One literal approach to photography is “f/8 and be there”—be ready, be at the scene, and make everything “sharp”. Strangely enough, this long-standing idiom makes a lot of sense for today’s high resolution digital SLRs, where stopping down past f/8 degrades image contrast and sharpness (see Diffraction).
But assuming one is “there” and the subject matter is placed as desired (the “composition”), what other factors bear on the result? Certainly lighting plays an enormous role, but so does depth of field; it is the visual impact and perception of the composition that changes as a result of these secondary factors. Consider the two images below; one is shot wide open at f/2 and the other is shot at f/8 (handheld, framing is not exactly the same). Which do you prefer?
Nikon D3 + Zeiss ZF 28/2 Distagon, f/2 (left), f/8 (right)
If you belong to the “everything sharp front-to-back” camp, you’re going to be annoyed at the f/2 image, and still be annoyed at the f/8 image, since even f/8 cannot provide enough depth of field to render more than a narrow band of sand crisply. A good friend of mine will find the f/2 image distasteful (“it’s blurry”), but I prefer it.
The Zeiss ZF 28/2 Distagon offers great artistic possibilities at f/2 (for several different optical reasons). By comparison, an f/2.8 lens has 1.4X the depth of field of an f/2 lens, and thus loses such expressive potential. This is one reason that I wish Zeiss had made the 25/2.8 Distagon an f/2 design instead, and why a 20/f/1.4 would be appealing.