This has to be one of the most asked questions here on the Forum. There is already a lot of information in threads out there, just move your cursor up to the search box and type in "wide angle lenses". Having said that, here are some questions that you really need to ask yourself - as only you can answer them:
- Zoom or Prime? - What type of lens do you think you want?
- Rectilinear (normal) or Fisheye? - You probably are looking for a Rectilinear, but it is always worth asking. Fisheyes are usually 180 degrees wide (Field of View) diagonally corner to corner.
- How wide? - Zooms go down to 8mm (112 degrees FoV), 10mm (100 degrees FoV), 12mm (90 degrees FoV) while Primes are at 14 (81 degrees FoV) and 15mm (77 degree FoV). FoV calculated from Angular Field of View Calculator. Also this question also essentially asks how much distortion are you willing to have? The wider the Field of View the more distortion you are going to get, especially along the edges.
- Sharpness & Resolution - As you put wide angle lenses on your camera body, the shorter the focal length, the more view or information you are focusing on the sensor. The sensor is not getting any larger, so each pixel will be representing an ever larger amount of area. This will lead to reduced sharpness. For instance, a image from a 85mm lens will be sharper than an 8mm lens. However the 8mm lens will have a much wider view than the 85.
- How much do you want to spend? - There is wide angle and ultra wide angle. The wider the lens the higher the price. It takes a lot of optical engineering, fine quality optical glass, and manufacturing techniques to build a wide angle lens. The wider the lens the more view along the edges (top, bottom and sides) it needs to pull into the lens and then bend the light and get it aligned so as to hit the sensor.
- Physical Size - Most of the zooms can be somewhat physically large. The primes tend to be small (for a f4 aperture) and larger for a faster f2.8 aperture.
- Aperture - Most of the wide angle lenses tend to be somewhat slow - f4+. To get something faster you go to a f2.8 prime or a fisheye that tends to be faster.
For the most part your choices are going to be from:
- Pentax - Pentax has the DA 12-24/f4 - a good lens, noted for its well controlled distortion. It is large. Pentax also has 2 primes the DA 14/f2.8 and the DA 15/f4 limited. Pentax also has the DA 10-17 Fisheye. The Pentax lenses tend to cost a bit more than the rest....
- Sigma - Sigma has several zooms, the 8-16, 10-20, and a 12-24. The problem with Sigma is getting a good lens. Once you find a good lens (with out problem), folks really like them.
- Tamron - Tamron has a 10-24 that folks also like. It is well priced, and they appear to deliver lenses that work well out of the box.
After having written all of this - I am going to assume that you are looking for a moderately priced zoom, and your choice will probably be the Tamron 10-24.
I would suggest scooting over to the lens clubs and taking a look at what the various lenses produced in terms of images.
Also, here are a few links on wide angle lenses:
Last edited by interested_observer; 08-16-2012 at 05:58 PM.