Comparison of values measured by sensors and calculated with Radiance (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

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From: Minki Sung <[email protected]>
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

No problem. It was really my fault for not looking at your nicely prepared diagram more closely -- I somehow missed the numerical table. You explained your problem very well.

-Greg

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From: Minki Sung <[email protected]>
Date: April 2, 2009 7:37:33 PM PDT

Dear Greg,

I am so sorry not to have explained the model enough. I'll check my sensors at first and drop a line here if I could find what is problem. Thank you again for your kind reply.

Best Regards,

Sung