Re: Betterlight Camera Calibration
Re: Betterlight Camera Calibration
- Subject: Re: Betterlight Camera Calibration
- From: Karsten Krüger <email@hidden>
- Date: Sat, 4 Oct 2008 15:10:33 +0200
Am 03.10.2008 um 00:34 schrieb Stanley Smith:
My thoughts exactly, but you still have to attach an HP printer to
make this system work.
Yes, but just as a dongle. It is not involved into processing the
images. HP just makes shure they get something :-)
The more I think about this I am wondering if there is not some
"secret sauce" in HP's profile creation procedures. If they truly
are adding the spectral readings from the painting surface into the
mix of patches used to calculate the "scene referred" camera
profile, then they would have to know precisely where these
measurements were taken (down to the pixel), in order to compare the
spectral measurements to the corresponding area of the captured image.
The way Robin explained it to me is that it is not necessary to know
the exact location of those colors. He used an analogy to signal
processing - you can create a square wave by using specially crafted
sine waves. The same thing but reversed is done with Fourier-
transformations happening in the background of JPEG compression methods.
When looking at a painting you will hardly ever find an area with
solid colors like on a Color Checker. Propably two or three original
colors are allways mixed together at a certain location on a painting.
So a clear reading of a single color is nearly impossible. And a
standard approach to optimize a profile, like it is possible with a
Color Checker, does not work.
I believe they are analysing the spectral response of the colors used
to create the painting, detect patterns of similar responses and thus
kind of understand which original colors have been used.
I hope Robin can come up with some background info on this.
Karsten
P.S.: Just found a nice place while googling on this topic: http://www.handprint.com/LS/CVS/color.html
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