Viseur

Viseur is a device that aligns the user’s line of sight with a target or image. In French, the term covers aiming devices on weapons as well as viewfinders on cameras and other optical instruments. The English equivalents are sight (for firearms) and viewfinder (for imaging devices).

In firearms, a viseur consists of two main elements: a front sight and a rear sight. Iron sights use a front post or blade and a rear notch or aperture, and they may be fixed or adjustable for windage and elevation. Optical sights include telescopic rifle scopes, red-dot sights, and holographic sights, which provide magnification or a reticle for aiming. Zeroing or sighting-in is the process of adjusting the sight so that the point of aim matches the projectile’s trajectory at a given distance. Sights vary in durability, field of view, and reticle design, with specialized variants such as night sights for low-light use.

In cameras and other imaging devices, viseur refers to the viewfinder—the component through which the user frames the image. An optical viewfinder uses a prism or mirror system to present the scene, while electronic viewfinders display a digital image from the sensor. Some devices use an electronic viewfinder, an LCD or OLED screen, instead of or in addition to a traditional optical system. Viewfinders are essential for composing shots, estimating framing, and, in some cases, adapting exposure and focus.

Beyond weapons and imaging, the term can be used for any device that provides a sighting line or visual framing, including surveying and surveying-related instruments.