MadSci Network: Physics
Query:

Subject: Is there a way to convert between light intensity and Luminance?

Date: Mon May 21 09:21:41 2007
Posted by Roman
Grade level: undergrad School: Cooper Union
City: New York City State/Province: NY Country: USA
Area of science: Physics
ID: 1179764501.Ph
Message:

I had an idea of how to map a scene in 3d using a digital camera. I thought to 
use the camera's sensitivity to infrared light and the function of propagation 
of light to determine the distance from an object to the camera in order to 
recreate a 3-dimensional scene. 
A digital camera does not output the intensity of the light at each pixel. At 
best I could find the brightness (I believe it is also called Luminance) of a 
pixel by converting the RGB value to a HSL value for each pixel. 
Luminance ranges from 0-1.0  And the intensity of light could be anything 
positive. So i thought to have a formula like:  lum = 1-1/(Light^n + 1) and 
then light = (1/(1-lum) -1)^(1/n)
So that the function asymptotes at lum=1. To find n I tried using two ledís. I 
took a photo of a wall with 1 on, and then the other, and then with both on at 
the same time. I thought that l light(lum1) + light(lum2) = light
(lum_combined) I understand that the lum would be different depending on 
exposure timing, but, in general, am I going in the right direction?
Thanks, 
Roman R.
   



Re: Is there a way to convert between light intensity and Luminance?

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