I made the above illustration one afternoon for my class -- using a reflected light meter built into a camera. There are three photos there; The top scene shows two sedans parked across the street from my house. Below the silver sedan is a section of the door panel directly below the door handle. Below the charcoal sedan is a section of the door panel directly below the door handle.
First I took the photo of the entire scene including both cars using the camera meter's exposure determination. One car reflects more light than the other. With both cars in the scene the meter averages the reflectance of both. Then I walked across the street and got real close and photographed the silver car door panel -- then the charcoal car door panel. In these two photos I again used the camera meter's exposure determination.
ALL THREE EXPOSURES WERE DIFFERENT. The exposure for the silver car door panel was less than the overall scene and the exposure for the charcoal door panel was more than the overall scene. The camera meter darkened the silver car's door panel and lightened the charcoal car's door panel.
Open the photo in an app like PS or GIMP where you can measure HSB (hue, saturation, brightness) values and check those four spots. In the top photo I get a brightness value for the silver car door: 53 and for the charcoal car door: 16 -- the point: that's a substantial difference as it should be -- the silver car reflects more light and is brighter. In the two closeups of the door panels I get silver car door: 38 and charcoal car door: 39.
Joe
Hmm. So if I'm not mistaken, this is similar to the instance of shooting in bright snow where the camera's meter attempts to move the white snow to middle grey and so you have to compensate the exposure.
Thanks everyone for their replies, but I have to admit I'm still a little muddled.
The main point of contention is... for example:
I have this EV chart that says EV15 is for a clear sunny day (Sunny 16), but that EV16 is also a clear sunny day, except with bright snow or sand.
This leads me to believe that the reflected light coming off the snow or sand affects the exposure in that one must adjust to the added light (from the "reflectance") by stopping down.
Then, if I extrapolate this information, almost any scene where there are objects that reflect a lot of light (white surfaces for example), I must not only take into consideration the current weather and light, but also the reflecting light coming off the objects (incident light and reflectance vs. just incident light).
So, going back to the snow-middle grey compensation, or the silver and charcoal cars. Is the meter's darkening of the silver car and brightening of the charcoal car due to a factor of color and tone? As in it's trying to get it to middle grey? (not to mention the snow). That makes it seem like it doesn't have to do with light, but with... colors.