DB Labs
What Is Depth of Field?
Depth of field is the distance between the nearest and farthest objects in a scene that appear acceptably sharp in a photograph. A shallow depth of field has a thin in-focus slice with everything in front and behind blurred — the classic "Portrait mode" look. A deep depth of field keeps most of the scene sharp from foreground to background.
What Controls Depth of Field
- Aperture: Wider apertures (smaller f-numbers like f/1.4) produce shallower depth of field. Narrower apertures (f/8, f/16) produce deeper depth of field.
- Focal length: Longer lenses (telephoto) produce shallower depth of field than wider lenses at the same aperture.
- Distance to subject: The closer you focus, the shallower the depth of field. Macro photography has extremely shallow depth of field.
- Sensor size: Larger sensors (full-frame) produce shallower depth of field than smaller sensors (smartphone) at equivalent settings.
Why iPhone Can't Match Big Cameras Optically
iPhone's small sensor and tiny lens physically cannot produce the same shallow depth of field as a DSLR or mirrorless camera with a 50mm f/1.4 prime. The depth of field on a phone-sized lens is naturally very deep, meaning everything tends to look sharp regardless of distance. To get the look of professional portraits, Apple developed Portrait mode.
How Portrait Mode Fakes Shallow Depth
Portrait mode on iPhone (introduced with iPhone 7 Plus in 2016) uses a combination of machine learning, depth data from the camera system, and computational processing to create a depth map of the scene. iOS then identifies the subject (person, pet, object) and digitally blurs everything else proportionally to its distance from the focus point. The result is a "fake" shallow depth of field that approximates the optical look of a much larger camera.
iPhone 15 and later can capture depth information in any photo by default and convert it to Portrait mode after the fact — you no longer have to switch to Portrait mode before taking the shot.
Bokeh
Bokeh is the visual quality of out-of-focus areas in a photograph, often appearing as soft circular highlights from light sources. iPhone Portrait mode includes a Studio Light effect and adjustable f-stop slider (f/1.4 to f/16) that controls the amount of simulated bokeh after the photo is taken.
Related Terms
Frequently Asked Questions
What is depth of field in photography?
The range of distance in a photo where objects appear sharp. Shallow has a thin in-focus zone; deep keeps most of the scene sharp.
How does iPhone create shallow depth of field?
Portrait mode uses depth sensors and machine learning to identify the subject and digitally blur the background.
What controls depth of field on a real camera?
Aperture, focal length, distance to subject, and sensor size all affect depth of field.
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