Can a full-frame image be captured with a half-frame camera at a retreat point distance?

Full frame and semi-full frame are used to describe the size of the sensor. The so-called "full" refers to the single-frame negatives of 135 camera film as a reference. The effective area of ??the photosensitive element is about 36mm × 24mm, which is called "135 full frame" (referred to as full frame or full frame); smaller than this size is non-full frame, and among non-full frame there are APS-H, APS-C, 4/3, 1 inch and other different specifications.

The photosensitive elements on mobile phones are mostly 1/2.3 inches or 1/3 inches. High-end portable cameras represented by Sony RX100 series and Canon G7X series have 1-inch specifications. Olympus, Panasonic, Yi mirrorless cameras and DJI interchangeable lens aerial drones belong to the Micro 4/3 system. Non-full-frame cameras from Nikon, Sony, Pentax, Fuji and other brands have APS-C specifications (Canon is slightly smaller than this size). Note that the 134 full frame is not the largest sensor. Larger ones include 44mm×33mm medium format (Fuji GFX, Hasselblad X1D) and 645 medium format digital backs.

One thing to emphasize here: 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 is the difference between full frame and non-full frame? In addition to size and cost, the main impacts on our actual use are as follows.

『Equivalent focal length』

Two people A and B used the same lens (such as 85/1.8) and stood in the same position to take stills of "Wu Mei Niang".

A uses a full-frame Canon 6D, and the picture captured is the "director's cut"

B uses a non-full-frame Canon 70D, and the picture captured is the "radio and television cut"

In order to facilitate comparison of the actual angle of view of lenses with different format cameras, we have introduced the concepts of "equivalent coefficient" and "equivalent focal length". For example, the equivalent focal length of the Canon 70D is 1.6x, which means that at the same distance, the 70D with a 50mm lens has basically the same angle of view as a full-frame camera with an 80mm lens.

Of course, some people say that this situation is not full-frame telephoto, but it is not rigorous. Conversely, for situations where a relatively wide viewing angle is required (such as architecture, scenery, group photos), a non-full-frame camera must be paired with a lens with a wider focal length.

『Blurring ability』

A and B are still taking pictures while standing in the same position.

A uses a full-frame Canon 6D with an 85/1.8 lens

B uses a non-full-frame Canon 70D with a 50/1.8 lens

Because we know the equivalence coefficient and equivalent focal length, so the actual picture range captured by these two combinations is basically the same (B is slightly larger).

The key to affecting the blur capability (depth of field) is the 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 A has a more obvious blur effect.

▲Portrait sample of Canon 6D

『Image quality (resolution)』

A and B are still using the 85/1.8 lens . This time, B takes a few steps back to get the same shooting angle as A.

When measuring lens resolution, we will introduce the concept of MTF (modulation transfer function). I won’t give a too in-depth explanation here. I just want to say that when measuring MTF, you need to consider the size of the camera’s sensor. To put it simply, as long as the lens is not too poor at the edges of the picture, it will perform better on a large-format camera than on a small-format camera - conversely, if a small-format camera wants to obtain the same image quality as a large-format camera, it Need a better lens.

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

『Summary』

Okay, having said so much, let us summarize.

The essential difference between full-frame and non-full-frame is the size of the sensor, which affects the cost of a camera and also largely determines the camera's size, viewing angle, blur capability and imaging quality.

In the film era, camera formats evolved from large to small. After the emergence of digital cameras, digital photosensitive elements have been subject to production processes and costs for a long time, making it difficult to produce large-size products. Based on this situation, we have reason to believe that when production technology is fully developed, the price gap between full-frame cameras and non-full-frame cameras will become smaller and smaller - in fact, today there are already many full-frame cameras that are priced lower than high-end cameras Not a full-width product.

However, the dimension of measuring a camera is not just image quality. With a limited budget, some friends will focus more on image quality, while others will focus more on shooting performance such as focusing and continuous shooting. This is also the advantage of some current high-end non-full-frame cameras over entry-level full-frame cameras. So, my view is that full-frame cameras will become more and more popular, but it’s too early to say they will replace non-full-frame cameras.