Normal lens Lens
In photography and cinematography a normal lens is a lens that generates images that are generally held to have a “natural” perspective similar to human eyesight, compared with lenses with longer or shorter focal lengths.
Lenses of shorter focal length are called wide-angle lenses, while longer focal length lenses are called telephoto lenses.
In still photography, a normal lens is a lens whose focal length is roughly equivalent to the diagonal of the image projected within the camera.
- Standard normal lenses for various film formats for photography are:
| Film format | Image dimensions | Image diagonal | Normal lens focal length |
|---|---|---|---|
| 9.5 mm Minox | 8 × 11 mm | 13.6 mm | 15 mm |
| APS C | 16.7 × 25.1 mm | 30.15 mm | 28 mm, 35 mm |
| 135 | 24 × 36 mm | 43.27 mm | 50 mm, 45 mm |
| 120/220, 6 × 4.5 (645) | 56 × 45 mm | 71.84 mm | 75 mm |
| 120/220, 6 × 6 | 56 × 56 mm | 79.20 mm | 80 mm |
| 120/220, 6 × 7 | 56 × 68 mm | 88.09 mm | 90 mm |
| 120/220, 6 × 9 | 56 × 84 mm | 100.96 mm | 105 mm |
| large format 4 × 5 sheet film | 96 × 120 mm (image area) | 153.67 mm | 150 mm |
| large format 8 × 10 sheet film | 194 × 245 mm (image area) | 312.51 mm | 300 mm |
For a 35 mm camera with a diagonal of 43 mm, the most commonly used normal lens is 50 mm, but focal lengths between about 40 and 58 mm are also considered normal.
The 50 mm focal length was chosen by Oskar Barnack, the creator of the Leica camera, as a compromise between the theoretical value and good sharpness, as lens technology at the time was such that slightly longer focal lengths were able to achieve optimum sharpness.
- In Digital photography the situation is more complex. The sensor type diameter is not the sensor diameter:
- (*) refers to tv-tube diameters that were standards in the 50’s. The normal lens focal length is roughly 2/3 of the TV tube diameter.
- (**) this is a mathematical calculation because most of the cameras are equipped with zoom lenses.
| Sensor type | TV-tube diameter * | Image dimensions | Image diagonal | Normal lens focal length ** |
|---|---|---|---|---|
| 1/3.6″ | 7.1 mm | 4.00 x 3.00 mm | 5.00 mm | 5 mm |
| 1/3.2″ | 7.9 mm | 4.54 x 3.42 mm | 5.68 mm | 5.7 mm |
| 1/3″ | 8.5 mm | 4.80 x 3.60 mm | 6.00 mm | 6 mm |
| 1/2.7″ | 9.4 mm | 5.37 x 4.04 mm | 6.72 mm | 6.7 mm |
| 1/2.5″ | 10.2 mm | 5.76 x 4.29 mm | 7.2 mm | 7 mm |
| 1/2″ | 12.7 mm | 6.40 x 4.80 mm | 8.00 mm | 8 mm |
| 1/1.8″ | 14.1 mm | 7.18 x 5.32 mm | 8.93 mm | 9 mm |
| 1/1.7″ | 14.9 mm | 7.60 x 5.70 mm | 9.50 mm | 9.5 mm |
| 1/1.6″ | 15.9 mm | 10.5 mm | ||
| 2/3″ | 16.9 mm | 8.80 x 6.60 mm | 11.00 mm | 11 mm |
| 1″ | 25.4 mm | 12.80 x 9.60 mm | 16.00 mm | 16 mm |
| 4/3″ | 33.9 mm | 18.00 x 13.50 mm | 22.50 mm | 23 mm |
| (APS-C) 1/8″ | 45.7 mm | 22.70 x 15.10 mm | 27.3 mm | 27 mm |
| DX | n/a | 23.7 x 15.8 | 28.40 mm | 28 mm |
| FF (35 mm film) | n/a | 36 x 24 mm | 43.30 mm | 50 mm |
| (4 x 5 cm) | n/a | 49.0 x 36.7 mm | 61.22 mm |
- In cinematography a focal length roughly equivalent to twice the diagonal of the image projected within the camera is considered normal.
| Film format | Image dimensions | Image diagonal | Normal lens focal length |
|---|---|---|---|
| N-8 | 3.68 x 4.88 mm | 6.11 mm | 12 - 15 mm |
| Single - 8 (FUJI) | 4.22 x 6.24 mm | 7.53 mm | 15 - 17 mm |
| Super - 8 | 4.22 x 6.24 mm | 7.53 mm | 15 - 17 mm |
| 9.5 mm | 6.5 x 8.5 mm | 10.70 mm | 20 mm |
| 16 mm, magnetical sound | 7.49 x 10.26 mm | 12.70 mm | 25 mm |
| 16 mm, optical sound | |||
| 35 mm | 18.00 x 24.00 mm | 30.00 mm | 60 mm |
| 35 mm, sound | 16.03 x 22.05 mm | 40.53 mm | |
| 65 mm | |||
| 70 mm | 52.6 x 23.0 mm | 57.41 mm |
See also
- angle of view
- photographic lens
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