I've been lurking around this forum for a little while now and have noticed that there seems to be little reference to the
value of the various perspective differences provided by different focal lengths. It's almost as if focal length is being used
solely as a framing device rather than as an integral part of the creation of an image.
Perspective within a picture is an important component of its composition, contributing in no small way to the visual and emotional impact. Your choice of focal length/field(angle) of view will always be influenced by the intended use of the image. e.g. web display, magazine illustration (also final size on the page and juxtapositioning with other components), poster displays', publicity hoardings, etc. etc.. So display size and viewing distance are primary considerations in the selection of which lens to to use to achieve the desired perspective within the image.
When it comes to the sharpness/softness of an image, the softening effect of atmospheric dispersion will degrade any image taken with a 'long' lens, whereas a 'shorter' focal length will require a shorter camera-to-subject distance, effectively reducing the atmospheric 'softening'. Of course, the creative use of 'aerial perspective' often benefits from the use of 'longer' focal lengths and the concomitant 'softening'.
Some manufacturers have, in the past, designed 'long' lenses which attempt to minimise the 'blue mountain' effect, but in so doing made them unacceptably 'warm' at nearer subject distances and totally useless in the dry clear air and prevailing 'redness' of desert environments. I've thrown away quite a few.
There's a heap of written material to be found on both compositional and aerial perspective in fine art and photography books and I'd suggest that anyone with a genuine interest in creating pictures (as opposed to merely being an equipment freak) take advantage of both well writtten books and gallery exhibitions of
all forms of art.