Focal Length

Focal length relates to how close an object will appear when viewed through the viewfinder. It is a measure of how 'zoomed' a lens is. The focal length is measured in millimetres and the higher the number, the more 'zoomed' a lens is.

Lenses with a short focal length are referred to as wide angle, while lenses with a long focal length are referred to as telephoto.

The easiest way to describe this is using a couple of images. Both of the below images were taken from the same position.

The picture on the left was taken using a focal length of 35mm, while a focal length of 420mm was used for the picture on the right hand side.

Most film and digital camera focal lengths do not tie up exactly. This is due to the different size of the recording media - film and electronic sensor.

If you are buying your first camera, this is not really an issue. But, if you are used to a certain zoom with one type of camera, it may take some time to adapt your style of shooting when you change. This is not a problem, just something to be aware of.

The following table outlines how different focal lengths are generally referred to:

When taking pictures, focal length can have a great effect on how they appear. Wide angle lenses generally create more distortion.

This can be a problem when using a wide angle lens to take portrait photographs. It is better to use a longer focal length to create a more representative picture - 50 mm and above is fine. Of course, the other side of the coin is that the distortion can create great effects within pictures and can be used creatively.

Zoom

A camera that has a zoom allows you to fill the frame of a camera with your subject matter more creatively and conveniently. Zoom basically means that the camera has a range of focal lengths that can be used; the camera can zoom into an image to capture a distant object, or more detail.

Zoom when referring to film cameras is normally described by the limits of the focal length, for example 35 - 110mm. With digital cameras the zoom is normally described using the multiplication factor that the zoom lens can create. For example, many compact digital cameras come with a 3x zoom. This is often backed up by a description of the equivalent millimetre values.

The Konica Minolta Dimage Z3 camera for example has a 12x zoom, which is equivalent to 35 - 420 mm of zoom. This is known as a super-zoom camera as its range of focal lengths is so large.

Some cameras have a stepless range of zoom; that is, they can be zoomed to any point within their focal length range. This is particularly true of cameras like SLR's that have a manual zoom system. Most compact cameras however, have a stepped system of zoom. Commonly this will mean that the zoom can be set to the extremes of the focal length range and then perhaps 4 or 5 positions in between. This is fine for most situations.

Cameras with a zoom have a variety of advantages. The zoom can be used to take pictures of subjects that are behind railing, or inaccessible. They can be used to remove a distracting area of a scene by zooming past it, and they can be used to photograph people or animals in natural situations without having to get overly close to them.

A wide angle lens will create a sense of space within an image, while zooming in, will compress the foreground and background of a scene making objects appear closer together than they are. These two facts can be used to good creative effect.

As mentioned in the 'focal length' section, wide angle lenses can distort. This means it is a good idea to zoom a little before taking pictures of people, or they may not be too impressed with the results - enlarged noses and chins are a common result.

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