Understanding Depth of Field in Film Photography
- Michael Elliott
- 13 hours ago
- 6 min read
Depth of field is one of those concepts that sounds technical but is felt intuitively every time you look at a photograph. It is the zone of acceptable sharpness in front of and behind the point you focused on. A portrait where the background dissolves into a wash of colour has a shallow depth of field. A landscape where everything from the foreground rocks to the distant hills appears sharp has a deep one. Understanding how to control this zone is one of the most powerful creative tools available to you as a film photographer.
If you have been following the fundamentals series on this blog — covering the exposure triangle, shutter speed, and the sunny 16 rule — you already know that aperture affects exposure. What we have not yet explored is aperture's second job: governing how much of your scene falls within that zone of sharpness. This post fills that gap.

The Three Factors That Control Depth of Field
Depth of field is not controlled by aperture alone. Three variables interact: aperture, focal length, and the distance between you and your subject. Change any one of them and the depth of field shifts. Understanding the interplay is what separates a photographer who gets lucky from one who gets the result they intended.
Aperture: The Primary Control
A wider aperture — a lower f-number like f/1.4 or f/2 — produces a shallower depth of field. A narrower aperture — a higher f-number like f/11 or f/16 — produces a deeper one. This is the lever most photographers reach for first, and for good reason: it is the most immediately controllable variable without changing your position or your lens.
On a 50mm lens, the difference between f/2 and f/8 is dramatic. At f/2, focusing on someone's eyes might leave their ears soft. At f/8, you could have their entire face and much of the background in acceptable focus. On film, where you cannot review the image immediately, this distinction matters enormously. You are committing to a creative decision at the moment of exposure, and you will not know whether you got it right until the negatives are developed.
Focal Length: The Often Overlooked Factor
Longer focal lengths produce a shallower depth of field at the same aperture and subject distance. A 135mm lens at f/4 will render a far thinner plane of focus than a 28mm lens at f/4. This is why portrait photographers gravitate toward 85mm and longer lenses — the compression and shallow focus isolation they provide is difficult to replicate with wider glass.
For film photographers shooting medium format, this effect is amplified. The Pentax 67's 105mm f/2.4 standard lens behaves like a short telephoto with a depth of field so thin at wide apertures that precise focusing becomes critical. The larger negative requires longer focal lengths for equivalent fields of view, and those longer focal lengths bring shallower depth of field along for the ride.

Subject Distance: The Forgotten Variable
The closer you are to your subject, the shallower the depth of field becomes. This is why macro photography is so challenging — at very close focusing distances, even f/16 yields only millimetres of sharpness. Conversely, when you focus on something far away, depth of field extends considerably. This is the principle behind hyperfocal distance, which we will return to shortly.
Reading the Depth of Field Scale on Your Lens
One of the advantages of shooting with older manual focus lenses is that most of them have a depth of field scale engraved on the barrel. This is a set of paired f-stop markings on either side of the focus index line. If you set your lens to f/8 and focus at 3 metres, the depth of field scale shows you the near and far limits of acceptable sharpness at that aperture.
Modern autofocus lenses have largely abandoned this feature, which is a loss. The depth of field scale lets you pre-visualise your image before you press the shutter. It is an especially useful tool for street photography, where you can set a zone of focus in advance and shoot without needing to focus for each frame — a technique sometimes called zone focusing.

Hyperfocal Distance: Maximising Sharpness
The hyperfocal distance is the focus distance at which depth of field extends from half that distance to infinity. If you want maximum sharpness across an entire landscape scene, this is the technique to use. For a 50mm lens at f/11 on 35mm film, the hyperfocal distance is roughly 7 metres. Focus at 7 metres and everything from about 3.5 metres to infinity will be in acceptable focus.
You can calculate hyperfocal distance using apps or charts, but the depth of field scale on your lens provides a quick visual method. Simply align the infinity mark on the focus ring with the f-stop marking for your chosen aperture on the depth of field scale. The focus index line will then point to the hyperfocal distance, and the opposite f-stop marking shows you the near limit of sharpness.

Depth of Field as a Creative Choice
It is tempting to treat depth of field as a purely technical matter, but it is fundamentally a creative one. A shallow depth of field directs the viewer's attention. It says: look here, not there. It isolates a subject from its environment. A deep depth of field does the opposite — it invites the viewer to explore the entire frame, to find relationships between foreground and background, to take their time.
Neither approach is inherently better. The question is always: what does this image need? A street scene might benefit from deep focus that places the subject in context. A portrait might demand shallow focus that removes a distracting background. The discipline of film — where each frame costs money and time — forces you to make this decision deliberately rather than spraying frames and deciding later.
Film Format and Depth of Field
Film format has a significant effect on depth of field that is worth understanding. Larger formats require longer focal lengths to achieve the same field of view, and as we established, longer focal lengths produce shallower depth of field. A 50mm lens on 35mm film gives a standard field of view. To get the same view on 6x7 medium format, you need roughly 105mm. To get it on 4x5 large format, you need around 150mm.
This means that achieving deep focus on larger formats requires stopping down further than you would on 35mm. Large format photographers routinely shoot at f/32 or f/45 to get adequate depth of field for landscapes. Medium format photographers find themselves using f/8 or f/11 where a 35mm shooter might use f/5.6. If you are new to film and still deciding which format suits your work, the beginner's guide to film photography covers the fundamentals of choosing a camera and format.
Practical Exercises
Load a roll of film and shoot the same subject at f/2, f/5.6, and f/11 without moving your position. When you get the negatives back, compare the results. Notice not just how much is in focus, but how the images feel different. The f/2 frame will have a sense of intimacy and immediacy. The f/11 frame will feel more documentary, more contextual. Neither is wrong — they are different tools for different purposes.
Then try the hyperfocal distance technique on a landscape scene. Set your lens to a moderate aperture, use the depth of field scale to find the hyperfocal distance, and see how much of the scene you can render sharp from near to far. This is one of those techniques that sounds abstract until you see it on a negative, and then it becomes indispensable.
Depth of field is where the technical and the creative meet. Once you understand the three variables that control it — aperture, focal length, and subject distance — you stop leaving it to chance and start making it a deliberate part of your image-making. And on film, where every frame is a commitment, that deliberateness matters more than ever.