Source from: aperture
The amount of light captured by a lens is proportional to the area of the aperture, equal to:
Where f is focal length and N is the f-number.
Here, the focal length is 50mm:
| D (mm) | R (mm) | Area (mm²) | f/ stops |
| 41,7 | 20,8 | 1363,5 | 1,2 |
| 35,7 | 17,9 | 1001,8 | 1,4 |
| 27,8 | 13,9 | 606,0 | 1,8 |
| 25,0 | 12,5 | 490,9 | 2 |
| 17,9 | 8,9 | 250,4 | 2,8 |
| 12,5 | 6,3 | 122,7 | 4 |
| 8,9 | 4,5 | 62,6 | 5,6 |
| 6,3 | 3,1 | 30,7 | 8 |
| 4,5 | 2,3 | 16,2 | 11 |
| 3,1 | 1,6 | 7,7 | 16 |
| 2,3 | 1,1 | 4,1 | 22 |
