Originally posted by clackers I've used everything from 24mm to 200mm for portraits. Newer lenses can do the backgrounds better because they tend to have nine aperture blades - rounded, too.
Well, as we're talking about "portrait lenses", I guess it makes sense to answer a simple question. Is shooting "people" (street photography, travel photography, candid shots, etc) the same thing as taking "portraits"?
IMO the answer is no.
Taking portraits, either in studio or with available light, usually involves esthetic and technical choices that are very rarely available shooting candid pictures.
For example most of the times we have time, a luxury that is seldom given, shooting street pics.
If we are given such freedom, it's better to make full use of it, choosing the best tools, not the most practical.
If there is enough time to set up the shots, and choose the best lighting, there is also time to take care of accurate manual focusing and use optics that give the most pleasant images.
According to my taste, the best choice is almost always the kind of lenses I mentioned in my previous post: a fast 85mm/105mm-ish with a smooth rendering, preferably shot wide open.
If I succeed focusing on the closest pupil, I don't mind if the ears are slightly out of focus. A nice background rendered as a mellow palette of shapes and colors is more important.
This is why I think that the number/shape of diaphragm blades is a bit overrated. If I shoot wide open, the hole is always round
BTW, some of my favorite lenses for portrait use have 15, 16 or even 18 diaphragm blades. It was quite common before the "auto" generation with return springs.
To each his/her own.
The desired result calls for specific technical choices. If the picture has to evidence the wrinkles on an old man's weathered face... forget about everything I have just written!