f-number love

# f-number

## Definitions

### from The American Heritage® Dictionary of the English Language, 4th Edition

• n. The ratio of the focal length of a lens or lens system to the effective diameter of its aperture. Also called f-stop.

• n. The ratio of the focal length of a lens to its diameter; a measure of the light-gathering ability of the lens.

## Etymologies

### from The American Heritage® Dictionary of the English Language, 4th Edition

f(ocal length) + number.

## Examples

• Blaker explained this in another book, Field Photography (1976): ... at significant magnifications the choice of f-number is ... nearly always a matter for compromise between depth of field needs and the resolution of fine detail in the image.

Archive 2009-06-01

• If your camera has manual controls, you can add more light to your shots by opening the aperture more widely (using a smaller f-number) and slowing the shutter speed (to, say, 1/125 or even 1/60 of a second).

Tips: 5 digital camera mistakes to avoid

• Blaker explained this in another book, Field Photography 1976:...at significant magnifications the choice of f-number is...nearly always a matter for compromise between depth of field needs and the resolution of fine detail in the image.

Depth of field, f-numbers and diffraction (or how to take a rotten photograph)

• Each "stop" is marked with its corresponding f-number, and represents a halving of the light intensity from the previous stop.

Further aspiration.

• The literal interpretation of the f/N notation for f-number N is as an arithmetic expression for the effective aperture diameter (input pupil diameter), the focal length divided by the f-number: D = f/N. Noooo!!!

Further aspiration.

• On a camera, the f-number is usually adjusted in discrete steps, known as f-stops.

Further aspiration.

• To do this, choose a small aperture, which will be denoted by a larger f-number.

Macworld

• First, it's tempting to just dial in the largest f-number you can, but this is usually a bad idea.

Macworld

• In addition to considering focal length, pay attention to the "speed," or f-number, of your lens.

PCWorld

• The easiest way to control the depth of field is to set your camera to its aperture priority mode and then dial in the biggest aperture (the smallest f-number) that your lens allows.

PCWorld