Outdoor Focus Spring 2019 - Page 9

www.ronaldturnbull.co.uk What is White? We know what yellow is. Yellow light is given off by car indicators and sodium streetlights. It’s clustered around the part of the spectrum that stimulates the R(ed) and G(reen) sensors in the backs of our eyes, while leaving our B(lue) sensors unbothered. And a yellow object, like a banana, refl ects back any yellow light falling on it, while absorbing the red, blue and purple. Some say there’s no such colour as ‘white’. Which is silly, as you can also off ers the old-fashioned light bulb (Incandescent, or sometimes Tungsten), and one for Flash. And for those of us who really can’t be bothered, there’s the Auto White Balance (AWB) setting. Sunset The sun’s going down, and there’s a pinky glow across the snowfi elds. ‘What’s that nasty pinky glow?’ says Camera, and cunningly go into Homebase and buy white paint just like yellow or magnolia. A white object, such as a snowfi eld, is simply one which refl ects back all of the light falling on it and doesn’t absorb any. But then, what is ‘white’ light? Using the same defi nition as for yellow, we’d say that white light is ‘all of the light that may be falling on an object’. Which just says that white light is light – not too helpful. We could defi ne ‘white’ light as: an equal amount of all the diff erent coloured wavelengths. Trouble adjusts AWB to get rid of it. But that pinky glow was what we were taking the pictures of! You can use AWB in the evening – or you can save the bother of deleting the disappointing photos afterwards, and just clear off down to the nearest pub. Using AWB does the job of recording colours worse than our old, ignorant fi lm camera would have done. During the golden hour leading is, there’s an infi nite number of wavelengths, and no way to say what makes up an ‘equal’ amount of each of them. Weirdly, this meant that there’s no such thing as white light. What the human eyeball does is pick out some objects it knows are white ones: snowfi elds, clouds, other people’s eyeballs. Then it takes whatever light is falling on them as being, for the time being, ‘white light’. Unless it happens to be sunset or something. up to sunset, I fi nd Daylight gives a fair rendering what I actually saw. As the sky reddens, I switch to Cloudy. For purplish post-sunset dusk, even the Shade setting can work. You could try switching around among them. And while you’re switching, give old AWB a go. Just to confi rm that all that work you put in fi nding the WB button really was worth it... Daylight The colour of sun light changes over the course of a day, from red-orange when the sun is close to the horizon to a spectrum with more blue in it when the sun’s high in the sky. (In winter, perversely, the sunlight stays near-horizon ‘warm’ all day.) Daylight assumes that the sun is directly overhead, when sunlight is closest to what it started off as: the natural radiation of a white-hot object at 5500° Kelvin. (Ah, so that’s why my colour-balance slider is measured in degrees K!) AWB Here a camera tries to do what our eyes and brains do so cleverly: assess a scene, work out what the incoming lighting actually is, and adjust accordingly. It works most the time. In particular, iPhones and the like have artifi cial intelligence that’s tremendously clever at working out what the colours really would have been. iPhones sometimes go even further, adding pizazz and luridness to suit Instagram tastes. So no more sitting about in a cave waiting for the magic pre-sunset light. iOS applies that magic lighting anyway, saving you time, a damp bum and a nasty cold in the head. Cloudy On a grey dreary overcast day, really interesting rock architecture can make a decent picture anyway. Except, when you get the picture back home on the screen, it didn’t. There’s a kind of dreariness fi lter spoiling your careful composition. This is actually a blue cast in the light, neutralised out by your brain at the time and, to some extent, by the AWB in the camera. But Cloudy does a better job. So, no more relaxing on the grey days and stuffi ng the camera in the sack. Switch WB to Cloudy and get back to work! Shade Inside Lord’s Rake gully, on a sunny day – this is lit not by sun but by the blue sky, and is even more blue-spectrum than overcast light. To add some colour to the gloomy blueness, you either need to dress your companions in orange or, use Shade, which will return much-needed warmth to the shot. Incandescent Old fashioned light bulbs and candles give a yellow light. (Yes, it’s the natural radiation of an incandescent object at 3500°K - viz, the little bit of wire in the light bulb.) Before White Balance, indoor photos without fl ash had a homely golden glow. To retain that warm glow, keep the camera on Daylight. To get rid of it, and capture what the adapted eye would actually have perceived, switch to Incandescent. Shoot outdoors with Incandescent and you get revolting bluey pictures that make you wish you’d never found out about white balance in the fi rst place. Flash Light from fl ash is slightly bluer (‘cooler’) than natural, but with a somewhat diff erent mix of wavelengths. (The colour can vary depending on the power setting selected, and also the age of the fl ash.) OF’s editor sometimes uses Flash in the daytime, for a subtly ‘lukewarm’ colour palette. spring 2019 | Outdoor focus 9