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All people who shoot, from amateurs to those who make money on it, are faced with the recalculation of the lens by crop. Only the latter perfectly understand what it is about, and they operate with this, for the rest this text is intended. It’s time to go back to basics and break down everything you need to know about the crop factor. Let’s fill the gap!
Photo: canon.com.auWhat is crop factor
Before talking about crop, it is imperative to start with the camera matrix, which is inextricably linked with it. It is located inside the carcass and is a light-sensitive sensor. For any camera, this is the most important element. From the smartphone camera, to the latest models of major brands. The camera obscura is the only option where a matrix is not needed.
In simple terms, a matrix is \u200b\u200ban analogue of photographic film. In analog cameras, the image passed through the lens and fell on the photosensitive layer of the film. In modern, digital, everything is the same, only it gets on a photosensitive matrix. It is formed there, and then saved to a memory card.
Photo: dpreview.comThe so-called full-frame (FF, Full Frame, full-frame) matrix has a size approximately equal to the size of a 35-mm film frame. Of course, this adds to the size of the camera, and the price of zeros. To reduce all these indicators (including for smartphone cameras. It is impossible to imagine a full matrix there), manufacturers have reduced this sensor.
There is an established set of such shortened matrices on the market. For example, 1.5, 1.6, 2, 4. All this is the crop factor. The number indicates how many times this matrix is smaller compared to full-frame. So, if you multiply the dimensions of the matrix with a crop of 1.5 by one and a half, then you will get the dimensions of the FF.
In everyday life, this indicator is used mainly to determine the focal length of the lens and install it on various cameras.
Chronology of the appearance of crop matrices
In analog photography, there was no such thing as crop factor. Although there was a wide range of frame window sizes on the market, each of them corresponded to a certain focal length of the lens, which was considered to be normal. For example, for large cameras with a frame size of 9x12 cm, a lens with a focal length of 135mm was standard, for a medium format 6x6 — 80mm, and for a standard one — 50mm. And on each of them, such a combination of frame size and standard lens produced more or less similar results.
Lenses with the same focal length on cameras with different frame sizes will behave completely differently. We tend to think of the 50mm as more of a portrait lens. However, on medium format it would be wide-angle. And on a large one — ultra-wide-angle. Despite such discrepancies, there was no crop in the days of analog photographic equipment: it was not necessary to recalculate the values of lenses and translate — an appropriate set of lenses was produced for each type of equipment.
There are a lot of lens adapters and cropped sensors out there now, and you have to do some calculations to figure out how a particular lens will perform on your camera.
Image: setafi.comHow crop factor works
The lens projects a round (yes, round) image straight into the body of the camera. The frame frames crop this circle to a familiar rectangle. Thus, only part of the entire image is captured. The smaller the matrix, the smaller this rectangle. Accordingly, a smaller piece of the passing image will be obtained at the output. When shooting with a cropped matrix, the camera, as it were, cuts out a rectangle 1.5 / 1.6 / 2 times smaller from a full-size frame.
Having photographed on the FF camera and cut out a rectangle 1.5/1.6/2 times smaller from the photo in the center on the computer, you will get exactly the same frame as you would get on the crop matrix.
The crop factor is how many times the sensor is reduced compared to the full frame. To understand how a lens designed for a full matrix will behave in a crop, you need to multiply the focal length by this value.
For example, in a camera with a 1.5 cropped sensor, a 50mm lens will produce an image of 50 x 1.5 = 75mm. If you screw a 75mm lens onto a film camera, you will get an image with a similar angle of view. Despite the fact that the lens on the crop is 50mm, and on ff — 75mm.
Image: picturecorrect.com 
Image: picturecorrect.com
Image: picturecorrect.comCrop vs full frame
The most popular crop factor in affordable cameras is 1.5 and 1.6. On the one hand, the larger the sensor, the higher the quality of the resulting photos. This is also affected by the quality of the lens and the level of lighting. But the fact remains, the matrix decides.
There are even medium format digital cameras, where the sensor size exceeds the standard full frame. For example, Hasselbald or the Fujifilm GFX line, where the matrix size can reach 40mm. They cost like a good car, but the images taken on them can be printed on a billboard.
The quality of a full frame is the resolution of the image, the level of detail, clarity, lack of noise in low light. If you send pictures taken under the same conditions to crop and FF for printing, then the first one will lose in all respects. In addition, a full frame is easier to crop: if during processing you often crop the frame to the required piece, then FF will not lose quality from this. Crop, on the other hand, will go strongly in pixels with a detailed approximation.
The other side of the coin is that the full frame is primarily important for those who work with the image, and the camera is a working tool for him. If you shoot for yourself and do not spend a lot of time processing, and also appreciate compact cameras, then crop is your choice. He, too, can produce a good picture that will suit your needs and request.
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