How can you have a scene linear reflectance greater than 100%?

Started 3 months ago | Questions thread
Mark Scott Abeln
Mark Scott Abeln Forum Pro • Posts: 18,137
Reflector
1

Mandem wrote:

Good point. Flew over my head for some reason. But how do you translate incident light sources into a reflectance %.

Assuming the reflector is a diffuse, Lambertian surface, like matte paint or unfinished wood, then a reflected metering will have a clear relationship with an incident metering, as the apparent brightness remains the same no matter what angle you view the surface. Otherwise you may have to take lots of measurements and integrate them.

And would this also mean anything above 100% reflectance is by definition an incident light source?

I wouldn’t say “incident” light source, but just a light source: more light is coming off of it than is falling on it.

What’s happening might be subtle. For example, ultraviolet light, which is normally not photographable, can cause materials to fluoresce, sometimes making them brighter than even 100%: in this case, it’s not mainly reflecting visible light, and it’s not necessarily *reflecting* ultraviolet light, but another process is going on. Or, an object in the scene might reflect the light source directly like a mirror, making it brighter than 100% as well. Or an object might be translucent, transmitting light from a hidden light source.

Sorry if I sound like an absolute amateur. I'm still learning.

No problem!

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