In article <3229D30A.2C2@mit.edu>, kmmalek@mit.edu says...

>If there is no difference in what part of the picture is in focus, is it
>possible to have differences in how the out-of-focus part looks?

(I am assuming that you mean under identical conditions of subject,
direction, framing, lighting, focus, and aperture...) Yes, different
lenses can render the out-of-focus areas differently.

>I was recently looking at an article in the British Journal of
>Photography in which a Hasselblad system was compared to a Mamiya (I
>think) system. One of the points of comparison was the performance of
>the lenses on these cameras, and specifically, how they differed in
>rendering the out-of-focus part of an image. I can't recall if this was
>tied to the different levels of sharpness between the two lenses, but it
>was clear that in one case, the out-of-focus part was more muted than in
>the other.

I prefer the contrastier, snappier out-of-focus rendering, myself....
(I doubt that the OOF [;-] rendering type indicates much about the
sharpness of the in-focus image, though.)

>Is this related at all to "Defocus control" or "soft focus" lenses? How
>do these work anyway?

I think the "defocus control" lenses may allow adjustment of this characteristic, but "soft focus" lenses are a different matter.
BTW, I disagree with this:

>Bill O'Neill wrote:
>>Depth of field depends on only two things; magnification and aperture. [..]

It also depends on lens sharpness, with the less sharp lens having more apparent DOF (the out-of-focus rendering type can also influence DOF,
since DOF is basically an illusion of sharpness).
Hope This Helps