[Radiance-general] False color and luminance values

[Brian Karr]

Hello all,

 

A question regarding false color and luminance values. Starting with an
image created via rpict, and using the photosphere histogram, the max
luminance value is 351 nits. Selecting a small area around the top outer
corner of the shelf results in a mean around 302 nits. This agrees fairly
close to a measurement with a spot meter on the outer corner of a physical
version of the scene, so far so good.

 

Command: rpict -vtv -vp 0.75 .75 5.5 -vd 0.3 1.0 -0.6 -vu 0 0 1 -vh 45 -vv
45 -vo 3 -va 0 -vs 0 -vl 0 -av .1 .1 .1 -x 2000 -y 2000 -ab 2 -aa .1
shelf.oct > shelf_rpict.hdr

 

File: https://dl.dropboxusercontent.com/u/91366188/shelf_rpict.hdr

 

 

 

With a false color version, the histogram max luminance however is 177 nits,
the small area mean is 131 nits. Im not sure why the luminance values
between the two versions are different?

 

Command: falsecolor -ip shelf_rpict.hdr -e -s auto -n 16 -lh 1000 -lw 225
-log 4 -l > shelf_false_log_norm.hdr

 

File: https://dl.dropboxusercontent.com/u/91366188/shelf_false_log_norm.hdr

 

Thoughts?

 

Thank you!

Brian

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.radiance-online.org/pipermail/radiance-general/attachments/20150104/9aefc263/attachment.html>