'...a specular reflection is of the same intensity as the source...'
Um, Jay, I hope that you don't mind me offering a different interpretation:
Most materials reflect some of the light striking them in a specular manner and some in a diffuse manner. Few materials are totally specular or totally diffuse (there's a name for totally diffuse like 'La...ian' - Laplace, Lagrange, Lambert? - I forget: I'll have to look it up). Further: the specular part of the reflection often occurs in a lobe (ie a 'single ray' of incident light is reflected into a narrow cone of specular reflection. So when you see the reflection of the sun on most surfaces you can see it over a small range of angles, and thus it is visible as a bright spot that is larger than the one you would see from a mirror.
All that means that there is no need for the specular reflection to have anything like the same intensity as the source.
It's a lot easier to explain with a little intensity vs angle polar diagram, so I'll draw one and scan one in if you like.
'so an incident reading in direct sunlight should be the same as a spot reading of a specular reflection'
Oops, that doesn't follow. An incident reading in full sun is, and should be, very different from a spot reading of the sun*! The fact that a spot reading of the specular reflection is nowhere near a spot reading of the sun (unless you are reading the reflection of the sun off a mirror) is just an example of the specular reflection not being the same intensity as the source.
*not that one would ever contemplate doing such a thing.
Last edited by Helen B; 01-17-2005 at 12:11 PM. Click to view previous post history.