For people with their faces in the shade, you want your hand in the shade, too.
Not necessarily. Firstly, my response was to Minty, who was talking about landscapes, so exposing for people in their own shade is not applicable. Secondly, if you are happy to potentially blow the background then sure, go ahead and expose off your shadowy palm, but there is also the option to expose for the background and use flash or a reflector to fill your subject.
Adjust the meter according to your hand exposure. Then meter the grass & see where the needle falls.
I only mentioned grass for occasions when your palm is not in the same light as the main subject/scene. But you're right, ideally you could/should calibrate the grass to your palm. It can be far quicker and easier to check exposure off grass of known reflectivity rather than your palm, especially if using a long lens, or operating in a retricted space, like a hide, or having to move your palm into light other than that of the subject/scene. In the absence of any such opportunity to calibrate then grass at -2/3 or so rather than your palm at +1 1/3 ought to be a good starting point from which to fine tune.
Using my hand method, skip this step. You've already compensated UNLESS you're using the "Expose to the Right" tut, which is a whole 'nother thing.
It's all in the link I gave you.
I always shoot raw and often do deliberately expose to the right (or at least above a nominally "correct" exposure), especially when shooting a scene with no important highlights, such as my black dog running against a background of 100% grass/foliage.
Example with no edits - shot manual at 1/1250, f/8, 800 ISO, which is 1 1/3 stops brighter than a Sunny 16 exposure. This was shot at +1 stop above a standard "palm" exposure (lighting was about 1/3 stop dimmer than full sunshine), but that was perfect for this scene, with a dark subject that needed detail pulling out, and no highlights to be protected....
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Had I stuck with a "standard palm" exposure the detail on the dog would have been sorely lacking. I know - I've shot many frames of my dog, using a "standard palm" exposure (or grass at -1 stop), and they just do not come out well. In fact, had I used a "standard palm" exposure, the result would have been something like this (exposure set to -1.0 in DPP)....
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Now here is a textbook "Sunny 16" exposure - 1/3200, f/2.8, 100 ISO. The swan is beautifully exposed, just avoiding clipping by a whisker, but look at my poor dog. There is hardly anything to be seen of him. This "correct" exposure for the lighting and the scene as a whole is not great for shooting black dogs.
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In other words, bend the rules as necessary to fit the circumstances....
- Black dog with white swan = standard exposure (protect the highlights).
- Black dog without swan = standard exposure + 1 stop (no important highlights to protect).
From which one can conclude....
- Any scene with important highlights = standard exposure.
- Any scene with no important highlights = standard exposure + a bit (if you like), erring towards ETTR, especially if you shoot raw, but possibly if you shoot JPEG as well.
Backlit subject means you have a choice - expose for the background and add light to the subject, or expose for the subject and to hell with the background, or expose for the background and let the subject look shadowy, or pick a combination.
