# Frame, mask and background

> How to set a clip's frame, make it follow a face, add a mask with rotation and animation, choose the background and key out a green screen in the Slicer editor.

Source: https://docs.slicer.media/en/guide/editor/frame/

During the montage the AI frames every clip by itself: it finds the face and the main subject and crops the video to the reel's aspect ratio. If you want it different — move the frame, zoom in, show a horizontal video whole or have the frame follow the speaker's face — use the **Frame** tool. **Mask** keeps only a shape in the frame visible, and **Background** sets what shows around the frame; the same panel holds **Chroma key**, which turns a green or blue screen transparent.

**Demo (Web):**

1. Click a clip and press “Frame” — the preview pauses and a hint appears on top
2. Drag the frame to the right with the mouse — another part of the scene is in view
3. Scroll the wheel — the frame zooms in
4. Click “Done” — the clip shows a manual-frame badge
5. Press “Mask” and pick “Circle”
6. Press “Background” and pick turquoise — it shows around the circle

## Frame

### 1. Turn on “Frame”

Select a clip and press **Frame**. The preview pauses inside the clip and an editing layer with a hint and buttons appears over it.

### 2. Move and zoom

**Web**

Drag the frame with the mouse — the crop window moves across the source. The mouse wheel or a trackpad pinch zooms in (up to ×3).

**iPhone and iPad**

Move the frame with your finger, pinch to zoom (up to ×3).

### 3. Fit or fill

If the source is wider than the reel's aspect ratio — for example, a horizontal video in a 9:16 reel — the editing layer has a **Fit** button. It shows the whole frame, and the empty space above and below is covered with a blurred copy of the same frame. **Fill** brings back full-screen cropping.

### 4. Done or Auto

**Done** closes the editing layer (or `Esc`). **Auto** brings back the automatic frame set by the AI.

While the frame is set by hand, the **Frame** button is highlighted and the clip shows a crop badge.

## Follow the face

When the speaker walks around, leans or gestures, a still frame keeps “losing” them. With **Follow the face** the crop window smoothly follows the face through the whole clip: it stays put while the person barely moves and gently catches up when they shift — no jerks and no jitter.

### 1. Open “Frame”

Select a clip and press **Frame**. The editing layer shows a **Follow the face** button. It's there when the frame has room to move: the source is wider or taller than the window — say, a horizontal video in a 9:16 reel or a zoomed-in frame. Photos don't have it.

### 2. Press “Follow the face”

If the AI montage has already analyzed the frames of this part closely enough, following turns on right away and for free — you'll see **The frame follows the face**. Otherwise the **Follow the face** sheet opens: Slicer finds the face in the clip's frames and then builds the frame's motion from it.

### 3. Choose where to look for the face

**Web**

On the web an AI in the cloud looks for the face: press the button with the price — “Find the face · ≈ N tok.”. The **On device** option is disabled and labeled **In the app**.

**iPhone and iPad**

In the **Where AI runs** row:

-   **On device** · free — Apple Vision looks for the face on your phone, tablet or Mac; the button reads **Find the face · free**. **On the device, the video does not go to the cloud.**
-   **In the cloud** — an AI service at cost, the button shows the price.

What's selected by default is set in **Profile** → **Where AI runs** ([more](https://docs.slicer.media/en/guide/account/preferences/#ai-where)). On the device, faces are found only in videos uploaded from that same device; otherwise — **The videos were uploaded from another device — only the cloud is available here.**

While the search runs you'll see **Looking for the face…**, and in the app — **Looking for the face on the device** with a percentage above the preview. Once the face is found, the frame starts following it straight away.

### 4. Adjust the frame if needed

The editing layer's hint changes to **The frame follows the face. Drag it with the mouse to adjust it at this moment** (in the app — with your finger). Move the playhead to the spot you want and drag the frame: the motion changes at that moment only, and the rest of the following stays as it was. Zooming with the wheel or a pinch applies to the whole clip.

**Stop following** turns following off: the frame stays still where it was at the playhead. **Auto** brings back the AI's automatic frame.

-   **A clip of up to 2 minutes.** If it's longer, the sheet says **The fragment is longer than 2 minutes — split it to follow the face**: [split](https://docs.slicer.media/en/guide/editor/fragments/) the clip and turn on following for each part.
-   **If there's no face** — **No face found in this fragment**, and the frame doesn't change.
-   **A found face is remembered** for the source: following on another clip from the same seconds turns on right away and for free.
-   **The cloud price** is at cost: one AI call per 10 seconds of the clip (the AI looks at two frames per second) — ≈0.97 tokens per call. The sheet shows the price before you start — “≈ price, up to a limit”; if it doesn't work out, no tokens are charged. On the device it's free.
-   The face search is recorded in the [project history](https://docs.slicer.media/en/guide/projects/history/) as **Face tracking**.

## Mask

A mask keeps a shape in the frame visible and shows the clip's background outside it (more on that below). It works for striking inserts, a “window” in the frame or emphasis on a face.

### 1. Pick a shape

Select a clip and press **Mask**. The preview pauses inside the clip. Pick a shape: **Circle**, **Frame** (a tall rectangle with rounded corners), **Heart** or **Stripe** (a full-width horizontal band). **None** removes the mask.

### 2. Set the look

-   **Size** — 20 to 100, 70 by default;
-   edge **Feather** — 0 to 100, 10 by default;
-   **Rotation** — −180° to 180°;
-   **Invert** — the other way round: video outside the shape and the clip's background inside.

### 3. Put the shape in place

The mask doesn't have to stay in the center — you can move it right on the preview.

**Web**

**Drag the shape on the preview, scroll to resize.** Rotate it with the **Rotation** slider in the panel.

**iPhone and iPad**

**Drag the shape, pinch to resize, twist to rotate.**

A badge on the preview shows the shape's size, and in the app its rotation too.

### Mask animation

The shape can travel across the frame: follow an object, open up or spin. It works like [keyframes](https://docs.slicer.media/en/guide/editor/keyframes/).

1.  Move the playhead to where the shape should start moving and press **Animation point**.
2.  Move the playhead further and drag, resize or rotate the shape — a new point appears there.
3.  Between points the shape moves smoothly. The hint in the panel shows how many points the mask has, for example **Animation points: 3. An edit under the playhead adds a new one — the shape moves between them.**

When the playhead is on a point, **Animation point** becomes **Remove point**. Position, size and rotation are animated; the shape, feather and inversion are shared by the whole clip. A mask can have up to 24 points.

## Background

**Background** is what shows where the frame doesn't cover the screen. The hint in the panel says: **Shows around a fitted, zoomed-out or sliding frame and outside the mask.**

-   **Blur** — a blurred copy of the frame. It shows around a frame fitted whole (**Fit**). Outside a mask and around a zoomed-out, rotated or sliding frame you get black instead of the blur.
-   Ten colors: black, white, graphite, turquoise, blue, beige, coral, yellow, dark green and purple — a color shows wherever a background is needed.

**Apply to all clips** sets the selected background for the whole reel. With nothing selected, the **Background** button opens the panel for the clip at the playhead.

The background also matters for [Remove background](https://docs.slicer.media/en/guide/ai/remove-background/): there, **Blur** or a color is what ends up behind the person.

## Chroma key

If a video was shot against a green or blue screen, you can remove it without AI and for free: the screen turns transparent, and a color or a photo shows behind the person. The hint in the panel says: **A green or blue screen turns transparent, with a colour or a photo behind. Free.**

### 1. Turn on “Chroma key”

Select a video clip and press **Background**. Below the background colors is the chroma key section: press **Chroma key**. Slicer picks the screen color from the edges of the frame by itself, and a swatch of it appears next to the button.

### 2. Refine the color if needed

-   **Auto** — pick the color from the frame edges again, at the playhead;
-   **Eyedropper** — take the color from a point on the preview: **Click the screen in the preview** (in the app — **Tap the screen in the preview**).

### 3. Tune the edge

-   **Similarity** — how close to the key a shade still gets removed (5 to 50, 15 by default). Patches of the screen remain — raise it; hair or clothes start to vanish — lower it.
-   **Smoothness** — edge softness (0 to 30, 10 by default).
-   **Remove fringe** — takes the green or blue spill off the edges of the figure (on by default).

### 4. Choose what goes behind

-   A color — from the row of colors above in the panel: **Behind — a colour from the row above or a photo.** With **Blur** selected, black goes behind.
-   **Background photo** — any image in the project: the photo tiles next to **Colour**. If there are no photos yet — **Add a photo in Media — it can become the background.** ([Your own photos and videos](https://docs.slicer.media/en/guide/editor/media/)).

Press **Chroma key** again to turn it off. The chroma key shows in the preview right away and looks the same in the export. It's available on video clips — photos and freeze frames don't have it.

> **Tip.** Chroma key works best on an evenly lit screen without folds or shadows, with the person standing a couple of meters in front of it and not wearing its color. If the background is an ordinary one rather than green, use [Remove background](https://docs.slicer.media/en/guide/ai/remove-background/).

## Good to know

-   Frame, mask, background and chroma key show in the preview right away and are free. Only the face search in the cloud is paid.
-   A zoomed-out frame isn't only from the **Zoom out** animation: a [keyframe](https://docs.slicer.media/en/guide/editor/keyframes/) with a scale below 100% or a rotation also reveals the background around it.
-   **Replace** resets a manual frame — the new source is framed automatically ([Freeze frame, replace…](https://docs.slicer.media/en/guide/editor/freeze-replace/)).
-   In a different [aspect ratio](https://docs.slicer.media/en/guide/editor/format-cover/) the frame is recomposed for the new proportions.

## What's next

-   [Keyframes and By frame](https://docs.slicer.media/en/guide/editor/keyframes/)
-   [Remove background](https://docs.slicer.media/en/guide/ai/remove-background/)
-   [Aspect ratio and cover](https://docs.slicer.media/en/guide/editor/format-cover/)