• Originally Posted by Bill Burk
So now we have this meter point ten times the speed point for black and white negative film.

But we really consider the normal subject range to be what, 7 1/3 stop?

Where do we expect the normal subject to fall in relation to the metered point? How much above and how much below? Is the meter smack in the middle?
This is about the relationship between the subject luminance range, camera exposure, and sensitometric exposure. I'm working on something that will support my answer to your question. The range above the metered exposure point is approximately 0.92 logs and the range below is 1.28 logs (not including flare).

It works something like in this example. The ranges have been rounded to simplify the example. Note where Hm falls compared to the shadow exposure and remember this is the exposure for a 125 speed film - Hm = 0.0064 lxs Hg = 0.064 lxs.

125 speed exposure points.jpg

For reference, here are the sensitometric exposures for a 0.00 to 3.0 density step tablet exposed at 2.048 lxs.

Sensitometric exposure for 125 speed.jpg