- #1
henksp
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I need formula's to calculate the luminance from a sphere.
When a flat Lambertian surface is illuminated then:
luminance [cd/m2] = illuminance [lux] / pi (3.1415..).
The light falling on the surface radiates back into 2 * pi, and integrating the cosine of the lambertian surface results in pi. So the end result is pi / (2 * pi) = 1/pi.
But now I put an isotropic light source of 1 candela inside a homogeneous translucent sphere. What is then the luminance at the outside of the sphere (assuming 100% transmission of the translucent material)?
Now a infinite piece of surface on the sphere radiates into more than 2 *pi depending on the curvature of the sphere. But how to calculate this?
Secondly: does the cosine law for the Lambertian surface apply also for a curved surface? I think it's also dependent of the curvature.
Can someone help me out ?
Many thanks,
Henk
When a flat Lambertian surface is illuminated then:
luminance [cd/m2] = illuminance [lux] / pi (3.1415..).
The light falling on the surface radiates back into 2 * pi, and integrating the cosine of the lambertian surface results in pi. So the end result is pi / (2 * pi) = 1/pi.
But now I put an isotropic light source of 1 candela inside a homogeneous translucent sphere. What is then the luminance at the outside of the sphere (assuming 100% transmission of the translucent material)?
Now a infinite piece of surface on the sphere radiates into more than 2 *pi depending on the curvature of the sphere. But how to calculate this?
Secondly: does the cosine law for the Lambertian surface apply also for a curved surface? I think it's also dependent of the curvature.
Can someone help me out ?
Many thanks,
Henk