--- "Kotsinadelis, Peter (Peter)" <[EMAIL PROTECTED]>
wrote:
> While I do not look specifically for bokeh I do
> look at the number of aperture blades and roundness
> of the aperture of a lens.
The roundness of the aperture (the diaphragm, really)
only affects the shape of out-of-focus specular
highlights, which is a small part of bokeh. The main
factor is how the lens formula balances various types
of aberrations; this has a greater effect on the
"creaminess" of the blur. (ie, the distance over which
what an otherwise "hard" edge between 2 colors
transitions, and how smoothly this happens.) It is
ASTOUNDING to what this will do to a hard shadow on a
nearby wall from on-camera flash.
As has been pointed out, the shape of the diaphragm
has no effect when the lens is wide open, which is
probably most of the time in a portrait situation.
It's interesting that this topic comes up here,
because there has been quite a debate raging on the
MF Nikon list about which portrait lens is "best". I
really love my old non-AI 105mm f2.5 P Nikkor; but the
Canon 100mm f2 EF is pretty darned close (just picked
it up a couple of weeks ago, cheap!) Both lenses have
6-blade diaphragms, and both have what is in my
judgement, lovely but different bokeh.
MadMat
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