Bokeh and Aperture Shape

Just watched Die Hard 4 and I noticed that the Bokeh in the close-up shots
looked a bit unattractive, particularly with light sources in the
background. Look like 8 blade apertures, but not smooth edges. Very
distinctive shape.

Just curious, is there a reason for the difference between high-end video
lenses and high-end still lenses with regards to aperture?

On Jul 8, 3:37 pm, "Ali" wrote:
Just watched Die Hard 4 and I noticed that the Bokeh in the close-up shots
looked a bit unattractive, particularly with light sources in the
background. Look like 8 blade apertures, but not smooth edges. Very
distinctive shape.

Just curious, is there a reason for the difference between high-end video
lenses and high-end still lenses with regards to aperture?

I had a friend and associate, a super lens designer, who did quite a
study on this. He wrote a paper that was, as far as I know,
unpublished. He did, however, do a shortened and simplified version
for the "gleanings" column of Sky and Telescope. This would be back
in late 70s or early 80s. He did quite a few cases with very odd
shaped apertures and some with multiple, close spaced apertures. His
name is David Stolzman. I believe I have a copy of his longer paper
somewhere in my files, but it will take me awhile to find it.

This study was so interesting I have been long tempted to make a
pinhole camera with replaceable apertures and make a series of photo-
etched apertures. One idea he played with was a graded edge aperture
that could also be photo reproduced. This is sometimes called an
apodized aperture.

Thank you for your post, however surely camera equipment on a blockbuster
movie for these types of shots should have nice bokeh?


"RockyZ" wrote in message
...
On Sun, 8 Jul 2007 21:37:38 +0100, "Ali" wrote:

It all depends on how the lens designer wants to
arrange things by balancing cost, efficiency, and image quality as well as
the
type of glasses selected for that particular lens design. (A lens'
resulting
bokeh is not usually a high-priority with lens designers. Chromatic
aberrations,
field flatness, and angular distortions are of much greater importance.)

Ali wrote:
Just watched Die Hard 4 and I noticed that the Bokeh in the close-up
shots looked a bit unattractive, particularly with light sources in the
background. Look like 8 blade apertures, but not smooth edges. Very
distinctive shape.

Just curious, is there a reason for the difference between high-end
video lenses and high-end still lenses with regards to aperture?



It is entirely possible that the lens was chosen specifically for this
feature. The Director of Photography for this sort of production would
have all manner of lenses at their disposal. These guys are masters of
their craft and are able to select tools to produce the result they want.

Absolutely, I agree. That's why I am curious why they used a lens with this
bokeh. There must be a reason for it.


"Zen Diver" wrote in message
...

It is entirely possible that the lens was chosen specifically for this
feature. The Director of Photography for this sort of production would
have all manner of lenses at their disposal. These guys are masters of
their craft and are able to select tools to produce the result they want.

On Tue, 10 Jul 2007 18:48:52 +0100, "Ali" wrote:

Absolutely, I agree. That's why I am curious why they used a lens with this
bokeh. There must be a reason for it.

The choice of a lens has to do with the look of that lens. A lens can be
tacksharp, or nice and soft. Has flares which the DP can like, low or high
contrast, etc etc.

cheers

-martin-
--
Official website "Jonah's Quid" http://www.jonahsquids.co.uk

On Jul 10, 3:14 pm, Martin Heffels wrote:
On Tue, 10 Jul 2007 18:48:52 +0100, "Ali" wrote:
Absolutely, I agree. That's why I am curious why they used a lens with this
bokeh. There must be a reason for it.

The choice of a lens has to do with the look of that lens. A lens can be
tacksharp, or nice and soft. Has flares which the DP can like, low or high
contrast, etc etc.

cheers

-martin-
--
Official website "Jonah's Quid"http://www.jonahsquids.co.uk

Different spot profiles create different looks. For instance, a
diffraction blur has a completely different look than an out of focus
blur, which is different than the blur from many aberrations. In
fact, almost all lens aberrations give a unique look. Not all blur is
the same.