Types of Digital Camera Lenses

We are going to examine now the lenses according to the criteria of the angle they cover. Although an angular in 6 x 6 format doesn't have the same focal length as the equivalent in universal format, the considerations for both are identical.

Normal Digital Camera Lens

Usually, cameras are equipped with a fixed normal focal lens or with a zoom of focal lengths around normal. In 35 mm, the focal lengths that give us an angle of vision similar to the eyes, go from 40 to 55 mm (typically 50 mm). This implies that the objects occupy an angular space in the image equal to the one they occupy in our field of vision; the representation of the three dimensions of space (perspective) is also similar. If we look through the viewfinder of a reflex camera with a normal lens, and at the same time open the other eye, the impression the image in the viewfinder gives us is somewhat similar to looking through a rectangular window which limit's a portion of our total field of vision. In this field, the objects appear to be the same size as at first glance. The normal lens offers a version of the scene just as it really appears, with a natural perspective and without the objects appearing reduced or amplified. This “human vision” is the preferred by many of the great photographers because it provides a clear idea of what the scene really is in relation with the spectators situation. It is an almost essential, it's easy to use, the cheapest and almost always available in many luminance (and prices). For these reasons it is the most widely used lens.

Telephoto Digital Camera Lenses

Over the focal considered normal, the angle of vision of the camera is much narrower, and therefore the image covers a smaller visual field than the eyes. If we look through eh viewfinder of a reflex camera with a telephoto and keep the other eye open, it no longer looks as if we're looking through a window but through a telescope. We can't superimpose the viewfinders image with the eyes because the framed objects occupy a larger angle than in the eye, the are amplified . Since the lens provides images of a larger size, it produces a sensation of “getting closer”, which is nothing but a simple enlargement of part of our field of vision without moving from our place. The angle of vision get narrower the greater the focal length. We can subdivide the lenses in three categories:

Short (from 70 mm to 200 mm in universal format).
Medium (from 200 mm to 400 mm).
Long or super telephoto (from 400 mm to 2,000 mm or more).