Painting with Light
If you’ll be shooting with something like a basic smartphone, please feel free to ignore most of this; the controls on most telephones don’t allow you much freedom.
Though you might consider an application like DSLR Pro if you’ve got an Android machine. There’s probably a similar thing for an iPhone.
A modern compact or telephone camera will give good results about ninety percent of the time, but if you can control things, you should get good pictures one hundred percent of the time.
The main things you have to worry about with light are:
- Exposure – getting enough light on the scene
- The colour of the light – the yellowness or blueness of a shot
- Contrast ratio – cameras don’t like deep black or shiny white
- Light source – what light(s) to use
- Naturalness – does it seem ‘right’ or artificial?
Well without any light at all you wouldn’t be able to shoot. At its simplest, you need to put enough light on the subject to enable the camera to expose the film, chip or whatever.
And don’t be fooled by manufacturers’ specifications that include things like, “Shoot in only 1.5 lux – imagine shooting your daughter blowing out the candles on her birthday cake with no extra lighting”. Well the shot will be crap for quite a few reasons; it will be grainy and noisy (I’m sure you’ve seen a shot where the gain has been turned right up and there are little white and/or coloured dots cluttering up the scene). And almost certainly, there will be a vertical white bar top to bottom of the frame on each candle. Worse – when she blows out the candles she’ll vanish!
White is white is white. Or is it? Well, not quite. The sun is white – but when it’s on the horizon it looks red. And anyone standing facing it will look a bit reddish-orange If you walk from a room lit by ordinary domestic sixty watt bulbs to one flooded by fluorescent light, the ‘feel’ of the light is cold, hard, blue-green (and maybe a bit flickery).
In general you’re not too aware of the colour temperature of the light, because your eye compensates for it in the same way as your iris opens and closes to suit the amount of light incoming. If you’re talking to a friend in a white shirt outdoors and you move indoors your brain knows that it’s the same shirt and compensates for the colour of the indoor lighting without you having to do anything.
Scientists measure the redness or blueness of light by temperature. Heat a bit of steel up to 5,600 degrees Kelvin (whoever he is) and it will glow a very blueish white – approximately the same colour as average sunlight. Let it cool a bit to about 3,200 degrees and you’ve got the same colour as ordinary household lighting. Just in case you’re wondering, Kelvin equals Centigrade plus 273 degrees.
There are many variations: sunlight at noon in some countries can reach twenty thousand degrees; photofloods are slightly hotter (more blue) than ordinary household tungsten lights; a light on a very long extension cord would give a more orange light, etc., etc.
Of course, the light from the metal bar or the sun isn’t of one particular wavelength; sunlight has rays of every shade from infra-red to ultra-violet. It’s just that the sun has more of the blue end – a domestic bulb gives more red.
Flourescents and LEDs
LEDs in particular are replacing tungsten lights very rapidly. But be careful; not all LEDs are equal. Those sold for photographic use should be fine, but some cheaper ones aren’t necessarily suitable. Better bulbs should be marked with a colour rendering index (CRI), and anything over about ninety is good.
Even the best LEDs have a fairly lumpy response curve. Google CRI to see some examples. Here’s a photograph shot by tungsten and then the same subject with a good LED soft light:
Hardly any difference to be seen in the bear’s coat, but his jacket shows that there’s a dip in the red part of the curve. Two reds that alre almost identical to the eye can be rendered quite differently on screen.