Circle of Confusion Calculator
The circle of confusion for a sensor, by the diagonal rule or from the print size and how sharp you want the print to look.
Results
Circle of confusion by that rule
0.02884
mm
Sensor diagonal
43.2666
mm
Print diagonal
325.15
mm
Enlargement from sensor to print
7.5151
Circle of confusion from the print
0.02661
mm
Crop factor
1.0000
Sensor aspect ratio
1.5000
Line pairs it resolves
34.67
lp/mm
What this tool does
Depth of field is not a property of a lens — it is a decision about how blurred a point is allowed to be before you call it unsharp. That allowance is the circle of confusion, and every depth-of-field number depends on it. Two ways of choosing it are shown here: the usual diagonal-over-1500 convention, and the honest one, which starts from the print you are going to make and how close you will stand to it.
Formula
CoC = sensor diagonal ÷ divisor · enlargement = print diagonal ÷ sensor diagonal · CoC = CoC on the print ÷ enlargement
Variables
| Symbol | Meaning | Unit |
|---|---|---|
sw | Sensor width | mm |
sh | Sensor height | mm |
dv | Which divisor rule | — |
pw | Print width | cm |
ph | Print height | cm |
cp | Blur you accept on the print | mm |
CC | Circle of confusion by that rule | mm |
SD | Sensor diagonal | mm |
PD | Print diagonal | mm |
EN | Enlargement from sensor to print | — |
CB | Circle of confusion from the print | mm |
CF | Crop factor | — |
AR | Sensor aspect ratio | — |
LP | Line pairs it resolves | lp/mm |
Worked example
- Sensor width36 mm
- Sensor height24 mm
- Which divisor rule1500
- Print width25.4 cm
- Print height20.3 cm
- Blur you accept on the print0.2 mm
- Circle of confusion by that rule0.02884 mm
- Sensor diagonal43.2666 mm
- Print diagonal325.15 mm
- Enlargement from sensor to print7.5151
- Circle of confusion from the print0.02661 mm
- Crop factor1.0000
- Sensor aspect ratio1.5000
- Line pairs it resolves34.67 lp/mm
Limitations
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.
- The calculation runs at full precision and only the display is rounded. If you copy an intermediate value and retype it, small differences can appear.