[Radiance-general] glare on monitor screen

[Gregory J. Ward]

Hi Yuni,

Discomfort glare and reflected glare off a VDT screen are very  
different, which is why using findglare doesn't tell you anything.   
The contrast lost on a VDT due to reflected glare is a little tricky  
to measure, and there are no corresponding standards.  You can think  
of the contrast as the difference between the foreground and the  
background divided by the adaptation luminance (usually the same the  
background):

	Contrast = (L_fore - L_back)/L_back

Since reflected glare increases foreground and background equally,  
the new contrast becomes:

	Contrast_veil = (L_fore - L_back)/(L_back + L_veil)

The larger the veiling luminance, the lower the contrast.  Does this  
make sense?

-Greg

> From: erika yuniarti <erika_yuniarti at yahoo.com>
> Date: July 25, 2006 11:19:44 AM PDT
>
> Hi Greg,
>
> thank you for your quick reply and your attached LCD info.
>
> Yes correct, I am thinking of veiling glare on the screen that will  
> reduce visibility. Before I received your email, I tried mirror as  
> LCD material. Surely, there is glare (as shown in file.pic), but  
> when I calculate all glare parameter in radiance (dgi, ugr, cie,  
> and others) the results are 0. May be those parameter cannot be  
> used to calculate veiling glare on monitor screen? (high contrast  
> occur vertically on the screen)
>
> Thank you very much, Greg.
>
> Best regards,
>
> Yuni