Photography & Imaging

Basic

F-Number

Aperture f-number is focal length divided by aperture diameter.

Formula

N = \frac{f}{D}

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Variables

NF-number

fFocal length (mm)

DAperture diameter (mm)

Example

50 mm lens, 25 mm aperture: N = f/2

Did You Know?

Each full f-stop (f/2 → f/2.8 → f/4) halves the light by increasing N by a factor of √2.

photography aperture f-stop

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More in Photography & Imaging

Exposure Value (EV)

Combines aperture and shutter speed into one exposure figure.

Depth of Field (approx.)

Range of distances that appear acceptably sharp.

Hyperfocal Distance

Focus distance that keeps everything from H/2 to infinity sharp.

Lens Magnification

Image magnification from focal length and subject distance.

Angle of View

Field of view from sensor size and focal length.

Equivalent Focal Length

Focal length on a crop sensor expressed in full-frame terms.