In this simple exercise, I was asked to show how a photograph of the same subject appears while changing the focus from the front to the back of it. For this, I chose water jets and selected a short telephoto lens so as to obtain a shallow depth of field and a large aperture. Thanks to a high shutter speed (1/2000th second), the water appears frozen like ice.
In the first successful attempt, the background does not look nice at all. While I attempted to frame in a way that would avoid some of the structure of the building in the background, this was limited by the need to keep the water jets in relative alignment. I made a second series, with not much improvement in the quality of the background. This time, I aimed at the water jets from a different angle, making it easier to adjust the focus.
Looking at both series, I find that the only photograph that is easy to read is the first one. The two or three front jets, looking frozen in the air, develop interesting shapes. As soon as the focus changes backwards, the prominent blurred front jets introduce some confusion. Then the eye has to search for something to rest on. To experience this, I advise you to enlarge each photograph.
I made another attempt through the window of a restaurant looking onto the street. I chose three focus points: the window, the other side of the street and the pavement nearest to me.
It is interesting to see that the writing on the window is barely noticeable on the second photograph. Indeed, choosing the right aperture and lens allows to shoot through a fence or a window while avoiding disturbing foreground elements, although the sharpness of the resulting image may suffer to a certain extent. Reviewing past photographs, I found the following examples when I used this technique.
Through the glass of an aquarium in Basel zoo: the surface of the glass was full of scratches and fingerprints.
An orangutan seen through the wires of its enclosure (although the fencing is still a bit too visible).The background can also introduce distraction to the reading of an image. In this example of a heron, I chose the aperture so as the bird stands out against a blurred background, which could otherwise appeared more cluttered.The same idea was used to avoid ungracious background for the portrait of this monkey: