Hi Lex,
Olaf, I wouldn't read too much into the iris-shaped highlights in the
spiderweb photo, particularly the white highlights. Very few lenses can do
better when shooting into leaves against a bright sky. It also depends on
aperture and distance between the subject in focus and the out-of-focus
background.
Before you joined the list we already pretty much exhausted the bokeh topic,
we then came to the conclusion that this particular situation is indeed
about as difficult as it gets. This is why I call it the "bokeh-killer"
test... Nonetheless, with this test one _does_ see a lot of differences
between the bokeh of the various lenses. The 100/2 does a pretty good job at
it, but I've seen some terrible results from the 28/3.5, 50/1.8, 50/3.5 and
the 65-200/4 lenses. Certainly there must be more lenses that do a
relatively good job at it, whereas there will also be some more that do a
relatively poor job at it. Yet, the bad bokeh as shown in Ranjal's picture
is very extreme: I had not yet seen any picture (apart from some taken with
the 50/3.5) that showed the aperture's shape this heavily...
I'd bet if we experimented with all of our lenses shooting into a leafy
tree or similar background (deliberately left out of focus) using various
apertures, we'd find that each lens produced this iris-
shaped highlight at some point.
Especially when shot wide open, with a distance of some 10 metres between
the in focus foreground, and the out of focus leafy background.
Even my Lentar 135mm f/3.5 preset with its nearly circular aperture will
produce circular-shaped highlights in this shooting situation.
There's more factors than the amount of diaphragm blades and the shape of
the aperture alone. There's a document on my site that explains some of
these factors, it makes for an interesting reading, so if you have some time
for it, it's located here:
http://www.millennics.com/olympus/techdocs/bokeh.pdf
http://www.photoscene.com/lexjenkins/emulaf2.jpg
Funny picture :)
It looks like the emu (SP?) is drunk :)))
This was the best of the lot, with the least distracting bokeh. But white
and green aperture-flare highlights are visible throughout from the bright
sky and reflections off the leaves.- ---
Yes, a typical effect indeed. Still some lenses do this more heavily than
others... This Saturday I can finally pick up what will probably soon be my
favourite lens (guess which one :))) ), and I will perform the bokeh-killer
test on it... Perhaps it will give us some new insights? I'll keep you guys
posted...
Cheers!
Olafo
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