Danny Hartley writes, "Photography is all about capturing light on a photographic emulsion or electronic sensor. And as such the lens and film or sensor, are the most important components affecting image quality. Essentially, the camera itself is just a light-tight box with a shutter! A camera that allows you to change the lens will obviously give you the greatest flexibility to pick the appropriate lens for the situation. An ideal camera like this is the SLR. You can choose from super wideangle to super telephoto. Macro for close ups. Bellows for even closer close up. Attach it to a microscope. Attach it to a telescope
PRIMES VS ZOOMS
Prime (fixed) focals have the advantage of being fast (bright) and very high quality by virtue of the fact that they can be designed just for that focal length. A zoom lens allows a choice from a continuous range of focal lengths. They are useful where you require a range of focal lengths but want the convenience of a single lens, whether for weight (only one lens), always being ready to take the picture or shooting in a dusty environment and you want to keep debris entering the camera to a minimum (you also need to think about how to change films).
This all sounds great but there are drawbacks. Zooms are slower than primes (smaller minimum aperture) and can thus make hand holding and focusing (whether manual or auto) problematic. Also due to their complexity zoom lenses suffer from more abberations than primes. Lenses from the major camera makers tend to be very good. Third party zooms vary considerably. Like everything else, you tend to get what you pay for.
Zooming is more than just getting closer. It alters the focal length and affects the perspective and depth of field of the picture. Consider whether you should zoom in and use a longer focal length, or get closer and use a shorter focal length?