Back to Basics - Depth Of Field
After discussing exposure in great detail, I would like to turn to a different kind of control - Depth Of Field (A.K.A. DOF). OK. Don't jump - you are right. Depth Of Field is not a real control, but more of a result of how you used the aperture control.
In simple words Depth of field is the term you use to describe what is inside the focused area of your image and what is left outside of the focused area (and will stay home alone, and eat dry bread and drink stale water. Sorry Jewish mom syndrome...)
As I said before the control that has the most impact on depth of field is aperture. Bigger apertures tend to provide shallower depth of field. That means that if you open a wide aperture (say f/1.8) you will have a narrow location in your image which is focused. If you set your aperture to a small value, say f/22, you will have a huge focused area. The other two controls you can employ to control depth of field are Zoom focal length and camera to object distance.
To conclude the first part - Depth Of Field controls what is in focus. If you are inside the field you will look sharp. If you are outside the field you will look blurred. If you want to be sharp - Stay in the field!
Here is a fact about depth of field
- Depth of field has two sides - a short side that goes from the object to the camera, and a long side from the object away from the camera. the long side (i.e. object and away is twice as long as the short side).
Depth Of Field and camera to object distance - The second control you can employ to control depth of field is the distance between the camera and the object you are shooting. The greater this distance is the more depth of field you will have.
Depth Of Field and zoom focal length - The longer focal length you use, the shallower depth of field you will have. And of course, you will need a faster shutter speed to compensate for hand shake. This is why pictures shot with a fish eye lens (15 mm or less) looks sharp across the board.
Image by dsevilla (aperture = f/5.6, focal length = 300mm)
Shallow Depth Of Field - Shallow depth of field means that a small portion of the picture is in focus. This is usually accomplished by using wide apertures.
Image by wisdoc (aperture = f/5.6, focal length = 135mm)
Great Depth Of Field - great depth of field means that a big portion of the picture is in focus. The image below uses a relatively close aperture. Great Depth of field is achieved by using the short focal length of the point and shoot camera.
Image by 2composers (aperture = f/6.3, focal length = 6.3, Powershot SD30)
Depth Of Field and macro - Basically, there are two approaches for taking a macro shot - use very small aperture and get sharpness all across the image, or use a small aperture and get an artistic effect. For small apertures you will probably need some flash assistance to get more light into the sensor make sure you diffuse it well.
Image by mdezemery (aperture = f/18, focal length = 35mm)
Depth Of Field and landscape - for shooting landscape, photographer often use a small aperture along with setting the lens at its magic area hyperfocal distance. Don't be alarmed! Hyperfocal distance is simply the point that if you focus your camera to, you will get sharpness from close to infinity. I will write about that soon.
Image by The International Rice Research Institute (aperture = f/10)
Shallow Depth Of Field and portraits - You can take portraits with any depth of field you desire. Usually the most important rule is to keep both eyes within the depth of field. The image below was shot with a very shallow depth of field. It earned the photographer a nice bokeh. It looks good because both eyes are sharp.
Image by perryge (aperture = f/1.8, focal length = 50mm)
Depth Of Field self assignment - pattern breaker
Make some arrangement of things in a pattern, or find some pattern in your surrounding - windows, book shelves, bridges - they all make good patterns.
Try and take several pictures of the same pattern several times. For each series of shots change one parameter:
- keep the aperture and framing of the picture unchanged and take a series of pictures changing the zoom.
- keep the zoom and framing of the picture unchanged and take a series of pictures changing the aperture.
- keep the aperture and zoom unchanged and take a series of pictures changing the framing, each time make the center of the image closer to you.
Compare the three series you took; which control makes the greatest impact on depth of field?
Image by bullish1974