Camera Control (iOS 18+)# PRO

iOS 18 introduced the Camera Control — the dedicated hardware button on iPhone 16 (and on-screen control surface on other devices) that lets people adjust capture settings without diving into your UI. AVFoundation models this as a list of AVCaptureControl instances attached to the running AVCaptureSession. Scripting bridges all of them.

#Detecting support

The hardware Camera Control only ships on iPhone 16 and later. Always feature-detect:

if (!session.supportsControls) {
  // Fall back to plain on-screen UI; do not call addControl/setControlsDelegate.
  return
}
console.log(`max controls: ${session.maxControlsCount}`)

session.supportsControls is safe to call on older devices — Scripting wraps it with a respondsToSelector check so it just returns false rather than crashing.

#Built-in system controls

The two most common controls are provided by the system; pass the device they should bind to:

const camera = AVCaptureDevice.default("video")!
const zoom = new AVCaptureSystemZoomSlider(camera, value => {
  console.log("zoom →", value)
})
const exposure = new AVCaptureSystemExposureBiasSlider(camera, value => {
  console.log("exposure bias →", value)
})

session.configure(() => {
  if (session.canAddControl(zoom)) session.addControl(zoom)
  if (session.canAddControl(exposure)) session.addControl(exposure)
})

The system writes the zoom factor / exposure bias straight back to the device for you. The action callback is purely informational — use it to update your own UI.

#Custom slider

Continuous, stepped, or discrete-values:

// Continuous, formatted as ƒ-stops
const aperture = new AVCaptureSlider("Aperture", "camera.aperture", {
  range: [1.2, 16],
  defaultValue: 1.8,
  localizedValueFormat: "ƒ%.1f",
})

// Stepped (discrete) slider
const evStep = new AVCaptureSlider("EV", "sun.max", {
  range: [-2, 2],
  step: 0.33,
  prominentValues: [-1, 0, 1],
})

// Pre-defined values
const iso = new AVCaptureSlider("ISO", "circle.fill", {
  values: [50, 100, 200, 400, 800, 1600, 3200],
  defaultValue: 200,
  localizedValueFormat: "ISO %.0f",
})

aperture.setActionHandler(value => updateAperture(value))

Pass any SF Symbols name; Scripting does not validate it. If the symbol cannot be resolved at runtime the control simply renders without an icon.

#Custom index picker

Use this when titles are non-numeric or non-uniform:

const wb = new AVCaptureIndexPicker("White Balance", "camera.filters", {
  localizedIndexTitles: ["Auto", "Daylight", "Cloudy", "Tungsten"],
  defaultIndex: 0,
})
wb.setActionHandler(index => applyWhiteBalance(index))

#Adding controls to the session

addControl(...) follows the same rules as inputs/outputs: prefer configure(...) so the changes commit atomically. Adding more than maxControlsCount is a no-op (canAddControl returns false).

session.configure(() => {
  if (session.canAddControl(zoom)) session.addControl(zoom)
  if (session.canAddControl(aperture)) session.addControl(aperture)
  if (session.canAddControl(wb)) session.addControl(wb)
})

#Receiving lifecycle events

AVCaptureSessionControlsDelegate tells you when the system Camera Control UI shows / hides — useful for dimming your own overlay while the system control is on screen.

session.setControlsDelegate({
  didBecomeActive: () => setSystemControlVisible(true),
  willEnterFullscreenAppearance: () => setOverlayDimmed(true),
  willExitFullscreenAppearance: () => setOverlayDimmed(false),
  didBecomeInactive: () => setSystemControlVisible(false),
})

Pass null to remove the delegate.

#Hooking the hardware button to capture

The hardware Camera Control button does not dispatch through your control delegate by default — you must attach an AVCaptureEventInteraction. Without it, half-presses and full-presses are silently swallowed:

const interaction = new AVCaptureEventInteraction((phase, kind) => {
  if (phase === "ended" && kind === "primary") {
    photoOutput.capturePhoto({ codec: "hevc" })
  }
})
interaction.attach()

// when leaving the page:
interaction.detach()

phase is "began" | "ended" | "cancelled". kind is "primary" for the main press and "secondary" for half-press / focus events.

#Common pitfalls

• Delegate never fires. You forgot setControlsDelegate(...), or the session never started running.
• Hardware press does nothing. You forgot new AVCaptureEventInteraction(...).attach().
• supportsControls is false. Either you are on a device without the hardware Camera Control, or the session has not been configured yet — always check after addInput(...).
• Custom slider does not show. Either the SF Symbol name is wrong, or maxControlsCount is exceeded — Scripting silently drops the addControl call in both cases.