Home >> Hobbies >> Other Hobbies

Why Do Photos Lose Sharpness at a Distance?

It is something every photographer -- be he a child using a camera for the first time or a seasoned professional -- notices: The farther away from a camera something is, the less sharp and more blurry it will appear. What the professional photographer understands, and the novice may not, is that the nature of lens focus and light are responsible for this.

Light Waves
- The images that humans perceive are composed of beams of light. The brain composes images from these beams when they pass through the human eye and fall on the human retina, which detects the characteristics of the beams and passes this information to the human brain. Cameras work in a similar way, only the beams of light trigger changes in film, or digital devices record the data into image files. The loss of sharpness at distances is the result of the way the beams are focused by the camera's lens.
Focusing Light Waves
- Beams of light reflect off the objects they hit and travel outward. Cameras, like humans, can turn these scattered beams of light into images because of lenses that refract, or bend, beams of light. Camera lenses are designed based on the lens of the human eye. In the same way the lens in the human eye bends disparate beams of light so that they all converge on the retina, the camera lens bends disparate beams of light so that they all converge on the camera's sensors. When the beams of light from a particular spot converge, then the image of what those beams bounced off of is sharp and in focus.
Lack of Sharpness
- Lenses, for both cameras and human eyes, are designed to focus the beams of light from a single location at a time on the camera's sensor. While the precise size of the area that a camera can bring into focus -- by making all the beams of light from it converge on a single spot -- varies from camera to camera, the parts of the image surrounding the focused area will be less sharp and more blurry. This is because the beams of light from these surrounding areas do not converge tightly on a single spot.
Distance
- The farther from the focused area a part of an image is, the more blurry it will be. This is because the further from the focused area the beams of light originate from, the greater the difference in the angle between those beams and the beams from the focused area will be. The less tightly the beams of light from a particular area converge on the camera's sensor, the more blurry the image will be.

Other Hobbies