Responses inline...
> From: "Tyukhova, Yulia" <[email protected]>
> Date: February 20, 2012 12:48:37 PM PST
>
> Everybody,
>
> Thank you for fast responses/tools and suggestions!
>
> Greg,
>
> Thank you for your suggestions and files!
> I am new to Radiance, and I assume that this is what I need to have installed
> on my computer in order to use suggested Perl scripts.
> If you can provide me with the link/info how to run it, that would be really
> helpful!
Actually, you don't need to have Radiance installed. You just need to move the
executables (non-HTML files) from the unpacked directory to /usr/bin or
/usr/local/bin or some other directory in your shell's PATH variable. These
are command-line tools that must be run from the Terminal application under
/Applications/Utilities. I.e., start Terminal and copy the files from your
Downloads folder with:
cd Downloads
tar xzf raw2hdr.tgz
cd raw2hdr
cp raw2hdr dcraw exiftool /usr/bin
cd
raw2hdr
This should give you the usage message I wrote you earlier if it all goes well.
Some basic commands and pointers for Unix are available many places online.
Googling "basic unix tutorial" gave this page at the head of the list:
http://www.ee.surrey.ac.uk/Teaching/Unix/
> Let me restate the question about the compression of the curve in
> Photosphere.
> 1. Do manufactures compress the response curve or maybe it is limited by
> camera/optics/sensor saturation itself on the upper end?
Some camera makers do compress the top end of the response curve, and do funny
things at the bottom as well. Photosphere attempts to discover the tone curve
and correct for these manipulations, but it isn't perfect and if the camera is
changing the tone curve dynamically, it's pretty hopeless. There are settings
you can use on a DSLR to disable such manipulations, but using RAW files
bypasses the problems entirely because the data is linear.
> 2. And I'm still curious, how CF is applied in Photosphere?
A calibration factor is applied equally to all coefficients in the polynomial,
which is exactly the same as applying a linear scale factor after the HDR merge
operation.
> I've been using ND filter t=0.0094 on the luminance meter, because otherwise
> it is impossible to measure such high luminances. I assume, you suggest to
> use it on the camera as well.
Whatever gives you a short exposure that is past the integration time of your
source (1/60th second is acceptable) and not saturated is OK. Specifically,
all values in the short exposure's histogram should be be below 245.
> I'm looking forward to analyze my images with the suggested hdrgen. Luckily,
> I've been taken them in both formats jpeg and raw.
> Greg, will you recommend to have regular calibration scene calibrated at the
> grey card instead of using brighter scene?
The best scene for calibration is a white card in a scene with no bright
sources directed at the camera. The calibration should hold in other scenes
where lens flare is not problematic.
> Thank you,
> Yulia
Certainly,
-Greg_______________________________________________
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