I did something incredibly stupid while shooting a black tie event for a company last year. I totally forgot my 70 200mm f/2.8, so I had to shoot with a short 50mm lens for the candids while the guests had dinner. To get a decently tight shot with a 50mm lens in this situation, I needed to be about 5 feet from the subject. It was a failure. Everyone froze up and looked terribly uncomfortable when I got that close with my camera. I couldn t get any decent candids that way and it ruined the shoot. Personally, I shoot most of my portraits at 100mm or more unless it s a full body shot, in which case I shoot at about 70mm.