Photography 101: Getting to know your light meter

By Anna Chan

In order to achieve a perfect exposure for a photograph that is not too bright or too dark, it is important to know how the light meter works and what it is telling you. Most modern cameras have an in-camera light meter which will give an ideal exposure when the meter reads zero. Pictured above is an under-exposed reading of light, in other words, not enough light is coming into the camera, which will result in a dark photo.

Older cameras are fitted with light meters listing the f-stops or shutter speeds along the side of the viewfinder. It will display which f-stop or shutter speed you’re currently set at, and tell you whether there is too much or too little light. This is indicated either by a needle or the appropriate value to shoot at.

As mentioned in the first feature, changing the aperture and shutter speed will change the amount of light that hits the film. The appropriate amount of light passing through the lens can be achieved by adjusting the aperture and shutter speed. For example, taking a look below at the three photos of the same scene, different amounts of light give different results. The first is over-exposed, washing out the details in the photograph such as the spokes in the wheels of the bikes. This results from a small f-stop, a slow shutter speed, or a combination of both. Keep in mind that a small f-stop means a big hole, and vice-versa. The second photo is under-exposed causing most of the photo to be underdeveloped hence, very black. A large f-stop, a fast shutter speed, or a combination of the two can cause this to happen. A properly exposed photo will find middle ground between the two, ensuring the brightest spots aren’t too bright and the shadows aren’t too dark.

Cameras are designed to set the focal point to output at 18 per cent gray. Talking black and white film, of course, what you take your light reading off of will print at 18 per cent gray. The effect desired will determine what your perfect exposure is. In the first photo below, I metered off the Prairie Chicken. The curves and reflections show up quite well. These features are printed at 18 per cent gray, permitting the details to be discernible and hence the focus of the photo. The sky in this photo is over-exposed, which causes the detail in the sky to disappear. The second photo was metered off the sky, meaning the camera took a photo where the sky would be perfectly exposed. Metering the sky brought out the details in the clouds, but in effect under-exposed the Prairie Chicken, turning it into a silhouette.

I have aged a month since the first installment of these photo features, but I am still no expert. You are still welcome to e-mail me any questions you may have about the information presented in this feature at

Happy metering.

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