Essential Guide to Wideangle lenses
The key advantage of choosing a wideangle zoom over a wideangle prime is that they offer more control and convenience when composing an image. With a wideangle prime you might find yourself moving back and forth to frame an image as you want it, whereas with a wideangle zoom it gives you much more flexibility. Optically, the best ones are on a par with wideangle primes; they're not usually much bigger in terms of size and they can often cost a lot less, which seems strange when they're generally more versatile.
There's a great selection of wideangle zooms available for both full frame and APS-C formats, including many alternatives from third-party manufacturers. However, you'll want to carefully consider the focal length before committing to buying one. Choose the wrong type of wideangle zoom and attach it to the wrong camera body and you could find any lines or curves in an image are over-exaggerated.
For full frame DSLRs a wideangle zoom covering a focal length between 14mm and 35mm is usually best, and for APS-C DSLRs a lens with a focal length of roughly 10-20mm will provide a 15mm to 30mm full frame equivalent. Look for a wideangle zoom with a wider focal length than the suggestions above and you'll find your images become heavily distorted and any horizontal or vertical lines will appear curved, which is commonly known as barrel distortion. Usually this type of distortion is most obvious at the edges of the frame or when the camera is tilted upwards which can accentuate the way a lens perceives straight lines.