Essential Guide to Wideangle lenses
There are three main types of wideangle lenses and these are wideangle primes, wideangle zooms and fisheye lenses. Wideangle primes have fixed focal lengths, which make them quite specialist pieces of glass, but with a simple optical construction and fewer lens elements they're well known for excellent image quality and sharpness. What's more they tend to be typically faster than wideangle zooms and feature maximum apertures as fast as f/1.4.
Wideangle lenses are popular with many different photographers, including those who shoot landscapes and architecture. For these subjects it's handy to have a wideangle prime if you're going to be working in low light and are going to be shooting handheld, but shooting with a wideangle prime at its maximum aperture can increase the risk of optical discrepancies, such as vignetting and a lack of edge sharpness showing in the final image. To bypass any lens flaws and increase the depth of field it's standard practice to close the aperture, which has the effect of maximising image quality and sharpness. Wideangle primes are therefore quite unique and they're often considered to be more restrictive than wideangle zooms.