Dear all,
I want to visualize 3D designs of TV-Sets and display them on calibrated broadcast class A monitors with EBU phosphors.
Is it possible to tell Radiance not to work with the WHTEFFICACY of 179 lm/w but the MAXEFFICACY factor of 683 lm/w?
Furthermore i want to use RGB color space with the 'nominal CRT Primaries' which are the same as the EBU phosphor coordinates in 'color.h'.
I saw the data in the header file but i dont know how to change it. I guess this change will affect other programs like falsecolor to.
Whats the advantage working with 179lm/w anyway? In every book i see the factor of 683 lm/w!
···
-----
#ifdef NTSC
#define CIE_x_r 0.670 /* standard NTSC primaries */
....
#else
#define CIE_x_r 0.640 /* nominal CRT primaries = EBU color space*/
#define CIE_y_r 0.330
#define CIE_x_g 0.290
#define CIE_y_g 0.600
#define CIE_x_b 0.150
#define CIE_y_b 0.060
#define CIE_x_w 0.3333 /* use true white */
#define CIE_y_w 0.3333
#endif
-----
Does Radiance use the NTSC color space by default ?
I want to create an octree containing the data of a tungsten light source i measured.
My goal is to measure the right illuminance under the lamp. I achieved it with this command:
echo "1 0 0 0 0 1" |rtrace -I -h lux_test.oct \
> rcalc -e '$1=179*(0.26510582*$1+0.67010582*$2+0.0647883598*$3)'
But i want to create an octree where i can use this command:
echo "1 0 0 0 0 1" |rtrace -I -h lux_test.oct \
> rcalc -e '$1=683*(0.299*$1+0.587*$2+0.114*$3)'
These factors are the EBU equivalents for brightness in the Y channel.
I hope i made myself understandable, its critical that i can measure the correct colors and the correct brightness in Radiance to make sure the display will show the exact colors of the design!
Thanks for help so far,
Christian
--
Christian Fusenig
Diplomand, Medientechnik
Undergraduate, Media Technology
Hamburg University Of Applied Sciences
http://www.mt.haw-hamburg.de
address: Beim Schlump 27/07
20144 Hamburg
email: [email protected]
mobile: ++49 179 5975845
Hi Christian,
Sorry for the slow reply. I was hoping someone else would field this, then I forgot about it.
Radiance does not use the NTSC color space. By default, it uses the primaries you found after the NTSC ones in color.h. There is a history to the WHTEFFICACY value, which is explained (more or less) in the old Radiance Digests. See:
http://radsite.lbl.gov/radiance/digests_html/v2n0.html#LUMFACTOR
The bottom line is that the peak efficacy of 683 lumens/watt is only the right value at 555 nm, and a poor approximation to the efficacy over the visible spectrum. In the end it doesn't matter what factor you use, as you divide by it going from photometric units to radiance and multiply again coming out. In other words, the factor goes away.
If you want to change the notion of what RGB colors Radiance uses, there is no formal way to do this. You just do it. You specify your sources and materials in your desired RGB space, and Radiance doesn't really care what color space it's working in. To work properly with various programs that properly interpret Radiance RGBE images, you should probably add a line of the form:
PRIMARIES= .603 .352 .289 .590 .146 .066 .319 .348
where these numbers correspond to xr yr xg yg xb yb xw yw, respectively. To add a line to a Radiance image, you can use the vinfo script.
I hope this is helpful.
-Greg
···
From: Christian Fusenig <[email protected]>
Date: February 11, 2006 11:37:58 AM PST
Dear all,
I want to visualize 3D designs of TV-Sets and display them on calibrated broadcast class A monitors with EBU phosphors.
Is it possible to tell Radiance not to work with the WHTEFFICACY of 179 lm/w but the MAXEFFICACY factor of 683 lm/w?
Furthermore i want to use RGB color space with the 'nominal CRT Primaries' which are the same as the EBU phosphor coordinates in 'color.h'.
I saw the data in the header file but i dont know how to change it. I guess this change will affect other programs like falsecolor to.
Whats the advantage working with 179lm/w anyway? In every book i see the factor of 683 lm/w!
-----
#ifdef NTSC
#define CIE_x_r 0.670 /* standard NTSC primaries */
....
#else
#define CIE_x_r 0.640 /* nominal CRT primaries = EBU color space*/
#define CIE_y_r 0.330
#define CIE_x_g 0.290
#define CIE_y_g 0.600
#define CIE_x_b 0.150
#define CIE_y_b 0.060
#define CIE_x_w 0.3333 /* use true white */
#define CIE_y_w 0.3333
#endif
-----
Does Radiance use the NTSC color space by default ?
I want to create an octree containing the data of a tungsten light source i measured.
My goal is to measure the right illuminance under the lamp. I achieved it with this command:
echo "1 0 0 0 0 1" |rtrace -I -h lux_test.oct \
> rcalc -e '$1=179*(0.26510582*$1+0.67010582*$2+0.0647883598*$3)'
But i want to create an octree where i can use this command:
echo "1 0 0 0 0 1" |rtrace -I -h lux_test.oct \
> rcalc -e '$1=683*(0.299*$1+0.587*$2+0.114*$3)'
These factors are the EBU equivalents for brightness in the Y channel.
I hope i made myself understandable, its critical that i can measure the correct colors and the correct brightness in Radiance to make sure the display will show the exact colors of the design!
Thanks for help so far,
Christian