Numerical aperture to equivalent f-number
Type a value in NA to get it in f/N instantly.
0.7692f/N
That's about the same as a 40× objective. It can separate detail down to about 423.1 nm.
What it means
How fine can it see?
Resolution figures use green light at 550 nm and the Abbe limit. Shorter wavelengths resolve finer, which is why electron microscopes exist.
The math
How to convert NA to f/N
Resolution and aperture are reciprocals through the wavelength: resolution = λ ÷ 2NA, which at 550 nm is 275 ÷ NA nanometers. The collection angle is arcsin(NA).
Example: 0.65 NA = 0.769231 f/N.
Every unit
Your aperture in every unit
Tables
NA to f/N conversion table
| NA | f/N |
|---|---|
| 0.04 NA | 12.5 f/N |
| 0.1 NA | 5 f/N |
| 0.25 NA | 2 f/N |
| 0.4 NA | 1.25 f/N |
| 0.65 NA | 0.769231 f/N |
| 0.75 NA | 0.666667 f/N |
| 0.85 NA | 0.588235 f/N |
| 0.95 NA | 0.526316 f/N |
| 1.25 NA | 0.4 f/N |
| 1.4 NA | 0.357143 f/N |
f/N to NA conversion table
| f/N | NA |
|---|---|
| 0.357 f/N | 1.40056 NA |
| 0.4 f/N | 1.25 NA |
| 0.526 f/N | 0.95057 NA |
| 0.588 f/N | 0.85034 NA |
| 0.667 f/N | 0.749625 NA |
| 0.769 f/N | 0.650195 NA |
| 1.25 f/N | 0.4 NA |
| 2 f/N | 0.25 NA |
| 5 f/N | 0.1 NA |
| 12.5 f/N | 0.04 NA |
Quick answers
Quick answers
- How many f/N is 1 NA?
- 1 NA is 0.5 f/N.
- How many f/N is 10 NA?
- 10 NA is 0.05 f/N.
- How many f/N is 0.65 NA?
- 0.65 NA is 0.769231 f/N.
The units
About these units
Numerical aperture (NA)
The sine of the collection half-angle, times the refractive index.
Equivalent f-number (f/N)
The camera lens aperture that gathers the same cone.
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