Re: Software correction of out of focus pictures?

Today Dave Martindale commented courteously on the subject at
hand

Today Bart van der Wolf commented courteously on the
subject
That is not correct. With similar techniques as were used
to restore Hubble Space Station's initial imagery, it is
also possible to restore some of the OOF information.

All Things Mopar <nunofyour@xxxxxxxx> writes:
With all due respect to someone I don't know, my first
reaction to your contradiction of my simple statement is,
well, horseshit.

Maybe, but you're wrong. Try searching for
"deconvolution".

What did it cost to fix Hubble, several /billion/ dollars?
And, they did /not/ fix the out-of-focus images /after/
they'd been downloaded to earth, those are toast (yes, they
tried and tried and tried, but never succeeded to any
measurable degree).

They did succeed in sharpening many images in the several
years before the Hubble optics were fixed. The Hubble was
unable to shoot images of dim stars, one thing it was
originally designed for, because the light was spread over
so many pixels. But bright objects could be imaged and the
defocus largely corrected, because they knew the
telescope's blur function so well.

Again, I say "horseshit". If they succeeded so well, why did
NASA spend /years/ and countless /millions/ of dollars and
mount a very specialized shuttle mission to correct the
Hubble's underlying problem if they could simply correct it's
blurry images using a technique as simple as deconvolution?

You theoretical elitists have to understand an indisputable
fact: pixels cannot be created where there are none. When
looking closely at the pixel map of a sharp, detailed, in-
focus image vs. a blurry, obviously out-of-focus image, the
pixels defining the fine detail are simply not there and no
amount of hand waving and black magic can bring them back. All
that can be done is various mathematically valid ways to trick
the human eye into /thinking/ the image is sharper.

And yes it cost a lot to fix Hubble, but that was a
hardware fix. One camera module was replaced by a very
complicated mirror assembly that corrected the error in the
primary mirror. That doesn't mean the software sharpening
of the blurred images cost this much.

NASA engineers and astronomers colaborated to add software
to Hubble and some electronics (as I recall, but I'm no
Hubble expert) to compensate - not correct - the incorrect
mirror curvature grind to allow /new/ images to be
in-focus, and then through some pretty sophisticated -
read: extremely expensive mathematical techniques.

You're just making this up, aren't you?

No, the correction device was hardware only. Once
installed, the telescope delivered sharp images to the
various sensors without any postprocessing needed. As I
understand it, the added optics were arranged to image the
primary mirror onto a special correction mirror. Because of
this, all the light that reflected from a particular point
on the primary mirror was re-gathered at a single point on
the correction mirror. That allowed the error in the
primary mirror to be corrected by a complementary
correction in the new mirror. All the light from a single
star was focused on a tiny spot a few pixels in size, as
designed.

And, the space inside Hubble the
astronaut had to work in was so tight and the chance to
irreparably damage the telescope was so high that nobody
really knew in advance if Hubble could or could not be
fixed.

Really, what's this got to do with software sharpening?

The result will not be perfect, because the truely lost
information will generate artifacts during the
restoration process. It is also important to have a good
model for the de-focus. Some so-called "blind"
deconvolution algorithms estimate the blur function,
other methods require prior input of the model to be
used.

What kind of techno babble is this?

It makes perfect sense if you'd bother to do any kind of
search for deconvolution methods.

I know what deconvolution is but my statement stands: how can
a person blowing their vacation pictures predict just how it
was done so they can give the correct model to the software?
Further, how much does it cost, how is it used, how long per
image does it take to optimize results, and what nasty side-
effects are created?

I'm
supposed to know in advance exactly how I blew it, so the
software knows how to begin? If I'm misunderstanding you, I
apologize but I fail to see how someone can predict the
way(s) to blow a focus.

It could be as simple as having a bright point source in
the image (the reflection of the sun off a small metal
ball, for example) which allows estimating exactly what the
blur function looks like. If you know what the blur did to
the image, you can invert it (with the caveats that Bart
mentioned).

I seriously doubt that a few spots of glare across an
otherwise bland expanse of pixels typical of a blurry image
are enough for even sophisticated software to latch onto and
figure out how to reconstruct hundreds of thousands - or
millions - of missing pixels.

As you point out, all this may not be worthwhile in most
cases in general photography. But you as much as called
Bart a liar, while at the same time mangling much of what
you said about Hubble.

I never used the word "liar" but if you want to interpret my
comments that way, that's your privelige. I also said I'm no
Hubble expert, so I'd hardly call what I said "mangling" it.
And, your 1st statement, where you agree with my thesis, says
it all: these techniques are /not/ for the general case, so
have no general use whatsoever to real-world photographers
trying to save their European vacation pictures or pictures of
their daughters wedding.

You elitists need to get out of the basements where the
computer wonks live and come up and smell the fresh air where
normal people live and discuss /in practical terms/ how to use
these esoteric techniques in a reasonable inexensive, time-
efficient, least side-effect way on /real/ photo image
situations across a large spectrum of subjects and lighting
conditions. Until/unless you can do that, when I smell
unadulterated crap, I'll yell "horseshit".

Bye!

--
ATM, aka Jerry

"Whether You Think You CAN Or CAN'T, You're Right." ? Henry
Ford
.

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