Four Secrets About Light and Flash

Photography, it's often said, is "painting with light." In fact, understanding how to use ambient light and your camera's flash is generally the best way to improve your photos, since you can do everything else right, but if the light is wrong, you won't like your photos. I've written about using your flash before--such as "Two Ways to Freeze Action With Your Flash." This week, let's focus on five critical tips for getting better photos with light and flash.

1. The More Diffused Your Light Source, the More Pleasing the Light

I'll call this the First Law of Lighting--in fact, I'd say that it's the fundamental principle behind most of the advice you hear about lighting a photo.

No doubt, you've heard it said that you should shoot on overcast days, or wait for the sun to pass behind a cloud. And you know that you can get better results when you bounce your camera flash or use an adapter that diffuses the light. These techniques are leveraging the First Law--a broader or larger light source will create a softer, more attractive light on your subject.

A narrow light beam, such as from your flash or the sun (which is admittedly much larger than the earth, but narrow from the camera's perspective) is hard light that makes for sharp shadows and high contrast. But if you diffuse that light over a wider area--making it big and broad--you soften the light and reduce the contrast. That's usually more pleasing to the eye. Knowing (and applying) this one fact about light allows you to transform your photos, because now you know that diffusing or broadening narrow light sources will generally de-harshen your photos, ease shadows, and make subjects look more attractive.

2. The Farther Away Your Light Source, the Less Effect It'll Have on Your Subject

That might sound obvious, but there are two subtle details worth pointing out. First, thanks to the laws of physics, it turns out that the brightness diminishes as the square of the distance. If a light is 5 feet away from your subject and you move it to 10 feet, the subject will have a quarter of the light that it started with. In photography terms, that's a two-stop change in exposure.

Second, moving the light will have little-to-no effect on the background, assuming that the background is a fair distance away from the subject. So suppose that you're taking a photo outdoors. You can move the light closer or farther to change the relative exposure of the subject, but the background will expose the same either way as long as you keep the camera settings the same. That's liberating to know, because it means you can fiddle with lighting placement without worrying about what's going on behind the subject.

3. Light Has Color

Light isn't the odorless, colorless substance it seems to us humans. (Okay, light is odorless, but that's beside the point.) Light has a definite color associated with it, and this is known as color temperature, measured in degrees Kelvin. Your camera has a color temperature control, also known as white balance, which most people tend to leave on Auto. But depending upon your camera, you can probably also choose to dial in a specific temperature setting or pick a lighting mode, like Sunset, Overcast, Tungsten, Florescent, or Candlelight. Here's a quick guide to some of the most common settings:

  • Twilight = 12000
  • Daylight shade = 7500
  • Overcast = 6500
  • Early morning or late afternoon = 4300
  • Sunrise and sunset = 3000
  • Candle light = 2000

If you notice that your photo has a color cast after it's on your PC, you can use the color temperature or white balance tool in your photo editing program to fix it.

4. Your Camera Flash Causes Red Eye

In low light, your subject's eyes are fully dilated to allow them to see better. When your flash goes off, the light reflects off the red retina in the back of the eye, giving the eye that signature demonic glow. Note that the only reason red eye happens is because the flash is so close to the camera lens--the light travels to the eye and reflects straight back, which gets caught by the lens. That means there are a few ways to avoid the red eye effect:

  • You can avoid shooting in dark situations.
  • You can turn off your flash and rely on ambient light.
  • You can put some distance between the flash and the camera lens.

Digital SLR users often rely on that last option, since you can hold an external flash in your hand, mount it on a flash bracket, or even bounce it off a wall or ceiling. Read more about this in "Avoid the Red Eye Effect."

Hot Pic of the Week

Get published, get famous! Each week, we select our favorite reader-submitted photo based on creativity, originality, and technique.

Here's how to enter: Send us your photograph in JPEG format, at a resolution no higher than 800 by 600 pixels. Entries at higher resolutions will be immediately disqualified. If necessary, use an image editing program to reduce the file size of your image before e-mailing it to us. Include the title of your photo along with a short description and how you photographed it. Don't forget to send your name, e-mail address, and postal address. Before entering, please read the full description of the contest rules and regulations.

This week's Hot Pic: "Hood at Night" by Edmund Devereaux, Portland, Oregon

Edmund says: "I took this photo of Mount Hood before the start of ski season, when the only lights were the ski lodge at the bottom of the image. I used my trusty tripod and my Canon EOS 50D with the mirror locked. I used the self-timer to trigger a 30 second exposure."

This week's runner-up: "Sunset at the Dock" by Eric Hoar, Springvale, Maine

Eric took this photo with a Panasonic Lumix DMC-ZS5 at the end of a work day at Perkins Cove in Ogunquit, Maine. "The light from the nearing sunset was very strong and was striking the lobster boats full on from the sides," he says. "I underexposed by 2/3 stop and then adjusted the overall light level, brightness and contrast, and saturation on the PC."

To see last month's winners, visit our January Hot Pics slide show. Visit the Hot Pics Flickr gallery to browse past winners.

Have a digital photo question? E-mail me your comments, questions, and suggestions about the newsletter itself. And be sure to sign up to have Digital Focus e-mailed to you each week.

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