[Radiance-general] glare on monitor screen

[erika yuniarti]

Hi Greg,
   
  Thank you for your quick reply. 
  I see, so I could not use "findglare". 
   
  is L_fore the luminance of the monitor screen? is L_back the luminance of the surroundings? So you suggest to compare brightness of the monitor screen against brightness of the surrounding?it that so,what contrast level is acceptable?
   
  However, usually, veiling glare on monitor screen causes very bright portions on the screen that the display on the monitor cannot be seen anymore. Isn't it a brightness comparison between areas on the monitor screen it self (instead of brightness comparison between the screen and the surrounding). Or is it not a matter of brightness comparison, instead it is a matter of too much luminance on the screen that we cannot see clear image anymore? If that so, how to get the luminance values occured on the screen (besides the iso contour and false color, because they dont really show value)?

  Many thanks, Greg.
   
  Best regards,
   
  Yuni
   
  
"Gregory J. Ward" <gregoryjward at gmail.com> wrote:
  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 
> 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

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