Russ,
I am aware that most people do street with unobtrusive cameras with widish lenses. But considering that you don't seem to think that an interaction with the subject is needed, I would think that a long enough lens completely removing the photographer from the scene is an interesting option, isn't it? It is of courde impossible to stay un-noticed with such equipment, but it's possible to stay un-noticed from the subject, which is all that matters I would think?
I am also not sure that photographers such as HCB wouldn't have considered this since we now have incredible cameras and lenses making this possible. It was simply not even possible 5 years ago and I like to explore new(ish) avenues.
The look resulting from limited DoF may be interesting too. I love the bokeh generated by this lens accross the field of the image, with fully circular OoF highlights till the border of the image (something you cannot get with shorter tele lenses), the very limited light fall off wide open and the near perfect correction of all chromatic aberrations.
I'll for sure continue to see where this leads me.
Cheers,
Bernard
In Europe HCB almost always used a 50mm. The main reason, I think, is that 50 gives you the closest thing to the perspective of normal vision, and consequently the kind of geometry he was looking for. In the USA he frequently switched to a 35. I'm not sure why. A long lens sounds logical, but I think if you try a shorter lens you'll find that being in the heart of the scene you're working gives you a lot more options and also gives you a better understanding of what's going on. Here's an example. I was practically in the midst of these kids with a 50mm, and by being there I managed to catch the girl looking directly at the tall kid. From a distance I'd have been unlikely to distinguish that, and what I shot would have been compressed -- squeezed down so that the whole scene would have been flat. I had a 50mm f/1.4 on the D3, which isn't what I usually use on the street, but at night the size of the body doesn't matter much and f/1.4 and ISO up to 6400 helps. Yes, a normal lens keeps you from being unnoticed, but you need to learn to do what The Shadow did: cloud men's minds. In other words, you need to learn to be unobtrusive -- just another non-threatening guy in the crowd.
Oh, and backing up a bit, when you say that I don't think an interaction with the subject is needed I assume you're talking about posing. The only guy I know of who did really successful street with posed subjects was Robert Doisneau, though Brassaï's whorehouse pictures called for his subjects to hold still since he was working with awfully slow materials. Some people think posing subjects for street is cheating. HCB probably was one of them. I don't do it, but looking at Doisneau's stuff I can't condemn it.
If you continue with street I think you'll soon love it. Nothing else is like it. Unlike landscape it's never boring, and sometimes it's exciting as hell -- sometimes almost too exciting.