A camera optical viewfinder is a small window on a camera that allows the user to frame and compose a shot by looking through it. Typically uses a system of mirrors and lenses (SLRA single-lens reflex camera (SLR) is a camera that typically uses a mirror and prism system (hence "reflex" from the mirror's reflection) that permits the photographer to view through the lens and see exactly what will be captured. With twin lens reflex and rangefinder cameras, the viewed image could be significantly different from the final image. When the shutter button is pressed on most SLRs, the mirror flips out of the light path, allowing light to pass through to the film. Other camera typoes include DSLR, Rangefinder and Compact. and DSLRA digital single-lens reflex camera (digital SLR or DSLR) is a digital camera that combines the optics and the mechanisms of a single-lens reflex (SLR) camera with a digital imaging sensor. The reflex design scheme is the primary difference between a DSLR and other digital cameras. In the reflex design, light travels through the lens and then to a mirror that alternates to send the image to either the viewfinder or the image sensor. The viewfinder of a DSLR presents an image that will not differ substantially from what is captured by the camera's sensor but presents it as a direct optical view through the lens, rather than being captured by the camera's image sensor and displayed by a digital screen. DSLR is often (wrongly) used to describe cameras that are Micro Four Thirds or Bridge Camera - just because they look similar. This can bee seen when cameras are offered for sale. ) to show the view through the camera's lens, giving a real-time, optical representation of the scene. On simple cameras it is just a lens that roughly lines up with the frame, but may not be accurate and may not change with a zoom lens. This can be especially useful in bright lighting conditions or when shooting fast-moving subjects where using the camera's digital screen may be difficult.
