Seeing the Light

[NarendZORCE]

taken from: http://www.istockphoto.com/article_view?ID=183

What is daylight? Glad you asked. Daylight is made up of two main light sources - sunlight, and skylight. Skylight is light that bounces off the inside of the curved atmosphere that surrounds the earth, often referred to as 'the sky'. The overhead angle of the sun, and other factors such as the amount of cloud cover, determine the mix of skylight and sunlight in any given outdoor scene.

So, just skylight and sunlight then? There's a third light source that needs to be taken into account if we're going to be able to calculate our exposures and white balance correctly. We also need to consider the colour and intensity of light bouncing from the ground, and other reflective objects in our immediate location.

I keep hearing about the colour of light around here. What does that mean? What colour is daylight? It depends on the light mix. Skylight is blue in colour, so more skylight in a scene means a bluer image. Sunlight, on the other hand, is reddish/yellow in colour, just like the sun. Reflected light will have a hue similar to the colour of the object it bounces off. Skylight is the reason we can still see things in shadows, which are totally void of sunlight. When we're out of the shade, we usually stand in a mix of sunlight and skylight. Because skylight is already bounced, it is more diffuse than sunlight. Light that streams through a cloud will also be softened and spread about, which helps us make good photos.

How do we measure the colour of light? We measure the 'colour temperature' of light on a scale of degrees kelvin (k). Scientists use the kelvin scale to measure the amount of light a bar of metal emits when heated. A metal bar heated to 1,000k will emit the same amount of light as a burning candle. If the bar is heated to 3,000k it glows as bright as a household lightbulb. If we crank it up to 6,000k you're getting close to the amount of light produced by a hotshoe mounted flash. As photographers, we deal with colour temperatures that fall roughly between 2,000k (a sunset) and 11,000k (pure blue sky). The light at noon, when the sun is directly overhead, will have a temperature of about 5,500k and is considered to be 'colourless' (it is also widely considered to be harsh and useless because it's coming straight down through the atmosphere at right angles, with nothing to diffuse it). The light on a hazy day has

a temperature of about 8,000K. At sunset the numbers are generally between 2,000k and 3,000k, and the light from a flash is colour balanced to 6,000k. Cooler light (lower kelvin numbers) will result in a redder image, and hotter light (higher kelvin numbers) will give you an image with bluer tones overall. This might seem odd at first, as we often associate blue with cool, and red with hot. But, remember, a blue flame is actually hotter than a red flame, as anyone who has lit a cigar off a bunsen-burner will attest.

Who cares? We do! Photographers need to know the approximate colour temperature of the available light so that we can get the white balance right on our cameras. Your amazing eyes are constantly adjusting to the ambient light, so that white always looks white. Your camera, on the other hand, is bog stupid. It needs to be told, or allowed to guess, the temperature of the light when the shutter button is pushed. We're trying to get your camera to see what your eyeball is seeing.

Isn't there a machine that can do this for me? Yes, and you probably already own it. Your camera, while bog stupid, is, nonetheless, a sophisticated piece of circuitry that usually comes close to estimating the actual colour temperature of the scene. Leaving your white balance set to auto is a good option if everything I've said so far made you dizzy. A light meter could also save your brain. If you shoot RAW you can set and even change the colour temperature when you sit down at home to edit your images. It affords you the luxury of concentrating on other things, like where you put your lens cap.

So, everything you've said so far is academic? No. It's boring, but important. You need to be able to understand these concepts to assess the quality of, and ultimately, see the light. This is more than just a figure of speech - it's more like an epiphany. It's a vital skill for landscapes, macro shots and portraits alike, and if you grasp the fundamentals you can improve any type of photography you undertake.

Enough boring theory! Just tell me how to take the h*cking shot. Sheesh, you're keen. But this is supposed to be a dumbed-down Q&A and that, strictly speaking, isn't a question. Besides, there's more to it. Try to slow down a bit and we'll get to the stuff about the magic beans soon, I promise. Go on then...

What else do I need to know before getting the camera out of the crumpler? Let's abandon Kelvin for the moment and focus on what we can see. Hold your arm up in front of you with your thumb pointing towards your forehead and look at how the light falls on your forearm. In an ordinary lighting situation, one side of your arm will be darker than the other, depending on the angle of the lightsource. There you go, that's your first prac, wax-on/wax-off stylee.

Do I need to get up early? It would certainly help, but you can also shoot in the late afternoon if your body clock runs out of batteries in the morning. The quality of late afternoon light is often superior to early morning , but if you shoot at daybreak, there are vastly less people awake to ruin your shot. How early you need to get up depends on your latitude more than your attitude. The sun rises quickly in some places, and the gentle low angled light might be as brief as it is flattering in your part of the world. Morning sunlight give us warm images because the oblique angle of the sun means light needs to pass through more atmosphere to get to our lens. The dense atmosphere around the middle of the earth weakens the intensity of the light, but compensates by diffusing it nicely and scattering it around. Most of the light you see at this time of day is actually reflected skylight which, as we know, gives subjects a bluish tint. Morning light changes constantly as the sun climbs higher and warms the earth, which in turn gets the clouds moving. Don't be put off by cloudy skies, though, as early morning light and overcast weather can provide ideal even lighting conditions. Late afternoon light is also a bit special, but in a different way. We could be talking about a span of five minutes here, or a few hours. You've just got to be there, waiting. After a certain time of day the wind drops, the nasty contrasty light is gone, shadows get longer and softer. Reflections start to show up on still water that suddenly looks like stained glass. Our mate kelvin is really warming up the tones at this time of day, and the simplest scene can become spectacular in a heartbeat, and then ordinary again a second later.