[Radiance-general] Re: diffuse + specular > total reflectance?

[Lars O. Grobe]

Hi,

thank you for the reply! The material is an aluminium surface finish
with coatings. I do not know about the roughness yet, as it was not
provided. I know that the total reflectance was determined using an
integrating sphere, and at an angle of 30 degree (whatever this really
means in detail - where is the angle in this measurement?), the specular
reflectance was measured according to ISO 7668.

As far as I understand, the routine is to point a light source at the
sample point under the indicated angle (which is given as the angle
between surface normal and the line between the sample point and the
light source. On the opposite side, the sensor is pointed at the same
sample point. 60 degrees is a standard for aluminium measurements
according to the ISO 7668.

As the surface roughness influences the measurements, the term used here
is gloss (a nice explanation is found at wikipedia
http://en.wikipedia.org/wiki/Gloss_(material_appearance) ). If someone
can share a nice definition of the difference between gloss and specular
reflectance it would be highly appreciated ;-)

And I have to read a bit before I can follow you about how to determine
the roughness.

CU Lars.