What makes good subject isolation?

Strong isolation requires shallow DOF (wide aperture, longer focal length, close distance) AND sufficient subject-to-background distance. A 85mm f/1.4 with 5m between subject and background gives excellent isolation. The background should be far enough to fall well outside the DOF zone.

How is the isolation score calculated?

The score combines depth of field and background blur disc size. A larger blur disc means more background blur. The score runs from 0 (no isolation) to 100 (complete background dissolution). Scores above 50 give clearly visible separation between subject and background.

Which has more impact: aperture or distance?

Subject-to-background distance often has more practical impact than aperture. An f/4 lens with 10m between subject and background can isolate better than f/1.4 with 1m separation. However, wider apertures always help — the ideal is both wide aperture and good separation.

Does focal length affect isolation?

Yes, in two ways. Longer focal lengths give shallower DOF at the same aperture and framing. They also compress perspective, making backgrounds appear larger but more blurred. For portrait isolation, 85-135mm on full frame is the classic choice.

PhotoCalcs

Subject Isolation Calculator — Background Separation

Measure how well your subject separates from the background with a combined DOF and blur analysis.

Focal Length

Aperture

Subject Distance

Background Distance

Sensor

How We Calculate This

Subject DOF

Calculated using standard thin-lens DOF equations.

Background Blur Disc

d = (f x D x |b - s|) / (b x (s - f))

Isolation Score

Based on the blur disc size relative to typical sensor dimensions. Larger blur discs indicate stronger background separation.

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.