[Radiance-general] Re: Comparison of values measured by sensors and calculated with Radiance (Greg Ward)

[Greg Ward]

Dear Sung,

It seems I misread your diagram the first time, so misinterpreted  
your problem.  I'm thinking now that the issue may be the cosine  
correction of your sensors rather than what is going on in Radiance.   
Most lux sensors have a crude calibration with respect to incident  
angle.  I recommend checking your sensors against one that is more  
reliable, or at least verifying that they have the proper cosine  
response by measuring a point source at varying incident angles.

Best,
-Greg

> From: Minki Sung <mkii at iis.u-tokyo.ac.jp>
> Date: April 2, 2009 12:42:28 AM PDT
>
> Dear Greg,
>
> Thank you for your advice and I just tried as you said but actually  
> the results were not improved as following link.
>
> http://iga.iis.u-tokyo.ac.jp/xe/?document_srl=346
>
> That might be so because the lamp is actually UV lamp but as you  
> know, there is almost no difference between flourescent and UV  
> lamps besides with or without phosphor coating on the surface of  
> lamp. Nevertheless, I thought the absence of phosphor coating could  
> cause some differences on the diffuse of UV including the Fresnel  
> effects. I'm finding some references on the diffuse of UV lamps.
> The reflectances were referred to a japanese paper which had done  
> experiements with UV and the UV output of lamp was referred to the  
> manufacturer's specification but the UV intensities at 1 m distance  
> is almost the same.
>
> Additionally, I'm checking the UV sensor but as it also follows  
> cosine law as illuminance sensors do, there might be no problem  
> with UV sensor.
>
> Sung