[Radiance-general] Pvalue for converting to luminance

[chang cw]

Hi Greg,
Thanks for replying so fast.
So i assume that the value read off from ximage is the same at that
from pvalue ?

Using -b -o option  and a factor of 179 ?
Sorry but i could get not the radiance source compiled for ximage ;(

Thanks
Chew Wai

On Sat, Sep 6, 2008 at 10:36 AM, Greg Ward <gregoryjward at gmail.com> wrote:
> Hi Cw,
>
> I'm not sure how pfsview converts colors to luminance values, but it may
> apply a different set of coefficients from those used in Radiance (and
> pvalue).  This could explain the discrepancy.  The best way to check is to
> compare values for a gray pixel, which should be the same regardless of the
> color -> luminance conversion.
>
> Also, are you 100% sure you are checking the exact same pixel(s)?
>
> -Greg
>
>> From: "chang cw" <solomoncw76 at gmail.com>
>> Date: September 5, 2008 7:27:46 PM PDT
>>
>> Hi all,
>>
>> I tried to apply the factor of 179 to the scaled brightness from
>> pvalue. However, it seems that the value is still slightly off from
>> the actual one read from psfview.
>>
>> The value from pfsview is 2.579e+4
>>
>> while from pvalue is 2.803e+4
>>
>> i used pvalue -b -o sample.hdr
>>
>> Is there an exact value for the scale ?
>>
>>
>> Thanks
>> Cw
>
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