[HDRI] RGB values out of range

[Lars O. Grobe]

Hi,

I think there is a misunderstanding here. I am sure that the
documentation you refer to is related to the source images. These are
8-bit coded, and allow values from 0-255. This means that below 20 and
over 200 you get into the edges of this range. As the jpg's you get from
a digital camera are not linear mappings from luminance to pixel values,
and a slight change in these edge pixel values is related to a huge
change in the luminance of the recorded scene, it gets impossible to
reconstruct luminance values from such values. Have a look at the
s-shaped response curve of your camera, it should explain this problem.

So hdr tools can use only this "middle" range, and this means that you
must make sure that the ranges of your overlap have a sufficient
overlap. Also, of course, the darkest (shortest exposure time) image
should not contain any very bright pixels, and the brightest one
(longest exposure time) no very dark ones. So if e.g. your brightest
image was taken with 1/2sec and has significant pixel values below 20,
take one more with 1sec time.

Cheers, Lars.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: smime.p7s
Type: application/x-pkcs7-signature
Size: 3740 bytes
Desc: S/MIME Cryptographic Signature
Url : http://radiance-online.org/pipermail/hdri/attachments/20090909/742bf68a/smime.bin