focus
FOH-kuhs
/ˈfoʊkəs/
The state of maximum clarity and sharpness of an image, or the adjustment of a lens to achieve this.
Can be used as a noun (the point of focus) or a verb (the act of adjusting the lens). In photography, it refers to the exact plane where light rays converge.
The story behind the word. In ancient Rome, the 'focus' was the domestic hearth or fireplace. Because the hearth was the literal and metaphorical center of family life where everyone gathered, the word came to mean 'center of activity'. In 1604, the famous astronomer Johannes Kepler adapted the word to optics to describe the point where burning lenses concentrated light rays to a single, hot point.
Word relationships
- sharpness: 'Sharpness' is the visual perception of fine detail, whereas 'focus' is the physical convergence of light rays that produces that sharpness.
- blur: 'Blur' is the lack of definition or sharpness, which is the physical opposite of focus.
Commonly confused with
- zoom: Zooming changes how close or far the subject appears; focusing changes how sharp or blurry the subject appears.
Word family
- focal (adjective): Relating to a focus or a focal point.
- focused (adjective): Directing energy or attention; sharp and clear.
- focusing (noun): The act of adjusting to find focus.
Collocations
- sharp focus
- soft focus
- autofocus system
- manual focus
Idioms & expressions
- in focus
- out of focus
Example sentences
- "If the camera's autofocus struggles in low light, you can switch to manual focus to ensure your subject is sharp." A photography tutorial on manual focusing.
Memory hook
Think of a fireplace (focus) being the central point of a cozy living room where everyone gathers their attention. Focus on the center.
When not to use
Do not confuse with 'zoom', which changes the focal length (magnification) of the lens, not its sharpness.
Fun facts
- The mathematical and optical term 'focus' was chosen because if you hold a magnifying glass under the sun, the point where the light is perfectly focused is also the point that will catch fire.
Related words
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