Metering Question For Head And Shoulders Portrait

In line with Rich14's succinct answer, you might find this brief article helpful: A Simpler Approach to Metering.

Just one other "PS".

If you take an incident reading close to the subjects face, be sure that they're aware of what you're doing. That close, you're getting inside their "personal space", and it can cause them to be a bit edgy. Some folks aren't all that comfortable in a studio setting, and the mechanics can be a bit bothersome for them.

Is the light really flat? Light often appears flat but in fact can have some directionality. The film wil see the directionality.

I use an incident meter with a dome, with three readings from the subject position:
- in front of subject pointed directly at the camera
- on highlight side of subject with dome pointing toward the light source however flat it may be
- on shadow side of subject with dome pointing toward the deep shadows, however flat they may be

Exposure is a creative choice, having in hand the data that is needed for rhe decision. If the middle reading is halfway between the others, that is the exposure I use. If not, I have a choice to make.

Sekonic’s website has video and articles on this technique.

All good stuff. The thing to do is pick one and adjust based on your results. I setup all my lights with an incident meter, but than I use a spot flash meter to make sure I'm getting what I want. Note, when I use and incident meter, I meter with the dome pointed at the camera in the brightest illuminated area, and I give one more stop exposure than what it says on the meter. The idea being to place the exposure between the fill level and the Key + Fill level. (The key light shouldn't be brightening the shadowed areas, whereas the key light and fill light illuminate the brightest areas.) For bw, my fill light is usually 2 stops less than my key light.

I've usually incident metered. I can also incident flash meter if using strobes. This has largely been replaced by DSLR tests. A meter works perfectly fine if you are confident and know how to use the meter. But the person being photographed can often benefit with some practice casual photos with a DSLR. You get your lighting right, they get their posing nerves relaxed, minor lighting issues are corrected, communication is improving, everyone's happy with a few good DSLR photos, then everyone's ready for the big camera.

I would want to make 3 readings. The highlight side, the shadow side, and the overall exposure. Portraits look good in the 3-1 and 4-1 range. So I would want to know the ratio in case I had to bump a bit of light in there with a reflector. And then just a straight reading for the exposure, preferably with an incident meter pointed toward the lens, or possibly a gray card at face level with a spot meter.

You meter it just like you would meter anything else you want to photograph. If instead of typing on this thread, the OP would go out and take the photo, develop, print, look at the results and adjust if needed, we wouldn't be having this discussion.