Why your camera sometimes gets it wrong
Imagine that everything you saw around you was made of paint. Scoop up all that paint and stir it up, and the resulting gooey mix would most likely turn out to be a boring mid-toned grey.
That’s how your camera thinks. It samples the amount of light and dark it ‘sees’ in a scene and assumes that when everything gets mixed and averaged out the result should be not too dark, not too light. Just a neutral grey. If it averages out lighter than that, then it decides there’s too much light coming through the lens and so it reduces the exposure. And if things average out into a dark tone then it increases the exposure.
Because most scenes contain a balanced mix of light and dark objects, this averaging-out method works pretty well and that’s why the exposure will be pretty much right, more often than not. But what if you’re photographing a scene that only has light-toned things in it? Like for example, a white rabbit on snow.
The camera will ‘see’ white, white and more white and when it averages that all out, it ends up with, you guessed it: white! It decides that just can’t be right because it’s been programmed to think everything should always average out into mid-toned grey. So it reduces the exposure. The result will be a photo that is badly underexposed, with a grey rabbit against grey snow. So now the camera’s happy, but you’re not.
How to fix it
The good news is that your digital SLR (and some of the smarter compacts) will most likely have a function called Exposure Compensation.
At this point you’ll need to look at your camera’s manual to find out how to activate it. Once you know how to turn on that setting in your particular camera, here’s what you do with it.
First of all, you’ll see that exposure compensation is measured in ‘stops’. Stops is a word that refers to your aperture settings.
If your camera keeps making things too dark, you increase your exposure by setting your camera’s Exposure Compensation to a positive number of stops.
And if you want to decrease your exposure you set it to a negative value.
Usually, one stop will make a world of difference to your photo and you can test if you need more or less by taking a shot and glancing at your histogram. If you need help on histograms, a guide to understanding them can be found here.
With a bit of practice in photography, you’ll soon start noticing the kinds of situations where your camera is likely to get things wrong, when Exposure Compensation is needed. The examples below illustrate some of the situations to look out for.
Extremely bright background |