Focus
Focus is the tendency for light rays to reach the same place on the image sensor or film, independent of where they pass through the lens. For clear pictures, the focus is adjusted for distance, because at a different object distance the rays reach different parts of the lens with different angles. In modern photography, focusing is often accomplished automatically.
The autofocus system in modern SLRs use a sensor in the mirrorbox to measure contrast. The sensor's signal is analyzed by an application-specific integrated circuit (ASIC), and the ASIC tries to maximize the contrast pattern by moving lens elements. The ASICs in modern cameras also have special algorithms for predicting motion, and other advanced features.
Read more about this topic: Science Of Photography
Famous quotes containing the word focus:
“I don’t have any doubts that there will be a place for progressive white people in this country in the future. I think the paranoia common among white people is very unfounded. I have always organized my life so that I could focus on political work. That’s all I want to do, and that’s all that makes me happy.”
—Hettie V., South African white anti-apartheid activist and feminist. As quoted in Lives of Courage, ch. 21, by Diana E. H. Russell (1989)
“When Western people train the mind, the focus is generally on the left hemisphere of the cortex, which is the portion of the brain that is concerned with words and numbers. We enhance the logical, bounded, linear functions of the mind. In the East, exercises of this sort are for the purpose of getting in tune with the unconscious—to get rid of boundaries, not to create them.”
—Edward T. Hall (b. 1914)
“While the focus in the landscape of Old World cities was commonly government structures, churches, or the residences of rulers, the landscape and the skyline of American cities have boasted their hotels, department stores, office buildings, apartments, and skyscrapers. In this grandeur, Americans have expressed their Booster Pride, their hopes for visitors and new settlers, and customers, for thriving commerce and industry.”
—Daniel J. Boorstin (b. 1914)