What you're aiming at
A full range of tone: a deep black that still holds detail, a bright white that still holds detail, and all the values in between. That was hard to achieve in the darkroom and it is still hard now.
The Zone System, briefly
Ansel Adams' system divides the tonal scale into zones from pure black to pure white, with middle grey in the centre. The practical value today isn't the film-era mechanics — it's the habit of deciding in advance which zone a given part of the scene should land in, and exposing so that it does.
- Your meter always wants to make what it reads middle grey. Every exposure decision is really a decision about where to move a tone away from the middle.
- Meter a bright rock and it becomes grey — you must add exposure to put it back where it belongs. Meter dark bark and it becomes grey — you must subtract.
- The digital equivalent of the zone ruler is the histogram: it shows where the tones actually fell.
Evaluating a colour scene for mono
The skill most photographers are missing is identifying which colour scenes will convert well. Ask:
- Is there tonal separation, or only colour separation? Two colours of the same brightness — a red flower on green leaves — become the same grey. Colour was doing all the work, and mono removes it.
- Is there texture or structure for the light to reveal? Mono lives on form, texture, line and shape.
- Is the light directional? Side and back light build the tonal range mono needs. Flat frontal light gives a flat grey.
- Is there a genuine black and a genuine white in the frame? Without both anchors, the image reads muddy.
On the a7R III, set a mono Creative Style so the finder and rear screen preview in tone while RAW keeps the colour data — the fastest way to train the eye.
Taking control of tone
- In camera: choose the exposure that protects the highlight you can't rebuild, then let the shadows fall — the sensor recovers shadow far better than clipped highlight.
- Watch Zebra for the whites you intend to keep detail in.
- In processing: the conversion method matters less than the decisions — which colours become which greys, where the black point sits, and how much local contrast the subject can carry.
- Toned monochrome vs black and white are different things. Decide which you're making before you start.
Practice
- Photograph one scene and place a chosen mid-tone deliberately: meter it, then decide whether it should be lighter or darker than middle grey and compensate.
- Photograph a scene that works in colour but that you predict will fail in mono. Convert it and confirm why.
- Photograph the same subject in flat light and in strong side light; compare the histograms, not the pictures.
Consolidated from references: Kent DuFault, Better Black and White (The Zone System; Evaluating a Colour Scene for Tone; Taking Control of Tone); Digital Black and White Photography.