Ansel Adams, American landscape photographer, invented selecting exposure value way, called "Zone system". It consider the tone to divide 10 steps between black and white (it is called "Zone") on image.
If you consider the system, the luminance scale as the width (step) of Zone, you can image reproduction on a print when take a photo.
Each Zones are determined as following;
This grayscale isn't equivalent with the real density, but please put it on your exposure meters, and use it for a help of imaging.
Practice of Tone Reproduction
Now I introduce a method that take a real scene, and to demand ISO equivalency speed and developing time by the difference between the part of highest light and the part of deepest shadow in the scene.
Tools and materials
1. Select the area that luminance scale is between 7 steps and 9 steps, and frame a camera as fitting in those area
2. Set sensitivity of a spotmeter to the ISO sensitivity that is printed in the film package.
3. Select a deepest point which needs slightly details in the object (yellow point in the right photo), after measure that and write down the measurements. (1)
4. Next, select a highest point which needs slightly details in the object (in right pic.,red arrow), measure that and write down the measurements. (2)
5. The difference in the measurements between (1) and (2) is "luminance scale"
6. The point measuring (1) is equal to Zone II. If luminance scale is about 7 - 9 steps, the difference in neighbor Zone is equal to the difference in exposure value. Then, it is three stepped down of measurements of (1), and is reproduced as Zone II, because measurements using spotmeter is Zone V (18% gray) reproducing value.(3)
7. Take 5 cuts of changing the exposure value between over three steps and under one step on the basis of (3)'s value.(+3,+2,+1,N,-1)
8. Repeat before process of 5 - 6 films.
Next : Darkroom Process
Necessary Tools and Chemicals
9. Three films in the exposed films develop different time.
10. Next, print those negatives.
11. Compare the those prints.
In these method, you can decide speed and development time to reproduce a luminance scale.
At actual shooting, if the luminance scale is 7 steps, you measure the deeper tone-necessary area using spoymeter, and set the value of three step down of the measurements and shoot, next develop at decided time for 7 step.