Can a half-frame camera take a picture of Quan Huafu at a certain distance from the back point?

Quan Huafu and full width at half maximum are used to describe the size of photosensitive elements. The so-called "full" is a single negative based on 135 camera film. The effective area of photosensitive element is about 36mm×24mm, which is called "135 Quan Huafu" (abbreviated as Quan Huafu or full width). Smaller than this size is the incomplete width, which has different specifications such as APS-H, APS-C, 4/3, 1 inch.

Most of the photosensitive elements on mobile phones are 1/2.3 inches or 1/3 inches. The high-end portable cameras represented by Sony RX 100 series and Canon G7X series are 1 inch. Olympus, Panasonic, ant micro camera and DJI interchangeable lens aerial drone all belong to micro 4/3 system. Nikon, Sony, Pentax, Fuji and other brands of non-full-frame cameras are APS-C specifications (Canon is slightly smaller than this size). Note that 134 Quan Huafu is not the largest photosensitive element, and there are 44mm×33mm medium format (Fuji GFX, Hasselblad X 1D) and 645 medium format digital backs larger than it.

It should be emphasized here that xx inches represents the diagonal length of the photosensitive element. For historical reasons, 1 inch here is 16mm instead of the normal 25.4mm..

So what's the difference between Quan Huafu and non-full-width? In addition to size and cost, the impact on our actual use mainly includes the following aspects.

equivalent focal length

A and B use the same lens (for example, 85/ 1.8) and stand in the same position to shoot Wu Meiniang's stills.

A uses Quan Huafu Canon 6D, and the picture taken is "Director's Cut Edition".

B Using a Canon 70D that is not full-size, the picture taken is a "radio and television editing version".

In order to compare the actual viewing angles of lenses under different frames, we introduce the concepts of "equivalent coefficient" and "equivalent focal length". For example, the equivalent focal length of Canon 70D is 1.6x, which means that at the same distance, the viewing angles of 70D with 50mm lens and full-frame camera with 80mm lens are basically the same.

Of course, some people say that this situation is not fully profitable, but it is not rigorous. On the other hand, for occasions that need large-angle shooting (such as buildings, landscapes and group photos), non-full-frame cameras must be matched with lenses with wider focal lengths.

"fuzzy ability"

Or a and b, stand in the same position and shoot.

Quan Huafu Canon 6D, 85/ 1.8 lens.

B Canon 70D with a 50/ 1.8 lens.

Because we know the equivalent coefficient and the equivalent focal length, the actual range of photos taken by these two combinations is basically the same (B is slightly larger).

The key factors affecting blur ability (depth of field) are shooting distance, physical focal length and lens aperture. A and B have the same shooting distance and the same aperture size. The only difference is the focal length. The larger the physical focal length, the stronger the blur effect, so the final photo is A, and the blur effect is more obvious.

▲ Canon 6D portrait proofs

"Imaging quality (resolution)"

Still A and B, also use 85/ 1.8 lens. This time, B stepped back and got the same shooting angle as A. ..

When measuring lens resolution, we will introduce the concept of MTF (modulation transfer function). I won't explain it too deeply here, but I just want to say that the size of the camera's photosensitive element should be considered when measuring MTF. Simply put, as long as it is not a lens with bad edges, it will perform better on a large-format camera than a small-format camera-conversely, a small-format camera must be matched with a better lens if it wants to obtain the same image quality as a large-format camera.

This inference is actually very important because it is directly related to the overall cost of configuring the camera.

"Summary"

Well, having said that, let's sum up. The essential difference between Quan Huafu and non-Quan Huafu lies in the size of the photosensitive element, which affects the cost of a camera, and also largely determines the camera's volume, viewing angle, blur ability and imaging quality.

In the movie era, the camera frame changed from big to small. However, after the appearance of digital cameras, digital photosensitive elements were restricted by production technology and cost for a long time in the past, and it was difficult to make large-size products. Based on this situation, we have reason to believe that the price gap between full-frame cameras and non-full-frame cameras will become smaller and smaller when the production technology is fully developed-in fact, many full-frame cameras are now lower than high-end non-Quan Huafu products.

However, measuring the size of a camera is not just about image quality. With limited budget, some friends will pay more attention to image quality, while others will pay more attention to shooting performance such as focusing and continuous shooting, which is the advantage of some high-end non-full-frame cameras over entry-level full-frame cameras. So my opinion is that full-frame cameras will become more and more popular, but it is still too early to replace non-full-frame cameras.