Originally Posted by
xpatUSA
If forced to use just one word, I'd say "contrast". If allowed two, I'd say "detail contrast".
As has been said, lighting is very important to get maximum detail contrast from a scene. Think about a row of gravestones, where you want the writing "crisp and sharp" . . where should the sun be? Would you shoot on an overcast day? In other words, both the angle and the quality of the lighting is important for good scene detail contrast.
Another issue is the lens setting, the aperture of which should be set within that magic area between those wide-open aberrations and the onset of visible diffraction. That would be between f/4 and f/8 for many lenses.
In post-processing, there are many "secrets". For ultimate crispness, one secret is to combine more than one radius of unsharp masking, say 3.3px with a low amount followed by 0.3px with a much higher amount. Another secret is to use a more advanced form of sharpening, such as de-convolution. One more secret is to use something like 'Contrast By Detail Level' (RawTherapee) where contrast can be adjusted separately according to levels detail size. And then there are those fancy sharpening plug-ins that many people swear by.
So as not to get disheartened, do remember that the "raw image" (sorry, George) out of most sensors is quite blurry and does need work . . . .