The Normal lens (updated)

When I bought my first camera in the seventies, zooms were expensive and not very good, and there was no such thing as a kit zoom lens, one sold with the camera in a bundle. (I think Fuji came out with the first one in the late seventies.) But since then, zooms have become better and cheaper, and everybody wants them. But there are still reasons to use prime lenses, such as cost, weight, size, and fidelity. Even the cheap 50mm lens can be surprisingly good and versatile.


It should be noted that on a DSLR camera (unless it's an expensive full-frame one), a 50mm lens is no longer a "normal" lens, it's more to be regarded as a shortish portrait-length lens.

Of course not all 50mm lenses are equal. For example, one of the first lenses I got when I first aquired a good digital camera (Nikon D100, back in 2002) was Nikon's 50mm 1.4. But unfortunately my dreams of creamy soft backgrounds were dashed by that lens's dreadful "bokeh", meaning the blur is uneven and edgy, not smooth. In contrast, I recently got Pentax's 50mm 1.4 AF lens, and it has beautiful bokeh (and is sharp too).

Nikon 50mm at 1.4:

Pentax 50mm at 1.4:

... One should note that bokeh is very subjective, and also changes a lot with the light, with distance, with the kind of detail in the background, etc...

Update: Steve said:
As for bokeh, just watch for the number of blades in the lens. More is better as a general rule.

That is true. Because except for full aperture, with spot-shaped out-of-focus highlights, one will see the shape of the diaphragm in them, and most find a circular shape best.
But: another important factor is whether a point-shaped source of light gives a disc of light with more light in the center as is natural, or more near the edges. The latter often happens with lenses with aspherical elements, and tens to give edges within the blur, and to make "double lines" of edges in the blur.