As far as I understand it, a light bulb irradiance (and illuminance) fall off following the inverse square law with distance, however radiance does not.
I wondered why we (and cameras) do not see objects as dimmer as we get farther away from them. Searching around I’ve found two possible explanations:
The object’s light (irradiance) does get dimmer, but with perspective the object appears smaller so the two effects cancel out, and the perceived brightness is the same.
The eyes/camera measure radiance which does not change with distance.
Radiance seems to have nothing to do with perspective so they kind of contradict. If the latter is correct, then why use lenses to “convey” more rays in one point as radiance remains the same? (Only irradiance inside the eye/ image film is higher.)