It is assumed that the whole frame and the half frame both shoot the same picture with 50 1.4. Whose depth of field is shallower?

The whole picture is relatively light. This is a fact that all photographers know.

The above answer is wrong. Don't be misled. Let me explain.

First of all, it is true that half-width changes the field of vision. 50 mm will become more than 70 mm and less than 80. But the reason for the change of sight distance here is that the half machine only uses the center of the whole lens, and the surrounding circles are not used, so according to this standard, the depth of field cannot be calculated as the above answer. That is to say, if your subject is at a distance of 1.3 meters, the size and depth of field of the full-set and half-set images are actually the same, but the half frame is small, so you can only get the middle part of the whole image. This is why half a picture needs a scaling factor to be equal to the whole picture. At this time, if you want a photo with the same size as the whole frame, you must keep a distance from the subject, which will deepen the depth of field, so that Quan Huafu will get a shallower depth of field when you get the same frame. I wonder if you can understand this.

If you follow the test upstairs, you can't get half a shallower result. You can test it yourself.