Aperture vs Distance: What Affects Depth of Field More?
Which matters more for depth of field, aperture or distance? The honest answer is that it depends on what you hold constant, and once you see why, the question changes. Start with the rule that governs all of it: depth of field grows in proportion to the f-number, grows with the square of the distance to the subject, and shrinks with the square of the focal length.
The scaling rule in numbers
Doubling the f-number (two stops) doubles the depth of field. Doubling the distance roughly quadruples it. Doubling the focal length cuts it to a quarter. Here is one lens, a 50 mm at f/2.8 with the subject 3 m away on full frame, which has a zone about 58 cm deep, changed one thing at a time:
| What changes | Zone in focus |
|---|---|
| Aperture f/1.4 | 29 cm |
| Aperture f/5.6 | 1.2 m |
| Aperture f/11 | 2.6 m |
| Aperture f/16 | 4.7 m |
| Distance 1 m | 6 cm |
| Distance 1.5 m | 14 cm |
| Distance 6 m | 2.4 m |
| Distance 12 m | 10.9 m |
| Focal length 25 mm | 2.7 m |
| Focal length 35 mm | 1.2 m |
| Focal length 100 mm | 14 cm |
| Focal length 200 mm | 3.4 cm |
Per doubling, distance and focal length have the larger effect, each changing the depth by a factor of four, against two for the f-number. That is where "distance matters more than aperture" comes from. But it is only half the story.
The framing catch
Change the distance or the focal length and the picture changes, because the subject gets bigger or smaller in the frame. You rarely want that. If you change both together to keep the framing, so the subject stays the same size, the effects cancel almost exactly. With the same subject framed the same, at f/2.8 on full frame, a 25 mm lens from 1.5 m gives a zone of about 59 cm, a 50 mm from 3 m about 58 cm, a 100 mm from 6 m about 57 cm, and a 200 mm from 12 m about 57 cm. They are all the same.
That is the answer to the question. Of the three controls, aperture is the only one that changes depth of field without changing the composition. At a fixed framing, depth of field is set by the f-number and the sensor size, and nothing else. Distance and focal length matter when you let the framing change. The depth of field basics page makes the same point.
What this means for background blur
Subject depth of field and background blur are not the same thing. At a fixed framing the zone in focus stays put, but the background gets more blurred with a longer lens, because the blur on a distant background grows with focal length divided by f-number. That is covered in the bokeh guide. So for a blurrier background, the order of attack is usually this. First move the subject further from the background, which costs nothing. Then use a longer lens and step back to keep the framing. Then open the aperture, which also thins the zone in focus on your subject, so stop short of the extreme if you want both eyes sharp.
What this means for deep focus
For a landscape, the quickest gains are a wider lens and a smaller aperture, then focusing at the hyperfocal distance. Stepping back helps too, but it changes the framing, so it only helps if you can afford a smaller subject. Stopping down beyond about f/11 to f/16 starts to cost sharpness through diffraction.
At close range
At macro distances, distance dominates completely. At 1:1 and f/16, the whole zone is under 2 mm deep, and a mere shift in position changes everything. The practical answer there is to stack frames, not to stop down further.
To try any of these combinations, put them into the calculator and watch the near and far limits move.
Related reading: What is Depth of Field?, Hyperfocal Distance Explained, 7 Depth of Field Myths Debunked.