viewfinder

A viewfinder is a device on a camera or other imaging instrument that enables the user to frame and, in some cases, focus and preview the image before capture. It serves as the user’s optical or electronic interface to the scene being recorded, helping with composition, framing accuracy, and sometimes exposure preview.

Optical viewfinders use a direct optical path from the scene to the eye. In single-lens reflex cameras, a reflex mirror and a pentaprism or pentamirror relay the image to the viewfinder, providing through-the-lens framing without electronic display. OVFs offer immediate, lag-free viewing and function independently of battery life, but they can appear dim in low light and may show parallax error in nonthrough-the-lens designs or at close distances.

Rangefinder viewfinders are separate from the lens and rely on a coupled or uncoupled focusing mechanism that superimposes or aligns a frame in the finder with the subject. They were common in classic compact and rangefinder cameras and excel at compact designs and discreet shooting, but framing precision can change with distance, and they are less common in modern interchangeable-lens systems.

Electronic viewfinders render the scene on a small digital display (LCD or OLED) that is fed by the camera’s sensor. EVFs allow exposure previews, focus peaking, magnification for manual focus, and information overlays, and they work in bright or dim lighting with the caveat of potential lag and higher power consumption.

Viewfinders are also used in video cameras, projectors, microscopes, and binoculars. In contemporary photography, many mirrorless cameras rely on EVFs, while DSLRs continue to use optical viewfinders, reflecting a trade-off between immediacy, information, and power use.