Long before the invention of photography, artists had made an imaging device, which placed a mirror in the middle of the table with frosted glass on it, which could accurately describe the scenery outside the window. 186 1 year, Thomas Satton, an Englishman, invented a camera with a similar structure, and installed a 45-degree reflector between the photographic lens and the photosensitive element. Since then, this camera that takes pictures with the same lens has become a unique image recording tool. However, such a camera that does not produce parallax did not develop rapidly at the beginning of last century because of its miniaturization. At that time, whether Germany, a big camera manufacturing country, or Japan, which came from behind, the products of small and medium-sized civil cameras were mainly paraxial framing or double-lens reflection (another form of paraxial framing).

1934 1 month, Japan Seiki Optical Co., Ltd., the predecessor of Canon, introduced a wide-range camera, which is a paraxial camera. After using 135 film to design and manufacture as many as 32 advanced paraxial cameras, Canon began to participate in the competition of small SLR cameras (SLR) in 1959. Because in this era, all mainstream camera manufacturers seem to realize that single-lens reflex cameras are about to become the new mainstream camera products.

Single-lens reflex camera has many advantages that paraxial camera can't match: no parallax; It can replace all kinds of photographic lenses with different specifications and uses; Can maximize the automation of shooting; Can cooperate with various auxiliary systems for different purposes; It will be more versatile than other types of cameras. With the arrival of digital images, SLR cameras are developing continuously in this brand-new image recording mode. From film to digital, the ancient single-lens reflex camera has entered a new era of digital image. The abbreviation of single-lens reflex camera is Single Lens Reflex, and the name of digital SLR camera only needs to add a D (Digital)!