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    • Argus C3
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    • Konica Auto S
    • Konica Auto S2
    • Konica SII
    • Minolta AL
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    • Minoltina AL-s
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    • Zorki 10
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  • Cameras
  • Gallery
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Focal Length & Aperture

The two fundamental parameters of a camera lens

With the lens focused at infinity, the Focal Length is the distance (specified in mm) measured from the centre of the front lens element to the focal point in the camera, indicated by the Focal Plane Mark on the camera body. The focal length determines the angle-of-view, short focal lengths giving a wider AOV than longer focal length lenses.

The aperture is the opening of the lens that determines the volume of light that is let through to expose the film. The aperture is variable and the size is indicated by a series of numbers known as f-stops or f-numbers, which are found on the aperture ring of the lens. The aperture is controlled by the diaphragm, and their relationship can be compared to that of the iris and the pupil of the eye. The iris (diaphragm) controls the size of the pupil (aperture). In a dimly-lit room, the pupil needs to be wide open to allow lots of light through to register an image; the opposite applies in bright light, when it has to shrink to minimise the intensity of light.

  • Rangefinder Cameras
  • Focal Plane
  • Focal Length & Aperture
  • f-stop
  • Numbers on a lens
  • Prime lens
  • Fast lens
  • Angle-of-view (AOV)
  • Elements & Groups
  • Coatings
  • Leaf shutters
  • Shutter speed
  • Film speed ASA/ISO
  • EV / Exposure Value
  • LV / Light Value
  • LV Tables
  • Priority
  • Depth-of-field
  • Bokeh
  • Apparent Subject Motion
  • Light meters
  • Be meter free
  • The Sunny 16 Rule
  • Double & half
  • Parallax
  • Rangefinder Vs. SLR
  • Filters
  • Filters: UV
  • Filters: Skylight
  • Filters: Polarizing
  • Filters: ND
  • Filters: Black & White
  • Diffraction
  • Multiple Exposures
  • Sharpest Aperture
  • C-41 B&W
  • Zone focusing
  • Half-frame
  • Vignetting
  • Guide Number
  • X & M
About Ilott Vintage

A valuable reference for anyone wanting to learn more about rangefinder cameras, manual film photography, or both, this website is intended to serve not only as a resource to discover some amazing objects but also as a place to learn more about them, to understand exactly what they are capable of, and why. Read More

See Also
  • Minoltina AL-s Nobody loves a fat camera
  • Zorki 10 Soviet style
  • Argus C3 vintage rangefinder
    Argus C3 The Brick
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    Wednesday 22nd March 2023