Viewfinder

A viewfinder is the small window, usually at the top of the camera, that the photographer looks through to compose a photo. It shows the scene the lens will record, so framing and focus can be checked before the shutter fires. Optical viewfinders show the real scene through glass, mirrors, or a prism. Electronic viewfinders show a live feed from the sensor on a tiny screen behind the eyepiece.

An optical viewfinder passes real light to the eye, so it has no lag, no pixels, and no battery drain. It cannot show how exposure or white balance will look. An electronic viewfinder is a small screen fed by the sensor. It previews exposure, depth of field, and color as settings change, adds overlays like a histogram or focus peaking, and brightens dark scenes. It uses more power and can lag slightly during fast action.

Almost never. A mirrorless camera has no mirror or prism to redirect light, so the sensor always sees the scene and the viewfinder is electronic. The exception is a hybrid viewfinder, found on some Fujifilm cameras, which combines an optical window with a small electronic display that can switch on or overlay information. Entry-level mirrorless cameras and most compacts drop the viewfinder and use the rear screen only.

Coverage is the share of the recorded frame visible in the viewfinder. At 100%, the view matches the final photo edge to edge. Many DSLRs offer 95% to 98%, which means a thin strip around the edges is recorded but not seen, so a stray object can appear in the photo. Electronic viewfinders show the sensor feed directly and are effectively 100%. Higher coverage makes tight framing more reliable.

The diopter is a small dial or slider next to the eyepiece. It shifts the focus of the viewfinder optics to match the photographer's eyesight, within a range of about -3 to +1. When it is set wrong, the frame and focus aids look blurry even when the lens is in focus, and glasses wearers may see a soft view. Setting it once, by turning until the viewfinder text or focus points look sharp, fixes the problem.

On a DSLR, the optical viewfinder shows the scene through the lens at its widest aperture, so a slow lens or a dim room makes the view dim too. Pressing the depth of field preview button closes the aperture and darkens it further. On a mirrorless camera, a dark electronic viewfinder usually means exposure simulation is on and the current settings would underexpose the photo, or the screen brightness is set low.

Each has a job. The viewfinder wins in bright sun, where a rear screen washes out, and it steadies the camera by bracing it against the head. It also removes distractions, since the eye sees only the frame. The rear screen wins for low, high, or awkward angles, for tripod work, and for touch focusing. Most photographers switch between the two depending on the shot.

Leaving it out saves size, weight, and cost. Phones, many compact cameras, and some entry-level mirrorless bodies compose only on the rear screen, which works well indoors and for casual use. Some of these cameras accept an add-on electronic viewfinder in the hot shoe. Photographers who shoot in bright light, use long lenses, or want a steadier hold usually prefer a built-in viewfinder.

An electronic viewfinder can. Because it displays the sensor feed at the working aperture, blur in the background appears as it will be recorded. An optical viewfinder on a DSLR shows the scene at the widest aperture, so the view looks shallower than a photo taken at f/11. Many DSLRs include a depth of field preview button, which closes the aperture and shows the true depth of field, at the cost of a darker view.

A hybrid viewfinder combines an optical window and an electronic display in one eyepiece. In optical mode it works like a rangefinder finder, showing the real scene with bright frame lines. A lever switches to a full electronic view, or overlays a small electronic panel in the corner for a magnified focus check. Fujifilm's X-Pro and X100 series use this design. It offers the clarity of glass with the previews of an EVF.