If anyone is concerned about drawing attention to himself, then better not walk around with two cameras and lenses around your shoulders as I often do. I can't remember the number of times I've been asked by complete strangers why I carry two cameras.
The reason of course is obvious. I get the benefits of a zoom lens of a quality and range that simply cannot be bought at any price. The Nikkor 14-24/2.8 attached to my D700, plus the 24-120/F4 attached to my D7000, results effectively in my having a good quality zoom lens with a range from 14-180mm. That's very useful.
Now it's true that a good prime used in ideal conditions will usually produce sharper results than any zoom, and there's no doubt that a crisp, sharp image with every strand of hair clearly delineated is a joy to behold.
However, if one is walking around, presumably trying to capture the moment, the full sharpness benefits of a prime lens will often not be achieved, unless one excludes all those shots that one knows will likely need cropping because one didn't have the time or opportunity to get oneself into a position and distance from the subject for the best composition.
Now, I admit that I almost always use my 24-120/F4 with the DX D7000 which crops the edges where resolution is sometimes not too good. Edge and corner resolution could be a problem when this lens is used with the D800.
However, let's get things into perspective. The Photozone tests are quite revealing. The 24-120/F4 is sharpest between focal lengths of 24mm to 50mm. Beyond 50mm resolution begins to decline, both in the centre and at the edges.
If one compares the Photozone results for this zoom at 24mm, with the Nikkor AF-S 24/1.4 prime, both lenses tested on the D3X body, one finds the 24mm prime, at its sharpest aperture of F4, is indeed sharper in the centre than the zoom at 24mm and F4. The results are 3784 Line-Widths-per-Picture-Height (or line pairs per picture height) for the zoom, and 3990 for the prime.
The prime is delivering 206 more LW/PH in the centre of the image (extrapolated to the full frame). That's 5.5% more resolution. Wow! I'm so excited.
Let's engage in a bit of basic maths. If I zoom from 24mm to 48mm, I've essentially cut the image in half along both dimensions, resulting in a composition of 1/4th of the area.
If we compare the central portion from both images, where they are both sharpest, the 24mm prime (at its sharpest aperture of F4) will have 5.5% more resolution than the zoom.
Supposing I crop that central portion of the image with the zoom at the time I take the shot, instead of later cropping it in postprocessing. In other words, instead of using 24mm with the zoom, I use a 5.5% greater focal length, which would be 25.132mm. Call it 26mm if you like. Have we not cancelled out that resolution advantage of the 24mm prime?
Maybe we haven't. Maybe there are other considerations and factors that have escaped me. Please feel free to comment.
Of course, I understand there may be other desirable features of any particular prime compared with a zoom, such as a nicer bokeh and a wider maximum aperture for shallow DoF. However, the advantages of VR in a walk-about lens, which many Nikkor primes lack, may often outweigh the advantages of a wider aperture, unless achieving a very shallow DoF is the objective.
I should have added also, that in order to achieve that extra crispness that a prime lens may make possible, one needs a fast shutter speed at a reasonably low ISO. Increasing ISO tends to reduce resolution.
Bernard claims he is able to get sharp results with a prime lens without VR at a shutter speed of 1/2FL. If such shutter speed is only attainable at ISO 6400, then one might have to compare the results at a shutter speed of 4/FL using a lesser quality lens with VR at a lower ISO. In other words, say, 1/400th with a 200mm prime at ISO 6400, as opposed to 1/50th with a VR zoom at 200mm and ISO 800. Which would be better?