Quote Originally Posted by C. G.
The word "equivalent" really only applies to the angle of view, but not perspective or depth of view. So I guess this makes it virtually impossible to get any real background blur since when shooting portrait you usually don't go over 135mm or at most 200mm, meaning the real focal length you are using is really about 30mm or so, even if you open the lens all the way to F2.8 there should be hardly any blur, am I right?
Absolutely 100% correct. You'd be surprised how many people don't "get" this...

Wide apertures are a good way to reduce the depth of field (DOF), but so are long lenses focused close. The longer the lens, the closer you'll have to focus, and the smaller DOF you'll have - even at a moderate aperture like f5.6 or so. Depending on what kind of portraits you want to do, a 70-200 might be too long. It would be great for headshots and maybe waist-up (technical term? ) but you would have to be a long ways from your subject for full length.

I have a Tokina 28-80 f2.8 ATX PRO and it's a very sharp lens. It's fairly big and heavy but it was a bargain used ($250 or so). There are several versions of this lens, and this one (not the 28-70 versions) is the best one they have. Keep in mind the angle of view will be fairly narrow on a DSLR with a 1.5 or 1.6 crop factor, so this might be a good one to look at for a lot of situations.

Usually when I hear people talk about Bokeh, they're also talking about the quality of the Bokeh too. This has to do with how background out-of-focus highlights are rendered, and generally how smooth everything looks. Some lenses are better than others, and Leica lenses are pretty much legendary in this regard. Nikon's 85 f1.4 is great too but their 50 f1.4 looks nothing like it (current version, older ones are better here). Generally (but not always), primes do a better job but some zooms are pretty good too. The Tokina lens I mention is decent in this regard, but nothing like the 85 f1.4.