DISCLOSURE: "THIS POST MAY CONTAIN AFFILIATE LINKS/BANNERS, AND THE SITE MAY EARNS A SMALL COMMISSION WHEN YOU BUY THE PRODUCT AT NO ADDITIONAL COST TO YOU. WE RECOMMEND THESE PRODUCTS BECAUSE OF THEIR TOP QUALITY AND LOW PRICES".
Lens opening. A perforated plate or adjustable opening mounted behind or between the elements of a lens used to control the amount of light that reaches the film. Openings are usually calibrated in f-numbers.