The depth of field is the range that is in focus. The smaller the aperture, the deeper the depth of field.
The depth of field is the range in front of and behind the subject that is in focus. The depth of field is greatly changed in accordance with various conditions that include the lens' focal length, aperture setting, position in focus, photographing distance, and the difference in distance between the main subject and the background.

Photo 5 shows that under the same shooting conditions, the smaller the aperture is made, the wider the depth of field becomes. In addition, the range in focus is a ratio of approximately 1:2 with the range being shallower in front and deeper behind the actual focusing distance.

Further, the "blurring" of the area away from the depth of field produces different photographic effects depending on the lens that is used, so it is important to use this effect skillfully to produce works that have a sense of perspective.