Depth of field
The big (f/1.8) aperture and close focus distance app 30cm (1′ )
results very shallow Depth of field. (Blurred background)
What the depth of field is ?
To understand what depth of field often referred Dof means, first must understand what aperture is. You can learn by clicking the link at the top of the page. In short depth of field is the sharp zone on the picture. The sharpest spot where we focus the camera, but behind (background) and little closer(foreground) can be sharp as well. The size of this Dof is different on different cameras. If the camera sensor is bigger the sharp zone is smaller with otherwise same settings.
Factors that influence Dof
1. Distance of the focused object. If we focus closer the Dof is shallower, if we focus at more distance the Dof is deeper.
2. Aperture setting. With bigger apertures (smaller number f/1.4 for example) the Dof is shallower, with smaller apertures (f/11-f/16) the Dof is deeper.
3. Lens focal length. Wider lenses has more deep dof, longer lenses has Shallower Dof.
4. Camera sensor size.
The Dof is bigger if the sensor is smaller or the Dof is thinner if the camera sensor is bigger.
The above picture was made with a Full frame camera with a 70-200mm lens at a very close distance. This factors lead to a very shallow depth of field. You can check even the ends of the leaf are out of focus. The focus is around the lower part of the image on the leaf.
Deep Dof is preferred for landscapes and for macro photography most. If we want a dramatic landscape we want everything in the focus from the really close objects to the really far objects as well.
The above picture was made with a wide 10-22mm lens. The really wide lens helps to bring most of the picture in focus.