When we look at how to understand overexposure or underexposure it’s important to have an overall grasp of what these terms mean.

Overexposure

When a photograph is overexposed it simply means that the photo is too bright. Typically colors will look washed out and highlights will often be “blown out” or completely white.

Underexposure

When a photograph is underexposed it means that the photo is too dark. Often you’ll lose details in the shadow or darkest areas and can often cause them to look black or near black.

Exposure Controls

Almost every camera comes with some sort of exposure control function. If you like to think of light as water (as in flow of information) then you can think of the exposure controls as a valve. This “valve” allows you to control the “flow” of light hitting your film or sensor. The default setting is neutral so that the camera controls as even an amount of flow of light to the sensor as the settings would suggest.

When thinking about the exposure controls as a valve you can control the camera to allow more light or less light than the camera’s light meter would normally suggest.

Exposure Histogram

Most digital cameras allow you to set the viewfinder or LCD to display the histogram either before or after the photograph has been taken.

The black bars in the exposure histogram indicate the distribution of light and dark values.

If your histogram shows a tall clump of bars to the left side of the histogram then your scene is probably dark (to the light meter) and may indicate that the photo is underexposed.

If the bars are tall and clumped to the right then your photo is likely overexposed as the histogram and light meter are indicating an excessive amount of bright area in the scene before the camera.

Not All Scenes Are Created Equal

The average scene will likely have some varying amount of both light and dark areas. You will come across scenes where there simply isn’t a way to avoid overexposing or underexposing an image. There will be times, as well, where you will have areas in one scene were the histogram is indicating both overexposure and underexposure!

There’s nothing inherently wrong with that!

You can have some really dark areas of your photograph or blown out highlights if that’s what you’re looking for as an end result. Remember that photography is a creative pursuit so allow your creativity to push the envelope from time to time.