Here are some of the causes:
Sensor size - Camera sensor size varies, the larger, more easily create a blurry background. Camera phones or compact cameras have a sensor size is relatively small compared with the digital SLR camera. In the digital SLR camera, subdivided some kind of sensor size.
The smallest to the largest are: Four thirds (ratio of 4 by 3), there is a crop sensor 1.6 (Canon), 1.5 (Nikon, Pentax, Sony), there is also a full frame (Nikon, Sony) and medium format (phase One, Leica S2, Pentax 645D).
Aperture - By using a large aperture lens (f/2.8 or larger such as f/1.4), then the background becomes more blurred.
No focus - This may be a result of the focus on the wrong part of the object, too close to the object so that the focus can not be obtained, the error selecting aperture that produces a very narrow depth of photo (smaller f number, e.g. f/2) or take photos too quickly without check first in the viewfinder.
The ratio of the distance between the subject of the picture with the camera and the distance between the subject with the background - The closer the camera is to the subject of the picture and the farther your subject with the background, the picture becomes more blurred.
Example: When the camera is on your subject distance of 10cm, and the distance of the subject of the image to the background of 20m, it can certainly be very blurred background. This is because the distance ratio of camera to subject and subject to background is very large.
Conversely if the distance of the camera to the subject of the picture 20m, and the distance to the subject of the photo background 10cm, it can certainly be a very clear background / sharp.
Lens focal length - The larger the lens focal length is used, then the background becomes more blurred. Example: Background photo taken with a 55mm lens focal length more blurred than when taken with a 18mm lens focal length.
Moving objects - is another form of photo blur due to take a moving object by using a slow shutter speed.
Camera shake - shake the camera is usually derived from the movement of the photographers themselves while taking pictures to produce photo blur.
Noise - The photos were found spots of the image pixels, usually derived from errors in setting the ISO, the more ISO noise level is also growing.
And here are additional tips to get sharp photos:
1. Hold the camera correctly when shooting
The best way to overcome camera shake when shooting is to use a tripod but it is not practical to carry because of its size that takes place. The practical way is to hold the camera properly.
2. Use the camera and lens that have Image Stabilization feature
Many cameras and lenses currently equipped with Image Stabilization (IS), which helps reduce the effects of camera shake when shooting so that the resulting images could be sharper. But keep in mind that IS only helps stabilize the camera movement is not stabilizing the movement of objects.
3. Use a good lens
If you have a higher budget then buy a better lens to get a sharper image quality than always using a standard lens. For Canon lenses, better quality for L-series lenses (professional series lenses).
4. Clean the camera equipment regularly
Each finished using the camera moreover used outdoors, do not forget to clean appliances such as camera lenses and camera sensor from stains, dust and dirt as it will affect the images (cause spotting on the photo).
The conclusion of this post is how to make the background out of focus photo becomes very blurry or bokeh?
The answer is:
- Use wide aperture lens
- Use longer focal length
- Note the distance ration between camera, subject and background
- Use camera with big sensor size.