Normal lens facts for kids
A normal lens is a special kind of camera lens. It helps your photos look very natural. When you take a picture with a normal lens, everything in the photo appears similar to how your own eyes see the world.
This happens because of something called the lens's focal length. The focal length is like the "strength" of the lens. For a normal lens, this strength is usually about the same as the diagonal measurement of the film or digital sensor inside the camera.
If a lens has a shorter focal length than a normal lens, it's called a wide-angle lens. These lenses make things look further away and fit more into the picture. If a lens has a longer focal length, it's called a telephoto lens. These lenses make distant things look closer, like a telescope.
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Normal Lenses for Film Cameras
Different types of film cameras use different sizes of film. Because of this, the "normal" focal length changes for each film size. The table below shows some common film sizes and the focal length that gives a natural view.
| 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 |
Normal Lenses for Digital Cameras
In digital photography, cameras use electronic sensors instead of film. Just like with film, the size of the sensor affects what focal length is considered "normal." Many digital cameras today have zoom lenses, which means their focal length can change. The table below shows typical normal focal lengths for different digital sensor sizes.
- The "TV-tube diameter" column refers to old television screen sizes. This was a way to measure sensor size in the past.
- The "Normal lens focal length" for many modern digital cameras is often a calculation, as most cameras use zoom lenses that cover many focal lengths.
| 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 |
Normal Lenses in Movies
In cinematography (making movies), the idea of a "normal" lens is a bit different. For movies, a focal length that is about twice the diagonal of the film frame is often considered normal. This helps create a natural look for the big screen.
| 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
In Spanish: Objetivo normal para niños
