How do I get maximum background blur?

Use the widest aperture, longest focal length, shortest subject distance, and maximum subject-to-background distance. An 85mm f/1.2 with subject at 2m and background at 20m produces extreme blur. Each factor contributes independently.

Does the background distance matter for blur?

Yes, significantly. Background objects further from the focal plane are more blurred. A background at 5m (2.5m behind a 2.5m subject) is far less blurred than a background at 20m. Choosing locations with distant backgrounds dramatically improves portrait blur.

How does entrance pupil relate to blur?

The entrance pupil (focal length / f-number) is the physical diameter of the lens opening. A larger entrance pupil creates more blur. An 85mm f/1.4 has a 60.7mm entrance pupil. A 200mm f/2.8 has a 71.4mm entrance pupil — more blur despite being 2 stops slower.

What is the best portrait lens for blur?

On full frame: 85mm f/1.2-1.4, 105mm f/1.4, 135mm f/1.8, or 200mm f/2.0 produce outstanding background blur. Budget options: 85mm f/1.8 or 50mm f/1.4. The 135mm f/1.8 offers an excellent balance of blur, working distance and compression.

PhotoCalcs

Background Blur Calculator — Portrait Background Blur

Calculate the amount of background blur for portraits based on lens settings and distances.

Focal Length

Focal length of the lens in millimetres

Aperture

Lens aperture (f-stop number)

Subject Distance

Distance from camera to subject

Background Distance

Distance from camera to the background you want blurred

How We Calculate This

Background Blur Disc

d = (f × D × |b − s|) / (b × (s − f))

Where D = f/N (entrance pupil diameter), f = focal length, s = subject distance, b = background distance. The result is the diameter of a background point's blur disc projected onto the sensor.

Key Insight

Blur increases with entrance pupil size and subject-to-background distance. As the background moves farther away the blur disc increases, rising toward the limit f × D / (s − f) as background distance approaches infinity.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates based on standard optical and photographic formulas. Results may vary with specific equipment.