The topic of depth of field just keeps coming up and I suppose it deserves a revisit.
There must be a reason why depth of field is so elusive to so many photographers.
As I think about a recent photograph I saw I wonder if the confusion some photographers have might be because modern cameras are so jam-packed with image saving abilities like internal computers that control focus, balance the colour, and manage the exposure. Maybe… gosh, all that makes me understand why some new users believe all they need to get a good photo is move the mode selector to “P” then point and shoot with little thought to anything but how exciting it is to take the picture.
I seem to always be explaining how depth of field works to photographers that visit my shop. However, some people just give me a strained smile while nodding like they understand what I am talking about when I mention depth of field. Then at some future time when I occasionally see their photographs on Facebook I realize they actually did not understand me and might have been much happier with the conversation if I simply told them the reason their picture wasn’t sharp was because they needed a new lens. (Buying a new lens is so much easier and more exciting than taking a class or reading about photography.)
I recently viewed an image a photographer had posted online. He commented that he was proud of his creative and unusual view. I will say that he had chosen a pleasing viewpoint and the overall exposure was fairly good, the colours were close to reality, and the centre of the picture was in focus. Nevertheless, other than the small in-focus area around his main subject the rest of his picture wasn’t in focus at all.
I wondered if that blurry foreground and background was on purpose, and that’s what he meant by “creative and unusual”. I suppose it could be, but I found it distracting and have my doubts that other than his choice of subject and camera angle that little else was on purpose.
The definition of depth of field is, “that area in front of and behind the main subject that is in acceptably sharp focus”.
In application the wider the selected lens aperture the less the “depth of field” or that area of sharp focus, around the main subject will be. Practically, the field of focus will be 0ne-third in front and two-thirds behind the subject.
Using a wide aperture can increase the exposure in limited lighting conditions; but, along with the benefit of additional light reaching the camera’s sensor, the resulting effect is reduced depth of field. Creating a field of focus behind the subject of four inches or so might look really good when making a portrait of one person, but it is not always effective in a scenic or group photo.
The smaller the selected lens aperture the more the area of focus in front of and behind the subject will be. I prefer using a small aperture for scenic photography where I am concerned with all elements in the photograph front to back being sharp. Along with selecting what equipment I think is best for a photograph, I also think about the exposure, shutter speed and aperture. Do I want lots of depth of field or hardly any?
The Internet is packed with information on scenic photography, and there are thousands (millions?) of books and how-to articles on photography that are easy to read. I expect that examination on scenic photography, for example, will include a full discussion of depth of field.
Stay safe and be creative.