Balancing Aperture and Composition in Photography
Aperture is the physical lens entry through which light passes to be recorded on the film/glass/chemical/sensor which results in an image.
A lens variable aperture will move throughout a range restricted by the maximum and minimum physical mechanical limit. The maximum aperture of a lens will be “wide open” indicated by a small number (ie f/1.4, f/2) or “closed” indicated by a larger number (ie f/16, f/22). The “f/” is a mathematical fraction, where “f” is focal length “/” divided by, and then whatever number that is. So a 50mm f/2 lens means the aperture could be written as 50÷2, although no one actually does this. The actual maths and specifics aren’t important in practice, just as you don’t need to understand petrol chemistry to be able to drive a car.
The aperture setting an image is exposed through will have an effect on the aesthetic - again in a way that can be heavily analysed and explained via maths, which I will not do here.
A wide aperture will mean narrow depth of field (a lot out of focus with one plane of focus sharp) while stopping down means deepening the depth of field (a lot in focus, many consecutive focus planes sharp).
Lower aperture lenses have the allure of being able to render images with an aspect that can be very beautiful — falloff, the way that focus is very thin, with a quality of out-of-focus area referred with with the Japanese word “bokeh” which I often jokingly pronounce like “bouquet” as in flowers.
The way I explain this while teaching is squinting the eye — when you struggle to see something, closing your eye somewhat and squinting often helps bring it into focus, as you are effectively manually “stopping down” the eye and rendering more in focus as a result.
For my photography I most commonly use lenses with the widest aperture being f/2 or f/2.8, with only a few lenses that go lower. Lower aperture lenses become very large and heavy due to the physics involved in bending light at that level. Many years ago I photographed a lot with a f/0.95 lens, which was fun, but ultimately I decided did not fit with what I was working on.
Focal length also has an effect on falloff, and combined with the consideration of aperture some lenses will simply be better suited for certain rendering “effects” than others. For a wide angle lens to have thin depth of field they need to have fairly wide apertures, while some telephoto lenses will basically never have a deep depth of field even at f/32. My 500mm f/8 has the thinnest depth of field in my current lineup, requiring a lot of attention for precision on my manual focus SLR. My 24mm f/2 has quite deep depth of field even wide open at f/2, meaning it can be used with much less precision.
28mm is a favourite focal length for many documentary and street photographers because set to f/8 with the focus manually at around 2 meters you will get basically everything in focus without needing to critically focus, leaving composition the only thing you need to actually do in the moment.
With all of that in mind, a balancing act must take place utilising the aesthetic vibe aperture/depth of field offers.
If you have very thin depth of field, background entirely bokeh-ed to oblivion and subject promenant against it then that subject has to be “perfect” while the composition itself is less important. After all, arranging things in a frame only matters when it’s not just one thing against a dreamy background.
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If you have a deep depth of field, with everything through foreground, midground, and background, then the composition has to be impeccable, far more significant than the singular highlighted subject of a bokeh-heavy shot.
For portraiture, use of thin depth of field often makes a lot of sense to accentuate the subject. For photographing scenes with a lot going using a narrow aperture and wider FOV lens will mean composing those unfolding events with great care so that the entire frame works within itself.
I’m not saying that one use of technique is easier than the other — environmental portraiture means the subject is one element among many and using a wide aperture would detract because it’s more of a scene than individual situation.
I’m explaining that in my moment to moment thinking while photographing I know what lens I am using (obviously) and what aperture I need to switch to depending on what is in front of me.
I’m making a portrait, so I open the aperture wide, and compose so that the background bokeh will be complimentary, not distracting.
I’m making an environmental portrait so I close the aperture, and compose so that the foreground, midground, and background don’t clash, or overlap in ways I dislike.
I’m capturing a specific detail, so I open the aperture to eliminate distraction as best as possible.
I’m working in a fast paced situation, so I close the aperture about midway and do my best to separate things out as best as possible.
Written out in these terms it seems awfully simple, I’m just doing exactly what I feel I need to do in order to get the best result. Of course, it is only as simple and intuitive as practice, experience, and past failures allow.
These aren’t things I always do, or things anyone “must” do to take a photo that looks like mine, or is in any way decent. They just aren’t considerations I consciously made when I first started to take photography seriously. They are now.
