When taking a picture with two objects at the same time, how does the camera focus then?

If it's a DSLR there is a depth of field mode that will focus 2 times and then automatically give you the exposure data. The practical application is to take the middle point of the 2 objects to focus, and control the depth of field by contracting the aperture. It's generally best to half-press the shutter to focus and then recompose the picture, so that it generally does not run out of focus.

Adjusting the focus, changing the posture, looking for the angle, the damn can't get the right focus to shoot the desired effect! Soft fast cramp fingers, but there is nothing to be done. Nowadays, the autofocus function of DSLR camera is very powerful, so my friends are used to autofocus, in fact, in the dark light conditions or the subject contrast is small, manual focus is more convenient and operable.

Expanded information;

Traditional cameras, take a similar way to visual distance measurement to achieve autofocus, the camera emits a kind of infrared (or other rays), according to the subject's reflection to determine the distance of the subject, and then according to the results of the measurement of adjusting the lens combination, to realize the autofocus.

This autofocus method - direct, fast, easy to realize, low cost, but sometimes wrong (between the camera and the subject there are other things such as glass can not be realized when the autofocus, or in the case of insufficient light), the accuracy is also poor, today's high-grade cameras have generally not used this method.

Because the camera actively emits rays, it is called active, and because it is actually only measuring the distance, and not through the actual image of the lens to determine whether it is correctly focused, so it is also known as non-TTL type.

Baidu Encyclopedia-Focusing