Upload & Sell: On
I am thinking of getting the 135 with extension tubes to so I can use it as a portrait lens (especially female faces) ... I have a 7D.
... the difference between F2 and F2.8 for female portraits might prove to be more flattering as well as flatten features better with the longer focal length.
If any of you have thoughts on this and even have some images with the 135 both for closeups (stopped down I guess) and for portraits wide open, I'd love to see them and also get your advice.
I'm not sure how a wider aperture would be considered "more flattering" for a face, male or female. It's perspective (a function of distance from subject) that determines whether features appear to be flattened or not; that's what's normally referred to by the term "flattering" in the context of portraits. And 135mm on a 1.6x crop camera is relatively long for portraits; it does indeed provide a flattening perspective. The effects of the wider aperture are narrower depth of field (potentially too much - one does not necessarily always want only the eyes, or even only one eye, in focus) and more separation from the background, with the background (or any foreground elements) blurrier.
I'll see if I can dredge up a portrait or two from the 135 & 40D; if so, I'll post them in a subsequent reply.
I haven't used my 135 with tubes.