Lens Aperture 


What you need to know

  • The aperture is like the pupil in your eye; when it is larger it lets more light in and visa versa.  
  • a larger aperture allows more light to expose your sensor and a smaller one lets less light through.  
  • It is commonly referred to as an f-stop or f-number and if you move from one aperture to the next that is considered one stop.
  • Each stop represents either half or double the amount of light exposing the film or chip 
  • The numbers are in fractions, so the larger numbers represent smaller apertures and visa-versa.  
  • The fraction= focal length of the lens/aperture diameter
  • If you stop down from 2.8 to 4.0 your are halving the amount of light exposing your film or chip.  
  • If you stop up from 8.0 to 5.6, you are doubling the amount of light exposing your film or chip.
  • F-stops are logarithmic to base 2, so if you close two stops you quarter the amount of light. Brown (49)
  • The larger the aperture the less depth of field you will have in your image.  "What we perceive as acceptable focus that extends in front of and behind the subject we are focusing on" Brown (49)