light source — will lighten up the eyes and other facial features of the person in front of your camera.

However, the big message is: look up the flash specs for your camera. Here you’ll find some data about the flash coverage, usually expressed as "W/T 50/60 cm to 3.0/2.0 m" — or something similar. This means that the camera’s flash cell will correctly expose the shot at any distance between 50cm and 3.0 metres — if the lens is set to wide angle. With the lens set to the tele end of the zoom, the flash output will bring home the shot if the subject is between 60cm and 2.0 metres.

Some camera manuals will specify that these figures apply with the ISO sensitivity to 100. Increase the sensitivity and you get more flash coverage — but at the risk of overexposing the picture at close range. The odd thing is that, if you use the lens at the tele setting, you lose light coverage. Why? Because the lenses of all compact cameras lose an f stop or more when moved from wide angle to tele.

Another factor that intervenes in the flash business is when you shoot outdoors at night: you will get less power from the flash. Shoot indoors and you get more. Why? Indoors the ceiling and walls help bounced the light back on to your subject, acting like a fill light.

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