OVERVIEW
A lens is generally considered to be "wide angle" when its focal length is less than around 35 mm (on a full frame; see camera lenses: focal length & aperture). This translates into an angle of view which is greater than about 55° across your photo's widest dimension. The definition of ultra-wide is a little fuzzier, but most agree that this realm begins with focal lengths somewhere around 20-24 mm and less. On a compact camera, wide angle is often when you've fully zoomed out, however ultra-wide is usually never available without a special lens adapter.
Regardless, the key concept is this: the shorter the focal length, the more you will tend to notice the unique effects of a wide angle lens.
What makes a wide angle lens unique? A common misconception is that wide-angle lenses are primarily used for when you cannot step far enough away from your subject, but yet still want to capture all of this subject in a single camera frame. Unfortunately, if one were to only use it this way they'd really be missing out. In fact, wide angle lenses are often used for just the opposite: when you want to get closer to a subject!
So, let's take a closer look at just what makes a wide angle lens unique:
- Its image encompasses a wide angle of view
- It generally has a close minimum focusing distance
