A Short Course Book
Using Your Digital Camera
A Guide To Great Photographs

Introduction to Lenses

 
Point and shoot cameras often have 3x zoom lenses but they can range much higher. This camera from Canon is equipped with a 12x zoom.
 
 
Click for a PDF of Canon lenses.
 
 
Lenses with larger maximum apertures let you use faster shutter speeds and are often called "faster" lenses.
 
 
Click to explore how image stabilization reduces but doesn't eliminate blur caused by camera movement.
Most digital cameras have a fixed zoom lens that can't be removed or replaced. One big advantage is that the camera is sealed so no dust can get on the image sensor. Digital SLR cameras have removable lenses so you can change them when circumstances dictate.

Lens Information

Many lenses display information that is useful in your photography. Be sure to take the time to read it and any printed information that came with the lens.

Information around the lens may include:
  • The focal length of the lens or the zoom range in mm. Here the range of a zoom lens is 6.0-72.0mm. On fixed lens cameras the zoom range is often given as a multiplier. For example, 6.0-72.0mm is 12x.
  • The maximum aperture or aperture range on a zoom lens. A lens' maximum aperture is determined by dividing the actual diameter of the aperture opening into the focal length of the lens. That's why the aperture might change from f/2.8 when zoomed in, to f/3.7 when zoomed out. Larger maximum apertures let you use faster shutter speeds to freeze action, but can add dramatically to the cost of a lens.
  • The size of filters or other accessories that can be screwed into the threads. The diameter is usually preceded with the symbol f as in f85mm.

Image Stabilization

When you move the camera during an exposure, especially at slow shutter speeds, it causes blur in the image. To reduce this blur, some cameras have image stabilization or vibration reduction systems. These systems use a sensor to recognize camera movement and then compensate for it by shifting a lens group in the lens, or shifting the sensor in the camera. When the camera has a fixed lens, it doesn't matter which approach is used. However, on cameras with interchangeable lenses it does matter. If the system moves the sensor it will work with any lens, if it moves a lens group it only works with special lenses.

SLR cameras from major camera companies let you choose from a wide array of lenses. Here are those offered by Canon.


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