[Radiance-general] rtrace for luminance values

[Mehlika Inanici]

Hello John. You can use the getinfo command to look at the exposure of 
an Radiance image. The exposure value is given as EXPOSURE=.... If there 
is no exposure line, exposure is 1.00 by default.
Hope it helps...
Mehlika

John An wrote:

> I have run into a problem that I think Mehlika Nur Inanici had a 
> couple of year's back.
>
> I am trying to use rtrace to get luminance values on top of a desk 
> surface.  The command I'm using is:
>
> cnt 6 12 1 | rcalc -e '$1=51+((72/6)*$1+6);$2=96+((144/12)*$2+6);$3=30' \
> -e '$4=0;$5=0;$6=1' | rtrace -h -ov @../options_aa08_ab5 -af 
> b_b_m_2_bare_aa08_ad1024_ab5.amb -e 
> b_b_m_2_bare_illumgrid_task_08_l.out b_b_m.oct \
> | rcalc -e '$1=179*(.265*$1+.670*$2+.065*$3)' > 
> b_b_m_2_bare_illumgrid_task_08_l.dat
>
> The values reported by rtrace are in the range of 0.1 to 0.2 
> candela/meter squared.  However, in an image, I am getting values in 
> the range of 1.5 to 2.5 candela/meter squared (which is much more 
> reasonable).
>
> In response to Mehlika's question, Schorsch had mentioned that the 
> header to the pic file would give an exposure value, and that 
> luminance = 179*(.265*R+.670*G+.065*B) / e.  But I can't seem to find 
> the exposure.
>
> What am I missing?  Where am I not looking?
>
> Thanks.
>
>
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