Offline Mode starts when you take a snapshot or load a photo. The camera stops and the readings hold still, which is what makes everything on this page possible: in live mode the app is tracking a moving scene, and here it is measuring one fixed image precisely.
Getting in and out
- From the camera — tap the shutter button. The frame freezes, cropped to the film format you selected.
- From the library — tap the photo button and choose an image. The app reads the photo’s EXIF aperture, shutter speed, ISO and date, and meters the full frame: a photo is already the shape it is, so no format crop is applied.
- Back to live — tap the green LIVE button at the top left. The camera restarts, and the custom spots and overlays on the frozen frame are cleared.
Adaptive Zone
The Adaptive Zone control decides where the boundary between shadow, midtone and highlight falls — which is to say, what the app considers the darkest and brightest parts of this scene.
| Mode | How the boundaries are chosen |
|---|---|
| 2% | By percentile: the darkest 2% and brightest 2% of pixels. The default, and predictable — it always brackets the same proportion of the frame. |
| Otsu | By multi-class Otsu thresholding, which finds the natural tonal clusters in the image. Follows a scene that genuinely separates into dark and light masses. |
| Manual | Two sliders, set by you. |
Changing the mode moves the Highlight and Shadow spots, and the midtone EV follows, so the exposure calculator updates with it.
Spot meters
Each of the three built-in spots is labelled Auto or Manual:
- Drag a reticle to re-meter any point. That spot becomes Manual. The highlight reading is held at or above the midtone, and the shadow at or below it, so the three cannot cross over.
- Reset returns a spot to its automatically detected position and to Auto.
- Tap anywhere else on the image to add a custom spot — a smaller reticle showing the EV at that point, coloured on a scale from blue through green to red by where it sits between shadow and highlight.
- Tap a custom spot to remove it.
Custom spots are how you answer the question the three built-in readings cannot: not “how bright is the brightest thing”, but “how many stops below the midtone is that face, that wall, that patch of shadow”.
A dot (•) on an EV label means it has been corrected to your reference meter.
Overlays
Three overlays toggle independently, and all three regenerate whenever you change ISO, move a spot, or adjust the adaptive zone.
Heatmap — a semi-transparent colour map of brightness across the whole frame, blue through green to red. Shows where the tones are, which the three spot readings cannot.
Histogram — the luminance distribution, with dashed S, M and H markers at the shadow, midtone and highlight boundaries. Shows how much of the frame sits at each brightness, and whether the tones are bunched or spread.
Zone Map (V) — posterizes the frame into the eleven Adams zones, from pure black to pure white. Shows which zone each region actually lands on. This is the overlay to check before you commit an exposure: if the thing you metered as Zone V is rendering as Zone III on the map, you are about to place it wrong.
Read the overlays and the spots together. The overlays give the spatial picture; the spots give the numbers.