I was reading this text about radiance and according to the next figure, both leaving and arriving radiances' solid angles are anchored on the surface point?
My logic tells me that the solid angle of the radiance arriving at a surface is supposed to be anchored somewhere in the "air" (say at the light bulb position). Something like this:
This way the radiance formula makes sense too, no? (irradiance per solid angle, meaning when the solid angle gets bigger the radiance at point gets smaller)
Can someone shed some light on this?