Do you know what the difference is between a good photographer and a great one?
It's light. Or rather, the way the photographer uses light. A good photographer knows how to compose an image, how to angle her camera so the viewer gets a completely unique perspective of an object, how to capture an event in an interesting and unusual way - even how to capture an emotion. A great photographer does all of this in the right light.
Light is pervasive, and because of this you may not always be consciously aware of it - unless it's either blinding you or fading from view. Most of the rest of the time, light just is, so we don't pay much attention to it. For this reason you may spend a lot of time just snapping photos without really thinking about the quality of the light.
But it's worthwhile paying attention because you'll get some stunning results...
[ Top image blue hour by Flickr user Will Montague]
Gecenin Koynunda / In the Night's Soul by Flickr user Kuzeytac
Natural vs. artificial light
As far as photographers are concerned, light falls into two broad categories: natural and artificial. Both categories include subsets of light that have different properties from one another. For example, natural light is usually produced by the sun, but natural light can also come from flames such as a candle or even a forest fire. Moonlight is also a form of natural light. But even though all these types of light come from natural sources, they have vastly different characteristics. Candle light, for example, will produce light with an orange cast while the mid-day sun produces light that is much bluer. Even the properties of sunlight can be vastly different during one time of the day than during another: morning sunlight, for example, is diffuse and produces softer shadows, while the sun at noon is direct and produces darker shadows.
A Chilly Night in Boston by Flickr user Stuck in Customs
Artificial light, of course, is any kind of light made by human beings. This can range from those noisy fluorescents in an old office building to your state-of-the-art set of studio equipment. Various types of artificial light will also have different characteristics. A bare bulb gives off a vastly different kind of light than a soft-box does. It is also colored differently: most standard lighting is yellowish in color, while photographic lighting is usually balanced to simulate sunlight.
There is a science behind all these differences in light, and understanding the basics of light characteristics and properties will help you produce better photographs.
The characteristics of light
Almost everyone who owns a camera has heard the terms "hard light" and "soft light." The meanings of these terms are fairly self-explanatory, but in a nutshell: hard light creates hard shadows, and soft light creates soft shadows. Hard light is caused by a small, directional light source such as the sun. Soft light, on the other hand, comes from a large or filtered light source. On a cloudy day, that hard light source known as the sun is filtered by the clouds, which produces soft light. Reflected light is also soft, as long as it is reflected from a large surface such as a wall or one of your portable reflectors.
MANN by Flickr user flickrolf
You've probably been told to avoid hard light and use soft light where ever possible. And for the most part, this is true. Soft light gives you a better range of tones, and it brings out more detail in the shadows. Hard light gives you more contrast, and can result in photos with "blown out" highlights and black shadows.
There is a place for hard light in photography, despite what you may have been told. If you want to emphasize harshness or bleakness in a particular scene, for example, noon on a cloudless day might be exactly the right time to shoot that scene. If you're shooting a model and you want that golden-era of Hollywood look, you would also choose hard light. If you are shooting a textured surface and you want to emphasize the texture, hard light is a good choice for this, too.
Folds by Flickr user Shootingsnow
Most of the rest of the time, you will want to stick with soft light, such as the light you find during those magic hours just after sunrise and just before sunset. Soft light brings out the detail in whatever you are shooting, and it tends to be much more flattering to people. And, as I've said, it gives you a better range of tones and more detail in highlights and shadows.
You've probably heard this term, too, which is one of those "huh?" terms. How can a color have a temperature? Well, simply put, color temperature is the temperature of an ideal black body radiator as it is radiating light of a hue comparable to that of the light source in question. Now that that's as clear as the summer sun, we can move on.
Oh wait, that wasn't clear? That's because as a technical concept, color temperature really isn't that easy to explain. So forget all that "black body radiator" stuff (unless you want to impress people), because all you really need to know is that different types of light have different color casts. Ah, now it's starting to sound familiar: lightbulbs give off a warm yellowish or orangish cast, and the sun gives off a cool bluish cast. Color temperature is measured on the Kelvin scale; for example, a candle's flame is 1,200K, which is towards the orangish end of the scale, and a cloudless day is 10,000K, which is at the blue end.
1/52 ~ Resolution by Flickr user Rachel.Melton
With modern DSLRs, you don't need to know too much more than that, because you can correct for color temperature with your white balance setting. Many hobbyists leave this setting on "auto", but if you want to fine tune it, you can tell your camera that you're shooting in daylight conditions, or on a cloudy day.
Or if you want much greater precision, you can shoot a pure white object and then let the camera use that image to calculate the color temperature of the scene. Some cameras will even let you go a step further than this and tweak the setting by Kelvin value, but this requires a color temperature meter and for most photography it's an unnecessary step.
Even though modern cameras are pretty good at compensating for color temperature, it's important to have a basic understanding of it so you can fine tune your white balance when necessary.
Have you ever sat next to a campfire telling scary stories with a flashlight shining on your face from below? Light from below makes you look scary because we're not accustomed to seeing light that comes from that direction. It's not natural.
Untitled by Flickr user DavidR_
Knowing this should give you a basic sense of why the direction of light is important. You can give your images different impact simply by changing the direction of the light. For example, the long shadows and side lighting of sunrise and sunset can feel dramatic, while backlighting can feel magical or surreal.
The direction of the light, of course, does more than just convey mood. Portraits in particular can appear vastly different when different light directions are used. Frontal light (also known as beauty light) can make a subject appear thinner. Side light from below jaw level will add sparkle to her eyes. Light that comes from above will simulate natural light.
Light intensity is closely related to light quality. High-intensity light sources tend to produce hard light, and low-intensity light sources produce soft light. But for practical purposes, light intensity mostly relates to the aperture, shutter speed and ISO you will need to choose for a particular scene. In a scene with a low light intensity, for example, you may need to sacrifice depth of field in order to achieve a faster shutter speed. In high intensity light, you may have to choose a much smaller aperture in order to slow down the shutter speed. And the intensity of the light will also dictate your ISO - you may not be able to hand-hold your camera in a low intensity scene if you chose a small ISO.
In a studio setting, of course, you have control over light intensity and so you also have the freedom to set up your lighting in such a way that you can use whatever shutter/aperture/ISO combination you think is appropriate. You can't do that with natural light so easily, though you can make compensations with extra equipement such as neutral density filters, reflectors etc.
The properties of light
Now we're getting into the technical stuff, but it's still a good idea for you to have a basic understanding of the following three properties of light: absorption, reflection and transmission.
Light behaves differently when it reaches different objects. Some objects absorb light, others reflect it, and others transmit it (that is, it passes through them). This is in fact how color works: an object that we perceive as red actually reflects red and absorbs other colors. True white reflects all colors, and true black absorbs all colors.
Most objects absorb light. This includes most dogs, cats, brick walls and potatoes, among other things. Objects that reflect light are often those we perceive as shiny, like foil, polished metal surfaces, and freshly fallen snow. Non-shiny objects can also reflect light, though--if you've ever bounced your flash off a ceiling or a plain white wall you know what I mean.
Reflection can be direct or diffused - a direct reflection comes from a smooth surface such as a car's silver bumper, while a diffused reflection comes from a surface that has some texture, like one of those ugly popcorn ceilings circa 1972. As you might guess, a diffused reflection produces softer light than a direct reflection.
Stone alive by Flickr user campra
Objects that transmit light are typically those we can see through, such as clear water or glass. Glass is so perfectly transparent that it doesn't do much to the quality of light--in technical terms, this is called "direct transmission." Its cousin, frosted glass (like that stuff you have in your bathroom) also transmits light, but it diffuses it, which makes it softer. Then there is selective transmission, which happens when the glass is colored. An object that selectively transmits light will only transmit light that is the same color as it is, while reflecting everything else. So the light coming through a green piece of glass will be green, because all other colors are reflected before they reach the opposite side of the glass.
What does this mean for you as a photographer?
It means that you can use these principles to manipulate light in order to improve your photographs.
For example, if you're shooting a subject on a bright sunny day, you don't need to accept that you're going to have to shoot in hard light. Instead, you can use a portable reflector to bounce light into the shadows of your subject's face, which will give you more detail in those shadows. You can also use a diffuser to soften the light, which is a semi-transparent surface placed between your light source and your model. A soft-box serves the same sort of purpose: a diffuser between the light source and the subject keeps the light soft and even.
It's surprising how many hobby photographers don't really understand light, and it's even more surprising how many just don't pay attention. All those auto settings on our DSLRs are both a blessing and a curse--they help take the decision making out of photography, which is great when we're shooting on the fly but can also be a detriment when we want to have more control over our images.
You can greatly improve your photographs simply by thinking about light every time you snap a picture. Whether you are manipulating it, compensating for it, or using it as a focal point of your image, light is the single most important element in any photograph. Ignore it and your images will suffer. Embrace it and you'll find yourself with photographs you won't believe you took yourself.
Also take a look at the Twenty Five Outstanding Uses of Light gallery I assembled for more inspiration.
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