85mm f/1.4 3.00 m
photo: Supanut Arunoprayote / Wikimedia CommonsSubject 3.00 mBackground 40.0 m
0.3
1
2
5
10
30
100
∞
In-focus depth
9.8 cm
2.95 m – 3.05 m
in front 4.8 cmbehind 5.0 cm
Background blur
A point in the background lands on the sensor as a disc rather than a point. Its diameter b is shown as a share of the sensor width, which keeps the number comparable across formats.
Thin-lens blur disc
b = (f² / N) · (D − s) / (D · (s − f))
With your settings
b = (85² / 1.4) · (40000 − 3000) / (40000 · (3000 − 85)) = 1.64 mm
As a share of sensor width
1.64 / 36 × 100 = 4.5%
f: focal length · N: f-stop · s: subject distance · D: background distance (all in mm)
4.5%
1.64 mm
Strong
Hyperfocal
179 m
focus here → sharp to ∞
Circle of confusion
0.0288
mm