Crop factor is a term that has added to the dictionary of photographic terms the emergence and widespread use of new-generation cameras. With the development of modern innovative technologies, more and more SLR digital cameras have appeared on the market with a cost affordable for non-professionals. Such buyers, in addition to the price, distinguish perhaps another category for which they choose a camera - this is the number of megapixels. They already figured out the megapixels and, vaguely imagining what it really is, they nevertheless understand that the more there are, the better the device. However, as it turned out, another important characteristic that distinguishes the quality of digital cameras among themselves is the crop factor. Before you buy a camera, you should still figure out what it is.
Few amateur photographers have at least once wondered, why, if the lens and lenses are round, do they take a rectangular frame? There is nothing complicated in answering this question. When projecting a photographed image onto a medium in the camera, the lens optics simply cuts off the "excess" part of the image, giving it a rectangular shape. This is very convenient for the production of film, consisting of a number of rectangular frames, and for the manufacture of photographs, giving both one and the other compactness and versatility.
Due to the long-term use of film photography, the frame size on the film continues to be used as a reference size. Nobody even thinks of changing it even now, when shooting on film is almost a thing of the past. Nowadays, with the advent of digital photography, shooting is carried out on a special matrix, which can conditionally be compared with a film.
The matrix, which in size corresponds to the film frame, is called full-length. However, most digital SLR cameras have matrices with a size significantly smaller. Naturally, on such matrices, only the central region of the image, which could get onto the full-format matrix, is captured. Visually, it looks as if the frame was photographed by a lens having a much greater focal length.
This is where the term came from that defines the “increase” in focal length, which actually does not occur, because here, as in our example with round optics, the outer part of the frame is simply cut off. In English, the word "crop" (crop) is translated as "cut off". Hence the name of the term - crop factor, which denotes such an artificially increased focal length. This accurately describes in this case how the shooting process actually takes place, since in the physical sense the focal length of the photo lens has not changed, but only the angle of view has changed.
So, the frame size of a 35-mm film of 24x36 mm was and remains the reference, with which the crop factor is now associated. For such a frame, it equals 1. At the very beginning of the digital photography era, Nikon wisely decided that it was possible to produce digital SLR cameras with the ability to use old optics with them, which had been manufactured for decades and often cost more than the cameras themselves.
However, there were problems with the implementation of this idea. Creating a full-size sensor was too expensive, but in a very small one there was no point.
As a result of research, a sensor was created that was one and a half times smaller than the frame of a 35-millimeter film diagonally. Thus, for such a sensor, 1.5 is its crop factor. Canon, by the way, a little later found an even more optimal solution. The crop factor of his cameras began to equal 1.6.
To somehow differ from him, Nikon began to call his crop factor DX, and a full-format FX sensor. Such an encoding continues to exist now. It is used by many other companies except Nikon.
Manufacturers of cameras with a crop factor used the fact that the area of their sensors was reduced by more than half. This allowed to save on the manufacture of powerful and expensive optics. Manufacturers began mass production of digital cameras available for a wide range of amateur photographers.