There are at least two broad meanings of the term “focus” in relation to photography. The common one is to bring the subject into focus, to make it not-blurry. Effectively it is not the subject that is out of focus but the focal plane which is either in the wrong place and needs to be moved closer to or away from the aperture, or is not deep enough and needs to be increased by reducing the size of the aperture.

The other meaning of “focus” is slightly more interesting. Here we’re talking about the subject of the photograph, that which we want to draw attention to. There could be many identifiable things in the image but we want the viewer to ignore them and focus on one in particular. We do this in at least two ways.

The first is to use compositional techniques, such as the Rule of Thirds and creative lighting, to leverage cognitive biases in the viewer’s mind telling them what is important and what is irrelevant. We build up the image, as a painter might, to create a story which leads the viewer through the image, causing them to pause as they understand the subject through the visual cues that lead them to it.

The second is through framing. Here we decide what to include and what to leave out. Photography is in many ways a subtractive art. We create involving photos by excluding many of the things that make up reality and then asking the viewer to put them back. What happened before and after is removed as we take a slice through time. And what is happening beyond the edges of the photo is excluded, to be ignored or imagined but never known.

The edges of the photo have become interesting to me. Being in the camera obscura you have a sense that you’re seeing everything, but then someone walks in to the frame and you’re surprised. Where did they come from? There isn’t supposed to be anything beyond the edges.

This blinkered view is embedded into photography. We zoom in and crop out to focus on the subject and the resulting image is better for it. This mimics how our brain processes the surprisingly wide visual field our eyes are constantly pouring into it. We are vaguely aware of things in the periphery but we mostly ignore them, focussing on a relatively small area in the middle. We mentally zoom in and crop, so it’s no surprise our cameras are made to do this too.

Wide-angle lenses do exist, but they look wrong. The barrelling of the fisheye is the most immediate problem, but they also push the background away, creating a distancing between anything in the foreground and its context. The GoPro, frequently mounted on the subject, actually uses this to its advantage, emphasising the thrillseeker and making their context seem vast and awe-inspiring. They know it didn’t look quite like that in reality, that it looks wrong, but we on our laptops are ignorant that a trade-off has been made.

To focus is to exclude, to create voids. And in doing so it is to invite speculation and imagination, for the brain abhors a vacuum and will fill it with ideas. And that is where photography gets its power from.