I asked my pal Thomas Hawk to answer this question about “getting results with with the right lens (Prime vs Zoom, f-stop and how it affects choices?”

I’d say that personally I much prefer primes over zooms.  I find that not only are they much faster and thus able to be used more effectively in lower lighting scenarios, but that I’ve found them to be much sharper than zooms.  I believe that the 135 f/2 prime lens is the sharpest lens that Canon makes.  It’s also my favorite lens personally speaking.  With bigger apertures (lower f-stops) especially, the depth of field on photos using a good prime with a low f-stop can yield remarkable results — big rich creamy bokeh*  Here’s an example of what I mean using the 135 f/2 at f/2.

* Bokeh: subjective aesthetic quality of out-of-focus areas of an image projected by a camera lens.

The biggest disadvantage with primes of course is that they are very inflexible in terms of framing shots.  You have to move your feet physically instead of the lens.  Also because the fixed focal lengths are so rigid often times you cannot get the shot you want need with the lens on your camera.  This means often times carrying multiple prime lenses with you when you shoot which is a pain and having to change lenses a lot.  Changing lenses a lot also increases the chance that you get dust and other impurities inside your camera and especially on your sensor where it shows up on your images.  I’m fighting a constant battle with dust in my Canon 5D M2 and have with all of the Canons I’ve owned.

So there are pluses and minuses to zooms vs. primes.  I’m not sure there really is a 100% correct answer or that either are really better one than the other, but for me I typically use primes because I’d rather have faster sharper lenses than the flexibility provided by comparable zooms.  Of course bottom line is that whatever you use is only good as what you are able to see with your eye in composing and taking the shot in the first place.

Tom