Zone System

The Zone System panel shows a black and white photo’s tones as eleven zones, from pure black to pure white. You can see where every tone in the picture falls, move tones to the zones you want them in, and fine-tune any band of tones on its own.

What it is

The Zone System was devised by Ansel Adams and Fred Archer in the 1930s to take the guesswork out of black and white photography. It divides the range from black to white into eleven zones, written in Roman numerals:

Each zone is one stop (twice the light) brighter than the one below it. Zone V is middle gray, so zone VI has twice its light and zone IV half.

Immage measures the zones on the black and white image in scene-referred light, before the tone mapper. So the zones describe the light in the scene, and the pixels the histogram counts, the pixels the overlay shows and the pixels a zone adjustment changes are always the same ones.

The objective

Adams’ idea was previsualization: decide what the finished print should look like, then work back to get there. With the Zone System you think in terms like “the shadow under that rock should be dark but still show texture” and turn that into “that shadow belongs in zone III”.

Editing with the panel follows the same idea:

1. Decide where the important tones should sit. For a portrait, the lit side of the face often belongs in zone VI; for a landscape, the textured shadows in III and the brightest snow or cloud with detail in VII-VIII.
2. Read where those tones fall now. Point at the zones and watch where they light up on the photo.
3. Place them, moving a tone and the tones around it to the zone you chose.
4. Refine a single band of tones, or one band in one part of the photo, where moving everything together isn’t enough.

Keep two things in mind as you go:

• Texture lives in zones II to VIII. Anything pushed into 0-I or IX-X loses its detail. Sometimes that’s what you want (a black background, a glowing window), but it should be a choice, not an accident.
• Keep tones in order. A brighter part of the scene should stay brighter than a darker one. If tones cross over, edges get halos and smooth gradients break into bands. The panel warns you when an edit would do this.

Opening the panel

Click the Zone System button on the rail, the column of buttons on the right edge of the window.

The Zone System works only on black and white photos. If the photo is in color, the panel says so and offers Convert to Black & White. That’s the same as setting Treatment to Black & White in the Adjust panel.

Reading the zones

The zone histogram

At the top is a bar for each zone, 0 to X, shaded from black to white. A bar’s height shows how much of the photo falls in that zone. A thin line over the bars shows the same distribution in finer detail, in tenths of a zone.

If any of the photo is darker than zone 0 or brighter than zone X, the percentages show under the histogram: ◀ on the left for the part darker than zone 0, ▶ on the right for the part brighter than zone X.

After an edit, the bars dim for a moment while the zones are measured again.

Pointing and pinning

• Point at a zone: it lights up over the photo in the overlay color, so you can see exactly which parts of the picture are in that zone.
• Click a zone to pin it. The tabs below work on what is pinned. Click the pinned zone again to unpin it.
• Drag across the bars, or shift-click a second zone, to pin a run of zones (for example, zones III-V).
• Point at the photo: the zone of the spot under the pointer lights up in the histogram, and pointer under the thumbnail gives it exactly, such as zone VI.3. Past zone 0 or X, the ◀ or ▶ figure lights instead.

The inspector

Below the histogram, a small grayscale thumbnail shows the pinned (or pointed-at) zones as a mask: white where the photo is fully selected, black where it isn’t, and gray at the soft edges. Next to it:

• the zone or zones selected, marked (hover) while you’re only pointing
• % of the image: how much of the photo they cover
• mean: their average zone. A value such as V.4 means four tenths of the way from zone V to zone VI.
• image: median … 5-95% …: where the middle of the whole photo sits, and the range that its darkest 5% and brightest 5% fall outside of. This is a quick check of the photo’s overall tonal range.

Show mask overlay

When Show mask overlay is on, the pinned zones stay highlighted on the photo. It steps aside while you drag a slider, so you can see the result. The zone you are pointing at always shows, whatever this switch is set to. Press O to turn the overlay on or off.

Placement: moving tones to new zones

The Placement tab moves the pinned zones to other zones. It works like a tone curve, but you describe the move in zones. The tones around the pinned zones follow, fading out with distance, so the picture stays smooth.

Placement is one curve for the whole photo. Each move you make builds on the ones before, so you can place the shadows, then the highlights, then the midtones.

The curve

The graph shows, for each zone across the bottom, which zone it comes out in. The diagonal is “no change”. Where the curve is above it, tones are brighter; below it, darker. The pinned zones are shaded.

Above the sliders, a readout such as Zone III → IV.2 (comes out at IV.1) says where you asked the pinned zones to go and where they actually land. The two can differ a little, because the curve has to stay smooth and keep tones in order.

Controls

• Place at: the zone the middle of the pinned zones goes to. You can move it up to two zones either way. To make shadows that fell in zone II hold texture, pin zone II and place it at III.
• Transition: how many zones on either side follow the move, from 0.5 to 4 (1.5 by default). A small value moves only what is pinned, which takes contrast out of the zones next to it. A large value moves a broad sweep of tones together, which feels more like an exposure change.
• Reset placement: undo all placement. Local adjustments stay.

Notes you may see

• zones 0 and I move with zone II: zones 0 and I can’t be placed on their own. Pinning them moves them together with zone II.
• transition widened to … zones to keep tones in order: the move was too sharp for the transition you set, so Immage used a wider one to keep brighter tones brighter.
• tones cross over near zone …: widen the transition: somewhere a brighter tone now comes out darker than a darker one. Increase the transition, or move the zones less.

When the photo has a placement, a dashed line on the histogram shows where the tones were before it. Compare it with the solid line to see what the placement did.

Local: adjusting a band of tones

The Local tab adjusts only the pinned zones, through a mask that selects them. Use it when placement isn’t precise enough. For example, you might add contrast inside zones VI-VII to bring out cloud texture, or darken zone IV only in the sky.

The first time you move one of its sliders, Immage creates a mask named after the zones, such as Zone VI or Zones III-V. These are ordinary masks: they also appear in the Masks panel, and undo treats them like any other edit.

Saved adjustments

Each zone mask you’ve made shows as a chip at the top of the tab. Click one to pin its zones again and carry on editing it, or click × to delete it.

Color mask: narrowing to part of the photo

Color mask restricts the adjustment to part of the photo as well as to the pinned zones:

• All: the whole photo (the default)
• Sky, Rocks, Vegetation, Subject: a part Immage’s AI finds in the photo. It looks at the photo’s original colors, so it can tell a gray sky from gray rock even when they share a zone.
• + Object: any one thing in the photo. Click + Object, then drag a box around the object on the photo, or click it, and the AI outlines what is there (Esc cancels). Each object gets a button of its own, Object A, Object B and so on, for choosing it again.
• everything but it: appears once you’ve chosen a part, and selects the rest of the photo instead (for example, zone V everywhere except the sky)

The first time you choose a part on a photo, it takes a moment to find. If the photo has no such part, the status bar says nothing found and the choice stays as it was.

Choosing a part changes only the overlay at first. Like any zone mask, the mask is created when you first move a slider, and it is named for both the zones and the part, for example Zone V · Sky or Zone V · not Sky. It is a mask of its own: a Zone V mask you made before stays as it was, so to move an adjustment to the sky, set it on Zone V · Sky and return the sliders of Zone V to zero. The overlay and the thumbnail show the combined selection.

A part changes only where it overlaps the pinned zones. A bright sky may sit in zones VIII-X, so with zones III-VII pinned, Sky selects nothing and the sliders have no effect. Check the overlay: if it shows nothing over the part, pin zones that it covers.

Controls

• Exposure: brighten or darken the selected tones, by up to ±2 EV (stops).
• Contrast: from -100 to +100. It spreads the selected tones apart or draws them together around the middle of the pinned zones, so the zones’ overall brightness holds while texture within them strengthens or softens.
• Mask strength: how much of the adjustment is applied, from 0 to 100%. Lower it to tone the adjustment down without changing the sliders.
• Transition: how softly the mask fades into the neighboring zones, from 0.1 to 2 EV (1 by default). Narrow values select the zones sharply; wide ones blend more gently.
• Edge aware: from 0 to 100. Makes the mask follow the edges in the photo, so a change to the sky doesn’t spill over onto a dark tree against it as a halo.

When tones turn around

If you see this much exposure turns tones around at the zones’ edge, the exposure pushes the selected tones past the tones just outside the mask. Brightening zone IV by two stops, for example, takes it beyond parts of zone V that weren’t brightened. To fix it, widen the Transition, lower the Mask strength, or make the move on the Placement tab, which always keeps tones in order.

Placement or Local?

• Use Placement to set the overall tonality of the photo: where the shadows, midtones and highlights sit. It changes the whole range smoothly and can’t reverse tones.
• Use Local for targeted work: texture within one band, one zone in one part of the photo, or a change too narrow for placement.

Advanced

Click Advanced at the bottom of the panel for:

• Overlay color: blue, red, green, yellow or magenta. Choose whichever stands out best against the photo.
• Overlay opacity: from 10 to 100%.
• Reset zones: removes the placement and every zone adjustment from the photo. Your other edits stay.

Immage remembers the overlay settings between photos and sessions.

Keyboard

If nothing is pinned, an arrow key pins zone V.

A worked example

A landscape with a bright sky and a shaded foreground:

1. Open the Zone System panel and Convert to Black & White.
2. Point at the zones. Say the foreground rocks light up in zone II and the clouds in zone IX: the rocks have lost texture and the clouds are nearly white.
3. Pin zone II. On Placement, set Place at to III. The rocks move up a zone and their texture comes back.
4. Pin zone IX and place it at VIII to bring tone back into the clouds.
5. The clouds still look flat. On Local, pin zones VII-VIII, choose Sky under Color mask, and raise Contrast to bring out their structure. Add some Edge aware if a halo appears where the sky meets the hills.
6. Check the ◀ ▶ percentages under the histogram. Only what you mean to be pure black or pure white should be there.

This page is part of immage's own docs, at v0.41.1. View the source on GitHub.