# A frame that fits the window it recorded > Solid, gradient or picture backdrops, padding, shadow, and corners that match the recorded window's own measured radius so the frame lands on its edges. *Source: https://lumae.app/features/backgrounds.md. This page in HTML: https://lumae.app/features/backgrounds.* Padding and a backdrop turn a raw capture into something you can put on a landing page. The hard part is the corners: guess the radius and the frame sits a pixel off the window's own edge, which is exactly the sort of thing nobody can name but everybody sees. ## At a glance - **Corner detection:** 5 agreeing frames, within 2 s - **Corner curve:** continuous, three Bézier - **Edge inset:** 1.5 source pixels - **Backdrops:** solid, gradient, picture - **Per-clip overrides:** background, padding, radius, shadow - **Shadow:** resolved as a fraction of the frame ## Corners measured, not guessed When Lumae records a single window it leaves the window's shadow out and watches the live frames for the shape of the transparent cut-out at each corner, cross-checking all four until five frames agree, within the first two seconds. The median radius is stored on the recording and scaled by the fit, so the frame lands on the window's real edge whatever size you render at. The curve itself is Apple's continuous three-Bézier corner, the one macOS uses for its own windows and icons, rather than a quarter circle. Side by side the difference is a visible kink, which is why a frame built on the wrong curve never quite looks native. ## Backdrops A backdrop is a solid colour, a linear gradient, one of the bundled paintings, or a picture of your own. Gradients state their direction once in the project, so the swatch you pick from and the frame you render match without a second implementation to keep in step. Pictures are decoded once per distinct image and cached, aspect-filled and cropped to the canvas, which keeps the cost of a photographic backdrop the same whether the export is 720p or 4K. ## One look, with per-clip exceptions The video has a look; a clip may depart from it. Background, padding, corner radius and shadow are each optional on a clip, and leaving one unset means it follows the video. So the empty style is the common case, and two clips can be framed differently in one export when you want the contrast. The way back up is a single action: make one clip's choice the video's, and it is cleared from every clip in the same undo step. Splitting a clip keeps the look on both halves. ## The frame moves with the camera Because the zoom is a camera move over the finished frame rather than a magnification of the video inside it, padding and the backdrop scale with the picture and slide out of view as the camera pushes in. Captions are drawn after the zoom and stay where they are. One more detail worth the pixel it costs: a window capture's outermost pixels are anti-aliased against a clear background that the encoder stores as black, so Lumae cuts 1.5 source pixels inside the window's edge. Without it, a faint dark rim traced the corners. ## Questions ### Can I use my own background image? Yes. Choose an image in the Look tab and it is copied into the project package, so the project stays self-contained and still renders on another Mac. ### What if Lumae measures the corner radius wrong? Set it yourself. A radius you choose on a clip also switches off corner matching for that clip, so your number is the one used. Full-screen and area recordings have no window corners to measure and start square. ## Related - [Screenshots](https://lumae.app/features/screenshots.md): Capture and annotate, with every mark still editable later. - [Automatic zoom](https://lumae.app/features/automatic-zoom.md): Clicks become camera moves, with the timing worked out for you. - [Export](https://lumae.app/features/export.md): MP4, MOV, ProRes and GIF, from the renderer the preview uses.