Should I buy a Prime lens or a Zoom lens?
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.
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.
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.