The lens is arguably the most important part of the digital camera — after all, it plays the biggest part in making the picture. In principle, the lens of a digital camera works in the same way as your eye, opening and closing its aperture to adjust to changing light conditions. We'll be discussing aperture in full detail in our next instalment of the Learning Centre.
Most compact cameras on the market today will come with a variable focal-length lens (that means it can zoom in and out to get you closer to the action).
Focal length is the distance between the lens and the image sensor when the lens is focused at infinity.
The focal length also helps determine the field of view of a digital camera's lens, or what exactly the camera can see of a scene. As we'll see, the field of view increases or decreases depending on the focal length.
We often talk about the focal length of a lens in three ways, with measurements still left over from the days of 35mm film.
This covers any lens with a focal length of anywhere between 24mm to 35mm. This means the field of view is much wider, and essentially allows you to fit more of your subject in the frame. Super wide-angle lenses are characterised by their focal length being less than 24mm.
A focal length of anywhere between 35mm and 80mm is known as a standard lens. The happy medium is a 50mm lens which lets the camera capture a scene "as the eye sees it".
Lenses that have a focal length of over 100mm are telephoto. You can often tell just by looking at a photograph if it has been taken with a telephoto lens as these images often look like space has been flattened out, with less depth to them than if the photo had been taken with a wide-angle or standard lens.
So how do you know what sort of lens your compact camera has? Often on the lens barrel you will find an indication of the focal lengths, though these will be written in the digital equivalents, not the 35mm equivalent like we've discussed above.
Check your camera manual under lens specifications as they will list the values in 35mm measurements. Most of the time your compact camera will come with a focal length that can vary between 35mm and 105mm. These numbers roughly equate to a 3x optical zoom. You'll find some compacts currently on the market come equipped with wide-angle lenses of 28mm or less.
Digital cameras will come with focal length measurements written on the lens, but they aren't 35mm equivalents. (Credit: CBSi)
A superzoom is what we call a "bridge" camera that looks almost like a dSLR but has no interchangeable lens.
The lens itself varies between an extreme wide angle to telephoto focal length, like on Canon's SX1 IS, which has a lens that extends from 28mm to 560mm.
On a compact camera, zooms usually range from anywhere between 3x to 10x. Extend the zoom reach to anything further and you start to enter into a different range of camera that is called a superzoom, or megazoom, with extreme telephoto lengths.
That said, don't rely on your zoom lens to do all the work for you. Some of the best photographs can be taken by using a standard focal length or what is known as a prime (fixed focal length) lens.
Renowned photojournalist Robert Capa put it aptly when he said "If your picture isn't good enough, you're not close enough."