Monitor displays full frame including overscan area — essential to see what's actually recorded. Broadcast and cinema standard.
The monitor displays the entire recorded image material—not just what the viewer will eventually see. This is the crucial difference from normal preview displays, which already show a cropped image. On set or in the edit, you need this complete view to control what actually ends up in the recording. Underscan is indispensable, especially for broadcast standards or when shooting for multiple formats (cinema, TV, digital).
In practice, it works like this: The monitor is explicitly switched to underscan mode—on most professional displays (SmallHD, Atomos, Blackmagic) via menu or hardware button. The screen then shows 100% of the recorded frame, including the so-called overscan area, that zone at the edge of the image which is cropped during standard broadcast playback. You see exactly what falls off at the edges, whether a microphone boom unintentionally enters the frame, or how tight your composition really is. This isn't academic—it regularly saves your production design and boom operators from nasty surprises.
Underscan is particularly critical in several scenarios: Broadcast production (HD, 4K for television)—here there are strict safe-action and safe-title areas, and underscan shows you which ones are being exceeded. Cinema projects with DCI mastering—the pixel formats differ, and underscan reveals what is lost during reframing. Even with VFX shots, you need to know where the compositor will have no more room—underscan makes this visible. In contrast, a normal monitoring display (like on many camera LCDs) already works with overscan, thus cropping the image edges and suggesting a finished composition that isn't there yet.
Practical tip: Use underscan combined with your monitor's safe guides (often activatable as an overlay)—this way you simultaneously see where the safe area begins and where critical details lie. If you're delivering for different final formats, an underscan monitor at the video village is your best friend. The DoP and director can then see in real-time what compromises they are making when framing the image wider or tighter.