I have been reading and watching re: metering with slide film which has a 2 stops over and under ability to capture the information. Then some people use the average function on their light meter after metering the highlight and the shadows.
What happens if the scene has 1 stop under midtone and 3 stop over? Does the slide look underexposed but the details are still captured?
Thanks.
2 EV above middle-grey is where you still get all the texture. Above that the shoulder begins and the texture begins being lost, slowly, gradually.
So one should know what the situation really is.
Let's say a model with a white jumper and a darkish hat, and 4 EV in difference of reflectivity between jumper and hat (model skin somewhere in between).
The jumper will be rendered white and textured also if placed, let's say, at 2.3 EV above middle grey (you measure the jumper, and you open 2.3 EV more than what the lightmeter tells you).
The hat will fall 1.7 EV below middle grey (because it was 4 EV below the jumper, in your hypothesis) which is still full of details. It might appear a bit darker than what you "saw" it but unless the hat is a "reference" dark grey well known and which must recogniseable in the picture (let's say a trademark that you want to render with an exact tone) you don't care much.
Or you could place the white jumper at +2 above middle grey and the hat will fall 2 below middle grey, in this case you sacrifice the tone of the hat (you place it a bit darker) but you are sure you get all the texture of the jumper.
If this is a catalogue picture of the white jumper, +2 EV above middle grey will preserve all the details and would maybe be preferable. If the girl is the subject, you sacrifice some little detail in the texture of the jumper, you can expose the white jumper for +2.5 or so, you don't care about preserving all the texture in the jumper. Actually if the girl is the subject I would use an incident-light meter in front of the girl, a spot-reflected light meter on the jumper, and worry of the jumper only if it is let's say 4 EV above middle grey (some parts of the face in the shade, some part of the jumpes in full light). Else I wouldn't worry at all, in uniform light the jumper will be rendered with good details in any case, due to the shoulder behaviour of the film.