Sunday, January 24, 2010

Making your day Brighter (or Darker)

For many of us in the Northern Hemisphere, we are in the depths of winter. Some of us wood like to sit by the fire and toast our toes. But many of us would like to get outside and make images from the winter wonderland outside.

There is an important thing you should know how to control with your camera - exposure compensation. First let's cover how your camera decides on the exposure level to use and its shortcomings and then a few ways that you can compensate.

The human eye and visual systems of the brain are amazing at being able to adjust to a huge range of light levels without us even being aware of what is going on in our own skulls. Our cameras are not nearly as intelligent.

When you press the shutter button (or half-press it on some cameras) it takes a sample of the scene before it. But it doesn't know what is supposed to be a bright object in shadows or a dark object in a bright patch of sunlight. All it can see an average level of light. In fact, smart people have decided that, on average, the world is 18% gray, and camera manufactures have used that knowledge when build your camera. Your camera assumes that what ever it is seeing is 18% gray. Most of the time it is a pretty good assumption but there are circumstances when it is not.

Back to our snowy days out side. Snow is supposed to be white. (Bonus tip: Don't eat yellow snow).  But your camera doesn't know that, so when you snap the picture of a snowy white scene, your camera sets the exposure based on the assumption that what it is seeing is 18% gray, but it is wrong. It is much closer to 100% white. So your beautiful white snowscapes turn out a dull gray. If you have some of those already you can help rescue them by boosting the photo's exposure level on your computer, but that can only fix so much. The best way to fix it is before you push the shutter button.

There are several ways to approach this, and you will need your manual to figure out how to do it on your camera.

Method 1: Some cameras have a special scene mode for snow, or maybe 'sun and sand', these modes are essentially giving your camera a hint that it needs to use a different set of assumptions about what you are taking pictures of and should give better results than the default mode - if they assumptions a better.

Method 2: Exposure Compensation. This control allows you to tell the camera that the subject you are interested in is brighter or darker than default behaviour would assume. It usually works by speeding up or slowing down the shutter speed. For snow, one to one and a half stops would be in the right range.

Method 3: Go manual, if your camera offers a manual mode and for snow set your shutter speed to a slower level than you camera meter advises.

Today's Assignment: Grab your manual and read up on the special scene modes. Is there one that applies to snow scenes? Figure out how to use it. Go outside and give it a try.

Advanced Assignment: Figure out how to use exposure compensation and go outside and experiment.

P.S. Don't forget to return your camera to default settings after the assignment.
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