Photography - The LensWriten by Danny Hartley
Photography is all about capturing light on a photographic emulsion or electronic sensor. And as such the lens, film or sensor are the most important components affecting image quality. Essentially, the camera itself is just a light-tight box with a shutter!
You've seen the wonderful pictures from the rovers sent by NASA to Mars. All detailed and colourful. You might think that they're from some huge megapixel space-age techno-beast and you'd be surprised to hear that the sensor is a paltry 1 megapixel. Bigger pixels mean less noise which is always a good thing, but where NASA put all its money was into a very high quality lens. The results show it was worth it!
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?
FOCAL LENGTHS
Standard Lenses (~50mm)
A standard lens is the usual lens supplied with an SLR. They are good general purpose lenses having an angle of view close to the human eye. They are sharp, compact and lightweight.
Small standard zooms have a range of typically 35-70mm (2x), 28-85mm (3x) or 24-105mm (4x). These zooms often replace the 50mm lens.
A typical compact has a zoom lens with a focal range of 35-100mm.
Wideangle Lenses (