Should I buy a Prime lens or a Zoom lens?

If you had bought a single lens reflex (SLR) camera a few years ago and asked for a lens to go with it, you would have been handed a 50mm standard camera lens. It is still very much a camera lens that every photographer should have. The optical quality of a good 50mm is superb and they offer excellent value for money as they are cheaper in comparison with long lenses and zoom lens. They are small and light to carry around and the fact that they have a 'fast' maximum aperture means that they handle low light situations better than their zoom or long lens counterparts. The other point worth noting about a 50mm lens is that in terms of focusing it sees objects in a way that is very similar to the human eye.

Lens Popular focal lengths for a 35mm camera
Wide-angle 18mm, 20mm, 28mm, 35mm
Normal 50mm, 55mm
Telephoto 90mm, 135mm, 200mm, 300mm upwards

Today the standard camera lens to be sold with a SLR seems to be a 28-80mm zoom lens. The benefits are obvious as it can be considered as three prime lenses in one (Wide angle - standard - small telephoto). I can feel the traditionalists wince with that one! Not only does that make you budget go further, but there is less to carry and within reason you are always ready for your next shot. The fact is that the quality of zoom lenses in particular has improved dramatically over the past decade. One point that the traditionalists make that is worth taking note of is that a zoom lens can make you less likely to make the most of your camera. Well this is debateable! Always get in as close to your subject as possible rather than letting the zoom do all the work.

Lenses (designed for digital or not) are marked by their actual focal lengths.

The digital sensor in your digital camera.

What changes in digital cameras is the angle of view (apparent magnification or crop factor), which is depending on the sensor size that the lens is projecting on to it.

Sensor sizes currently have many possibilities, depending on their use, cost and
preferred portability. The relative size for many of these are shown below.


The Canon's 1Ds/1DsMkII/5D and the Kodak DCS 14n are the most common full frame sensors. Canon cameras such as the 300D / 350D / 10D and the 20D all have a 1.6X crop factor, whereas Nikon cameras such as the D70(s) and D100 have a 1.5X crop factor. The above chart excludes the 1.3X crop factor, which is used in Canon's 1D series cameras.

Camera phones and other compact cameras use sensor sizes in the range of > 1/4" to 2/3". Olympus, Fuji and Kodak all teamed up to create a standard 4/3 system, which has a 2X crop factor compared to 35 mm film. Medium format and larger sensors exist, however these are far less common and currently prohibitively expensive.

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