Depth of Field Explained: Aperture, Focal Length, Distance and Hyperfocal

What Is Depth of Field?

When you focus on a subject, only one distance is perfectly sharp. Just in front of and behind it, the blur is so small that the eye doesn't notice it. This zone of acceptable sharpness is the depth of field (DoF).

• Shallow depth of field: the subject is sharp, the background melts into a soft blur — the classic portrait look.
• Deep depth of field: everything is sharp from the foreground to the horizon — the classic landscape look.

Mastering it is one of the first steps from "taking pictures" to "making photographs".

The Three Settings That Control It

Setting	Shallower depth (blurry background)	Deeper depth (everything sharp)
Aperture	Wide: f/1.4, f/1.8, f/2.8	Narrow: f/8, f/11, f/16
Focus distance	Subject close to the camera	Subject far away
Focal length (same position)	Long: 85 mm, 135 mm	Short: 16 mm, 24 mm

The distance between subject and background also plays a huge role in how blurry the background looks: a subject 1 m from a wall gives little blur; the same subject 10 m in front of trees gives a lot.

Calculate Your Depth of Field

The depth of field calculator computes, for your camera and lens:

• the near and far limits of the sharp zone,
• the hyperfocal distance,
• the size of the background blur,
• the framing (what fits in the picture at that distance),
• the full-frame equivalents of your focal length and aperture.

A live preview shows a scene at real sizes and distances, with each plane blurred according to your settings. The Share button copies a link that reopens the calculator with the same camera, lens and settings — handy on a forum or in a shooting brief.

The Circle of Confusion

Depth of field calculations rely on a threshold: the circle of confusion, the largest blur spot still perceived as a point. The standard is the sensor diagonal divided by 1442:

Sensor	Circle of confusion
Full frame (36 × 24 mm)	0.030 mm
APS-C	~0.020 mm
Micro Four Thirds	0.015 mm

This standard corresponds to a print viewed at a normal distance. If you inspect your images at 100% on a screen, the truly sharp zone is shallower than the calculation says.

Hyperfocal Distance: the Landscape Technique

The hyperfocal distance is the closest focus distance at which everything up to infinity stays acceptably sharp. Focus there, and the sharp zone runs from half that distance to the horizon.

Examples on full frame:

Lens	Aperture	Hyperfocal	Sharp from
24 mm	f/8	~2.4 m	~1.2 m to infinity
35 mm	f/8	~5.1 m	~2.6 m to infinity
50 mm	f/11	~7.6 m	~3.8 m to infinity

In the calculator, the "Focus at hyperfocal" button sets it in one click.

The 1/3 – 2/3 Rule

Sharpness extends further behind the focus point than in front of it. At a few meters, about a third of the zone is in front and two thirds behind. In macro photography, it's close to half and half. Practical consequence: in a group photo, focus on the first third of the rows, not on the back.

Practical Recipes

• Portrait with blurry background: 85 mm, f/1.8–f/2.8, subject at 2–3 m, background as far as possible.
• Group of people: 35 mm, f/5.6–f/8, focus on the second row.
• Landscape: 16–24 mm, f/8–f/11, focus at the hyperfocal distance.
• Macro: f/8–f/16 (depth is tiny, often a few millimeters), or focus stacking.
• Street photography: 28–35 mm at f/8, pre-focused at 3 m ("zone focusing").

Want to know what settings were used for a photo you like? Its EXIF data often contains the aperture, focal length and camera — read them with the EXIF viewer.

Conclusion

Depth of field comes down to three settings — aperture, distance, focal length — plus sensor size. Open wide and get close to isolate a subject; close down and use the hyperfocal distance to get everything sharp. And when in doubt, calculate before shooting.