We agree here again:
hungryjoe wrote:My camera's metering circuitry measures the light reflected by my subject. In a comparison, the subject would have to be constant, which was why I mentioned zooming in on your subject as you move back - to keep the subject filling the frame. Even if you move back a considerable distance and use a spot meter, if your subject is constant, for argument, say 18% reflectance, you are going to get the same reading.
That's because, as I've finally realised, when you half-press your shutter button to get a meter reading your physical aperture size will be larger when you've stood back and extended the focal length of the lens
. And yes, your camera's metering circuitry measures light reflected by your subject, all I'm saying is that as far as your camera's concerned there
is no other light source since all it can see is your subject, no flash, no sun, no etc. To your camera, the subject
is the source of light, and it measures the light emanating from it (replace with whatever term you like - coming, reflecting, etc, it makes no difference). And I know that you use a hand-held meter as close to your subject as possible, I wasn't suggesting otherwise in a practical situation.
And for the third time:
hungryjoe wrote:First, it's highly unlikely that the light reflected by your subject, qualifies your subject as a point source of light, so the Law Of Inverse Square doesn't come in to it.
I've already accepted that over studio distances it doesn't apply! 50 feet man, 50 feet I said!