[rollei_list] Re: Aperture shape... bokey again and iris shape
- From: bigler@xxxxxxxx
- To: rollei_list@xxxxxxxxxxxxx
- Date: Fri, 12 Jan 2007 11:13:05 +0100 (CET)
From Petr :
>...In my experience, the shape of the opening directly influences how
>the out-of-focus spot highlights are rendered in the picture. The
>spot highlights have similar shape as the aperture.
To illustrate this, I have placed some test images here
http://www.flickr.com/photos/43175600@N00/sets/72157594474834671/
The images are recorded with a digital SLR and what we can say is that
when defocusing is huge, the classical model works perfectly with a
silicon sensor !
Abour bokeh and digital, I am suspecting that digital processing of
the sampled image somewhat changes the rendering of out of focus parts
of the image. Many consumer (and even some professional-grade) digital
cameras have some kind of anti-aliasing filter, and I am suspecting
that some heavy digital processing is made to increase the edge
sharpness before delivering the final digital file accessible to the
photographer. So the gradual loss of sharpness due to a combination of
residual aberrations and the projection of the iris shape can be
heavily modified by the applied digital process.
But for gross defocusing, no mystery ! the classical ray tracing
applies !
My undesrtanding is that the digital processor has no means to know
what is purposedly blurred out of focus and what is unsharp due to the
anti-aliasing low pass filter !!!
Fortunately, reasonable people who continue to use film cameras do not
have to care for this ;-);-) they can enjoy the pure bokeh,
organically grown (and certified as organic by an independant
institution) of their favourite organic lens + film combination !
--
Emmanuel BIGLER
<bigler@xxxxxxxx>
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