Re: [Openexr-devel] Query: Image Based Lighting and HDRI-enabled cameras

[Brian Willoughby]

[  There are 12-bit per component HD cameras. Take a look at Thomson
[  Filmstream Viper[1] using RGB 4:4:4 10-bit log (the A/D converter
[  are 12 bit linear).
[
[   [1] http://www.thomsongrassvalley.com/products/cameras/viper
[
[  The DALSA Digital Cinematography[2] camera record 14-bit in 4x2k
[  resolution.
[
[   [2] http://www.dalsa.com
[
[  I'm myself involved in a project building something of a
[  "mini-DALSA" recording images in 2k resolution and RGB 4:4:4
[  directly over FireWire.

Thanks for the links.  I have been looking for such capture technology.  (Now  
I need to look for funding, or at least someone in the Seattle area with such  
equipment who is willing to offer occasional access to an experienced  
programmer with HDRI interests).


[  Remember that 10-bit is integer while 16-bit half is float values.
[  When someone speak about 10-bit one will always assume that the
[  image data is in log space.

I did not realize that "10-bit" has such a strong assumption of log in the  
film industry, but it makes sense, given the standard set by Cineon.  Thanks  
for pointing that out.  Fortunately, more of the literature I am reading these  
days mentions "log" clearly.


[  Logarithmic encoding is an efficient compression of color based
[  upon the principle that the human eye is more sensitive to low-
[  and mid-tones than to highlights. These highlights can be
[  compressed and stored using fewer bits than the linear original.

I understand the motivation for 10-bit in these cameras (RGB fits into 32-bit  
words), but I do not agree with the limitation that the original 12-bit values  
cannot be obtained outside the camera.  I realize that the losses are  
perceptually minimal in the translation, but there are losses.

Brian Willoughby
Sound Consulting