F-stop este un raport intre distanta focala a obiectivului si diametrul diafragmei; se mai numeste si f-number si se scrie f/2 ceea ce înseamna diafragma are un diametru egal cu jumatate din distanta focala; fiecare valoare permite intrarea in aparat a jumatate din cantitatea permisa de diafragma imediat mai mare si de doua ori mai multa decât diafragma imediat mai mica; valorile standard cele mai frecvent întâlnite sunt: f/1,4 f/2 f/2,8 f/4 f/5,6 f/8 f/11 f/16; de notat ca numitorii se afla in progresie aritmetica cu ratia SQRT(2); termenul dateaza de pe vremea când ajustarea diafragmei se facea prin rotirea unui disc cu gauri de diferite diametre si a ramas in vigoare si pentru obiectivele actuale, cu diafragma tip iris.
Number indicating the size of the aperture. It is an inversely proportionate number as in F2.8 is a large opening and F16 is a small opening.
A term used to describe the aperture, or diaphragm opening of a lens. F-stops are defined numerically: f/1.4, f/5.6, f/22, etc. Larger, or wider apertures, allow more light to enter the lens, which calls for faster shutter speeds. Faster (wider) apertures also allow for selective focus (narrow depth of field), while slower (smaller) apertures allow for greater depth of field. Wider apertures are preferable for portraits, while smaller apertures are preferable for landscapes. For more on this subject, see the explora article, ://www.bhphotovideo.com/explora/photography/tips-and-solutions/understanding-aperture Understanding Aperture.
is a measure of the aperture opening in the lens defined by dividing the focal length of the lens by the aperture diameter. Sequence of f-stops are multiples of the square root of 2 (1.414…): 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, etc. Even though these numbers are rather cryptic, just remember that each step is double the amount of light. Know that and it’s half the battle.
– A diaphragm inside the camera lens, known as the aperture, can be opened or nearly closed, to regulate the amount of light that falls on the image sensor. The ratio of the lens s focal length to the diameter of the opening is the f-number, or f-stop. Due to the way the values are calculated, the smaller numbers (f1.2, f2.4) actually represent wider openings. Each full f-stop represents a doubling or halving of light. For this reason, photographers often describe shutter speeds in f-stops as well. For example, a shutter speed of 1/60 second is one stop less than 1/30 second.
Another term for the numbers on the aperture of a camera lens. May also be referred to as “stops.”