Ben's Comp Newsletter: Issue 039
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Hey,
The first group of 86 students have
just finished up my Python
for Nuke 101 course, and are
getting into creating their own
projects. If you missed out on the
first round, it's not too late to sign
up and level up your
Compositing skillset!
This issue of Ben's Comp Newsletter
includes a couple of neat tutorials
about keying & image
convolution, and sheds some light on
a fascinating Physicist who has
solved an age-old optics
problem.
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STMap Keyer Tutorial
Not
long after I interviewed
him, Erwan
Leroy released
this cool tutorial on how to create
a custom keyer using STMap. Erwan's
tutorial gives a brief but
insightful look into how keyers
work, and how we can create our
own!
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Convolution Matrix Tutorial
Andrea
Geremia has a
neat resource on his website
covering the basics of image
processing. He dives into the theory
behind what the computer is doing,
and also provides some simpler
practical examples of how you can
blur, sharpen, anti-alias or
edge-detect your images in different
ways with a matrix node!
I really appreciate that Andrea
includes "Useful Links" at the top
of this, and every one of his blog
posts or tutorials, so you're able
to further explore the topic should
you want to learn more.
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P.S.
I wrote a simple
article last year about Understanding
the ColorMatrix node,
which is different to the
standard Matrix node. Worth a
read to understand
both!
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W_CatsEye
I
often look towards past show-based
problems when thinking of what to
share in this newsletter, in the
hopes that a learning experience for
me will pay off in a learning
experience for you too! Something
I've had to deal with in the past
couple of shows is strange
non-uniform bokeh shapes in plates
coming from anamorphic lenses.
For the first show, my team got away
with munging up an already-defocused
image and it worked well enough for
what we were doing. The next show,
however, had a lot of bright
defocused lights on dark
backgrounds, causing defined,
distorted bokeh very clearly in the
plates. We had to match this in a
procedural way, which proved to be a
challenge...
This phenomenon of distorted bokeh
with "cats eye" shapes (as shown
in the image above) becomes
obvious when a wide lens' aperture
is wide open. The distortion, or
curved nature of the image, comes
from light entering the lens at
different points across the curved
surface before hitting the camera's
sensor -- this is an extreme example
of lens distortion that we're all
accustomed to in a VFX pipeline.
For the "cats eye" squeezing of the
bokeh shapes, what we're seeing is
essentially the same as what happens
when we create
custom bokeh shapes with
custom-shaped apertures.
More clearly, light enters the lens
through the curved glass, travels
through the aperture blades which
are wide open, and most of that
light makes it to the camera's
sensor. However, a small portion of
that light gets blocked by the
barrel of the lens, therefore
causing the "cats eye" shape vs. a
perfectly spherical/anamorphic oval
bokeh shape.
While pgbokeh is
great for defocusing images with
nice, custom bokeh kernels, it can't
emulate the "cats eye" phenomenon.
Upon testing a few gizmos online,
W_CatsEye by
Wes
Heo seemed
to be the best solution! Out of the
box, it can't take an input zDepth
pass, but cracking open the gizmo
and making some minor adjustments
will allow you to do this.
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Goodbye Aberration
If
you follow the incredible compbanter
instagram account, you may have
already seen a
silly meme about a Physicist
that has solved the problem of
aberration in lens optics.
Sillyness aside, what Rafael
G.
González-Acuña
(and by extention, Héctor
A.
Chaparro-Romo)
have discovered is nothing short of
incredible, and is sure to make
waves in the film industry in the
coming years.
If you're interested, you
can read the paper here, but
it's far from a relaxing bed-time
read...
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Did you find this
newsletter informative?
Have you created, or do
you know of any
outstanding
Gizmos, Python
Scripts or Tutorials
that you would like to
share with the global
Compositing community?
Please send
me an
email, and I
will do my best to
include it in a future
issue of this
newsletter.
If you find value in
Ben's
Comp Newsletter,
please consider
pledging
a small amount
on
Patreon to help
keep this project
running! Contributions
are always appreciated
but not expected.
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