When to Over-expose

Bright white or dim light

Your digital SLR camera isn't perfect.

This statement may come as a shock to you if you've just dropped almost $1,000 on a new digital SLR, and expect it to do almost everything except clean the house for you.

But it is a true statement - and I'll explain why in just a moment.

Digital SLR Light Meters

Every digital SLR camera has a built-in guage for measuring light called a light meter.

The light meter gathers information about the contrast in the scene you are trying to photograph, and then chooses a shutter speed and aperture so that the photo will look natural.

If the image appears too dark to you then it is under-exposed and if it's much brighter than you remember then it's over-exposed.

Here's an over-simplification: your light meter is a jack-of-all-trades.

Rather than being a specialist, it has to be able to judge the amount of available light within a HUGE range of possibilities.

In order to ensure that 90% of your photos turn out correctly exposed, the camera always aims for the middle ground when it's trying to determine the right exposure settings.

Middle Ground = Middle Gray

As it turns out, this middle ground has a name: middle gray.

Yes, even when there is color present in the scene that you're photographing, the camera is trying to capture bright and dark areas as a neutral gray tone.

By shooting for middle gray, the camera under-exposes when the scene is very bright, and it over-exposes when the scene is very dark.

In the end, you wind up with a photo that looks natural.

But your camera's need to make everything look gray can have a negative impact on your photos in two situations.

When Your SLR Gets It Wrong

There are two lighting conditions where your digital SLR will wind up underexposing the image too much:

White subjects in bright sunlight
Light subjects in dim shade

Let's start by talking about the white subject in sunlight.

Remember: your digital SLR camera wants to make everything look gray. So can you imagine what happens when you take pictures of subjects that are almost pure white?

Yep, that's right: they wind up looking gray.

The end result here is that your camera detects a bright white subject, and feels that in order to get a good photo it must under-expose the image.

When you underexpose an image that is predominantly white, you wind up with an image that is predominantly gray.

Something similar happens when you're taking photos in deep shade .

Under these conditions, a natural exposure will wind up looking a shade dark if you trust your camera's light meter to judge the exposure.

So what's the photographer who doesn't want to correct exposure with an image-editing program to do?

Intentional Overexposure

We've taken the long route, but we're finally getting around to defining when to over-expose a digital photo.

You'll want to intentionally over-expose when you're taking photos that match the two conditions I've listed above.

Common white subjects that under-expose include snow, sand and any large object that's white - like the Queen Mary II (shown above).

Any subject taken in the shade will tend to under-expose regardless of its color.

Under these circumstances, you are going to override your camera's light meter and instruct it to over-expose the image (as least according to the light meter).

But guess what? Your image is going to turn our correctly exposed since it was under-exposed in the first place!

All you're doing is compensating for the camera's desire to capture middle gray.

How to Overexpose

There are two ways you can over-expose an image:

Set your camera's exposure compensation setting to plus one (+1)
Set the camera to manual mode, and choose a shutter speed/aperture combination that results in the image being over-exposed (according to the light meter)

The first setting is certainly easier, because you can still leave your camera in program mode. Just be careful that you set the exposure compensation back to zero once you're done, otherwise you might over-expose an image that should not be.

The second setting requires more familiarity with your camera's aperture and shutter speed settings, but is easy to set back to zero if you want to.

Regardless of the method you choose, both of these will result in photos (under special conditions) that are correctly exposed when you take the photo - no image editing required.

Of course, if you're still not sure about when to over-expose, then leave your camera in AUTO mode and fire away - but don't blame your camera if the end result looks a tad gray.

After all, it's easy for you to tell what you're taking a picture of, but your camera isn't quite THAT smart...yet.