When I shoot environmental portraits, I usually place my subject off center. However, I've seen instances where the photographer has intentionally centered their subject. Here is an example: http://lightbox.time.com/2012/02/07/the-life-of-lucian-freud/#1 Personally, I would have framed it so the person is not in the middle in order to create some tension and dynamic balance. What is your opinion as to why the photographer would have centered the subject in the attached example? What are some instances when using the center of the frame is a better compositional choice?
Whenever it makes sense to. The "rules" of composition are not rules at all, and many of them are derived (sometimes tortuously) from examining pictures that people have found pleasing for one reason or another. That there are so many "rules" to choose from is an indication that there are many, many different ways to create a picture that is either pleasing to the eye or tells the story you want to tell. It's nice to learn the various rules, but don't take any of them too seriously. (And leave the art critic vocabulary to the art critics -- they can see things that no ordinary, reasonable person can, or at least come up with a scientific-sounding explanation of why a good picture is a good picture, even if it means making up a new compositional rule.)
When you stand in front of a mirror to shave... do you stand centered in mirror or do you compose yourself by the rule of thirds?? The point of centering, at least what I am interpreting, in this image is to create the effect that he is looking in the mirror shaving. As though we, the viewers, are viewing from inside his medicine cabinet mirror. And so you decide where to place your subject based on the story you're telling... if there is no extra effect such as mirror view -- then go ahead and use rule of thirds but don't be so bound to rule of thirds (or other rules) that it blocks the creative potential that another composition could serve. Start from the rule, if you like, then ask is there another story I could tell with different placement! No matter what always consider other placement because otherwise you are not even open to the possibilities. Be open to the possibilities!
I agree that this photo may have been more appealing, especially on a subconscious level, if it was off-center. Personally, I would have cropped out some of the extraneous things on the one side in particular. However, the final decision made by the photographer was most likely made simply because it "felt" right. We've probably all done it.
I personally agree that the photo probably would have been slightly more appealing had the photographer shifted the subject from the center. It would have balanced the photo and added a little bit of tension. Generally these are the reasons a composition like this is not framed with the subject in the center.
You can, of course, center the subject in many situations. If your subject is filling the frame, centering the subject often allows either side of them to fall on these 'balancing lines' (thirds, golden ratio). This is aesthetically pleasing.
If your subject is perhaps lying down perpendicular to the camera (on a bench or a couch, for example), having the feet on one side and the head on the other side will feel balanced.
As well, a symmetry in the surroundings of a subject may also allow for an aesthetically pleasing centering of a subject as given by the rough example.
The composition is balanced because of the overall symmetry.
In general, it should come down to what feels right as you're framing your shot. I often find myself "falling" into these guidelines I've talked about in this answer (and other general guides in composing) because they intrinsically feel good. I found these to be pleasing before knowing what they were called or why they are used.
It's about creating an effect, right? Centering the subject and having him face the camera creates a sort of dramatic confrontation with the viewer.
In my mind, if you want the subject to confront the viewer, a centered, full-on view might be appropriate. As noted above - this does't preclude also using the rule of thirds or another composition technique as well.