Depth of field

1. Depth of field Depth of the field (DoF) is the distance between the nearest and farthest objects that appear acceptably sharp. DoF depends on focal length, aperture (while adjusting shutter speed and/or light sensitivity to compensate for changes in aperture), distance from the subject to the lens and sensor type. Changes in distance and focal length affect DoF, but these changes have trade-offs in terms of composition. Therefore, changes to aperture are the best way to manipulate DoF without affecting a photo’s composition.

2. Aperture • The aperture is the opening at the rear of the lens that determines how much light travels through the lens and falls on the image sensor. The size of the aperture’s opening is measured in f-stops - one of two sets of numbers on the lens barrel (the other being the focusing distance). The f-stops work as inverse values, such that a small f/number (say f/2.8) corresponds to a larger or wider aperture size, which results in a shallow depth of field; conversely a large f/number (say f/16) results in a smaller or narrower aperture size and therefore a deeper depth of field.

4. Shutter speed • Shutter speed is the amount of time that the shutter is open • Measured in seconds • For example if you speed up your shutter speed one stop (for example from 1/125th to 1/250th) you’re effectively letting half as much light into your camera. To compensate for this you’ll probably need to increase your aperture one stop (for example from f16 to f11). The other alternative would be to choose a faster ISO rating (you might want to move from ISO 100 to ISO 400 for example).

5. Focal length • The distance from the lens to the film, when focused on a subject at infinity. Focal length equals image distance for a far subject. To focus on something closer than infinity, the lens is moved farther away from the film. This is why most lenses get longer when you turn the focusing ring. The distances follow this formula: 1/Image + 1/Obj = 1/focal length • F-stop is the focal length divided by the diameter of the lens. For example, a 200mm f/4 lens will be 50mm wide. The longer the focal length is, the shallow the depth of field will get. If you shoot something with a 50mm lens at f/2.8 and then shoot the same thing with 200mm lens at f/2.8 the difference in the depth of field is going to be dramatic.

6. ISO • Indicates how sensitive is the film/sensor to light • The lower the number, the less sensitive, and the finer grain in shots • Higher ISO settings are generally used in darker situations to get faster shutter speeds

7. Jani Huttunen • Focal length: 50 mm • Exposure time: 1/500 sec • F-stop: f/1.4 • ISO: 6400

8. Focal length: 50 mm • Exposure time: 1/500 sec • F-stop: f/1,4 • ISO: 6400

9. Focal length: 50 mm • Exposure time: 1/200 sec • F-stop: f/4.5 • ISO: 1640

10. Focal length: 50 mm • Exposure time: 1/200 sec • F-stop: f/4.5 • ISO: 6400

11. Gabrielė Čiužauskaitė • Focal length: 50 mm • Exposure time: 1/125 sec • F-stop: f/2 • ISO: 200

12. Focal length: 50 mm • Exposure time: 1/125 sec • F-stop: f/2 • ISO: 200

13. Zuzana Bubenová • Focal length: 24 mm • Exposure time: 1/10 sec • F-stop: f10 • ISO: 1000

14. Focal length: 24 mm • Exposure time: 1/40 sec • F-stop: f4 • ISO: 1000

15. Focal length: 50 mm • Exposure time: 1/640 sec • F-stop: f/9 • ISO: 6400 • Focal length: 50 mm • Exposure time: 1/640 sec • F-stop: f/8 • ISO: 6400