Lecture 11: Radiometry and Photometry (38)
leoadberg

Wow, it's kind of amazing that the human eye can see stuff that's 1000x dimmer than a moonlit scene.

andrewdotwang

What's the difference between luminance and illuminance? Could we use illuminance to describe the brightness of a computer screen?

gabby-delforge

@andrewdotwang, I think of it this way:

Illuminance is the light received by a surface. This is why there is a sharp falloff, and why the illuminance we get from starlight is only 0.0003 even though stars are very bright - very little of that light actually reaches us.

In contrast, luminance is associated with a ray of light - either emitted from a surface, bouncing off of that surface, or passing through it.

In your example, you would use luminance to describe the brightness of a computer screen, and illuminance to describe how much light from the computer screen (and your surroundings) falls onto your face.

borongzhang

thank you, gabby!

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