Practical application of metering basics
Help me out here please. What I think I know in theory doesn't seem to work in real life. I would like to use two scenarios, one with wildlife and one with landscape photography, and you tell me where I'm wrong. Both scenarios have to do with spot metering, how the camera renders the image in middle gray, and the appropriate correction required by the photographer. Both cases assume manual exposure control, and spot metering.
Landscape scenario: a given composition includes a waterfall, the associated cliff face, trees, and blue sky. If I wanted to apply the zone system to capture the image, I would spot meter on the white of the waterfall. With no correction from me, the camera would underexpose, rendering the waterfall middle gray, about a zone 5. But if I want the waterfall to be a zone 8, I would open up 3 stops, from the initial exposure that the spot metering read. This would result in the highlights of the waterfall being properly exposed and preserved. Is this correct?
Wildlife Scenario: Just say I'm photographing a Raven, or anything that's darker than middle gray. If I spot meter on the subject, the resulting reading will overexpose. I will have to stop down to some degree to get a properly exposed image. Is this correct?
The overall concept I have is that if something is brighter than middle gray and spot metered, the camera will underexpose, because it's trying to make the scene middle gray. And the reverse for subjects darker than middle gray. My examples above just restate this in more words, but the practical application may be where I'm off.
If my understanding is correct, then my metering is the problem. If not, please tell me where I went wrong. :)