Angle of view
From Free net encyclopedia
In photography, angle of view (also called angle of coverage or field of view) is the amount of a given scene shown on the film or image sensor (in analogue and digital photography, resp.); that is, there is generally much more to a scene visible to humans than shows up in photos, and various lenses record different degrees of the total image. There are also different ways to measure the angle of view:
- horizontally
- diagonally
- vertically
Angle of view is affected by choice of lens:
- wide-angle lenses get considerably wider angle of view than telephoto lenses
- with a fisheye lens recording up to 180° of a scene
- the longest lenses recording less than 2° (e.g., the Canon EF 1200mm lens has a horizontal viewing angle of 1°45′)
Longer lenses tend to magnify the subject, compressing distance and (when focused on the foreground) blurring the background because of their shallower depth of field. Wider lenses tend to magnify distance between objects while allowing greater depth of field. One result of using a wide angle lens in close proximity to the subject is an apparent perspective distortion: parallel lines may appear to converge and with a fisheye lens, straight edges will appear to bend.
Because different lenses generally require a different camera-subject distance to preserve the size of a subject, changing the angle of view can indirectly distort perspective, changing the apparent relative size of the subject and foreground.
| Image:Angleofview 28mm f4.jpg | Image:Angleofview 50mm f4.jpg |
| Image:Angleofview 70mm f4.jpg | Image:Angleofview 210mm f4.jpg |
For a non-distorting, regular (non-fisheye) lens, the angle of view (α) can be calculated from the film or sensor dimension (d), and effective focal length (f) thus:
- <math>\alpha = 2 \arctan \frac {d} {2 f}</math>
The effective focal length can be set equal to the focal length of the lens (F), except in macro photography where the magnification (m) must be taken into account:
- <math>f = F \cdot ( 1 + m )</math>
Common lenses angles of view
This table shows the diagonal, horizontal and vertical angles of view in degrees of lenses often used with 24×36 mm 135 film.
| Focal (mm) | 13 | 15 | 18 | 21 | 24 | 28 | 35 | 50 | 85 | 105 | 135 | 180 | 210 | 300 | 400 | 500 | 600 | 830 | 1200 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Diagonal (°) | 118 | 111 | 100 | 91.7 | 84.1 | 75.4 | 63.4 | 46.8 | 28.6 | 23.3 | 18.2 | 13.7 | 11.8 | 8.25 | 6.19 | 4.96 | 4.13 | 2.99 | 2.07 |
| Vertical (°) | 85.4 | 77.3 | 67.4 | 59.5 | 53.1 | 46.4 | 37.8 | 27.0 | 16.1 | 13.0 | 10.2 | 7.63 | 6.54 | 4.58 | 3.44 | 2.75 | 2.29 | 1.66 | 1.15 |
| Horizontal (°) | 108 | 100.4 | 90.0 | 81.2 | 73.7 | 65.5 | 54.4 | 39.6 | 23.9 | 19.5 | 15.2 | 11.4 | 9.80 | 6.87 | 5.15 | 4.12 | 3.44 | 2.48 | 1.72 |