Unlike wide angle lenses, where a small difference in focal length can make a large difference in angle of view, for telephoto lenses the opposite is the case.
Jumps of 100mm or more in focal length deliver relatively small changes in angle of view, as illustrated in the table below, which compares ‘full frame’ sensors with the APS-C sized sensors used by Nikon, Pentax and Sony (a) and Canon (b) and Micro Four Thirds (M4/3) sensors (c).
| Focal length | Diagonal angle of view at infinity with different sensor sizes |
|||
| 36 x 24mm | 23.5 x 15.7mm (a) | 22.3 x 14.9mm (b) | 17.3 x 13.0mm (c) | |
| 200mm | 10 degrees | 8.1 degrees | 7.7 degrees | 6.2 degrees |
| 300mm | 6.9 degrees | 5.4 degrees | 5.1 degrees | 4.1 degrees |
| 400mm | 5.2 degrees | 4.0 degrees | 3.8 degrees | 3.1 degrees* |
| 500mm | 4.1 degrees | 3.2 degrees | 3.1 degrees | 2.5 degrees* |
| 600mm | 3.4 degrees | 2.7 degrees | 2.6 degrees | 2.1 degrees* |
| 800mm | 2.6 degrees | 2.0 degrees | 1.9 degrees | 1.5 degrees* |
While DSLR cameras with APS-C sized sensors can normally use lenses designed for ‘full frame’ cameras, the longest focal length available for cameras with 17.3 x 13.0mm sensors is currently 300mm. However, longer lenses can be attached to some M4/3 cameras via adaptors, so we have included the angle of view coverage figures for longer lenses, but marked them with an asterisk (*).
