The f-stop number is a ratio of the focal length of the lens to the diameter of the aperture. A lens is said to be "wide open" when it's set on its smallest f-stop, or with the aperture opened as wide as possible.
F-stops in particular have a tremendous effect on image characteristics, some of which may not be obvious to amateur shooters. For the bulk of this article, we'll discuss and improve your grasp of the mysterious f-stop.
F-stops are sometimes used to describe changes in amounts of light, not directly related to aperture. For example, an image stabilisation system might be described as allowing handhold-able shutter speeds three stops slower than normal.
F-stop and aperture are by far the most complicated and most confusing aspects to exposure control and composition.
Small F-Stop = Small Depth of Field = Less Light Needed
This means that larger F-Stops, such as F11, will require slower shutter speeds and produce images with larger depths of field.
You can begin to make use of the power of the f-stop when you're taking those candids at home. This is a job for the wide open f-stop, a setting of f/4 or so.
Each full f/number, also called a stop or f-stop, halves or doubles image brightness and some lenses can also be controlled in half or third steps. The most common f/numbers are 1.4, 2, 2.8, 4, 5.6, 8, 11, 16 and 22.
f-stop
Useful for determining the maximum flash to-subject distance for flash photography.
Fill-flash : ...
F-Stops are different numbers that are assigned to the different aperture sizes.
F-stop
F-stop is the mathematical value of the size of the aperture; while the actual aperture hole varies in size depending on the focal length of the lens, ...
F-Stop
Standard unit of exposure. A means of expressing the illuminating power of a lens regardless of its focal length.
freeware ...
F-stop
The term used as a measurement corresponding to the size of the opening in a camera lens. The standard numbers used are typically stated as f/1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, etc. The f/1.
F-Stop or F-Number - number used to measure the size of the camera's aperture
Fill Flash - flash used on a bright day to fill in harsh shadows ...
F-stops
A thorough explanation of f-stops: what are common f-stop values and how a difference in one ‘stop’ will influence your photo?
Focus ...
F-stop also known as f-number, this is the measure used to determine the relative aperture size of a lens. It is calculated by dividing the diameter of the aperture opening by the focal length of the lens.
F-STOP- The f-stop of a lens is a number that represents the aperture opening. A large opening is a small f number, and a small opening is a large f stop. Lenses are rated in the range of f-stop numbers they can be set to.
f-stop. A numerical designation (f/2, f 2.8, etc.) indicating the size of the aperture (lens opening).
GIF. An image file format designed for display of line art on the Web.
f-stop:
A means of measuring the width of the diaphragm opening, which determines how much light passes through the lens.
F-Stop . 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.
f-stop. The relative size of the lens aperture, which helps determine both exposure and depth of field. The larger the f-stop number, the smaller the aperture.
f-stop see Stop
Fall-off (Light on a surface)
The size of the area on a surface where light and shadows merge. Soft sources produce a gradual transition, a subtle gradation of tones. Hard sources, without Fill Light, change abruptly.
f-stop
fixed sizes at which the apperature of the lens can be set; a number established by dividing the focal length of a lens by the diameter of the lens opening.
ft
abbreciation for foot.
F-stop
A number that indicates the relative size of the opening of the lens (aperture) and written, for example, as f/16.
F-stop
A term used to describe the aperture, or opening of a lens. F-stops are defined numerically - f1/4, f5.6, f22, etc. Larger, or wider apertures, allow more light to enter the lens, which results in faster shutter speeds.
Bigger f-stop numbers create bigger depth-of-field (and, thus, more of everything in the picture remaining in focus).
F-stop values are traditionally incremented by stops. Each stop is a standard value that allows half as much light through as the previous stop and twice as much light as the next stop.
F-stop - The optimum f-number for landscape photography is considered to be either f11 or f13. My preferred f-stop is f11 as I find that this gives you the maximum depth of field without any diffraction occurring.
Step 8 ...
f-stop
A number indicating the size of the diaphragm's aperture in a lens. An f-stop number is not a constant measurement, but is calculated from the size of the aperture and the focal length of the lens. On a given lens an aperture of f2.
f-stop number = GN / distance
distance = GN / f-stop number
Canon's guide numbers are measured in metres and are for ISO 100.
(f-stop) Numbers on the lens barrel indicating the size of the aperture relative to the focal length of the lens. f numbers are calculated by dividing the focal length of the lens by the effective diameter of the aperture.
The f-stop you set on your lens also has an effect on the sharpness of your pictures. All lenses are at their sharpest when closed down two to three stops from their widest apertures. Try to avoid the widest and the slowest f-stops if possible.
14. F-stop: The number assigned to a particular lens aperture (or opening) size.
15. Film: A piece of plastic with a light sensitive mixture spread on it.
chosen f-stop: 5.6
max. distance = 80 / 5.6 = ~14.2 meters
Note: If you have to go to the limit it is usually not such a good idea to place your subject at the calculated max. distance.
There are f-stops that simply won't deliver a proper TTL exposure. At a certain point, the strobe will have dumped full power, and at that given strobe-to-subject distance, a smaller f-stop can't work.
With 0.9, 3 f-stops grad ND filter
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There are times when two filters are required, combined, like in the sunrise image at right, which needed both a 2 and a 3 f-stops graduated density filters, the second one placed diagonally.
There are 5 f-stops between the max and min aperture. If your camera's lens is currently set at an aperture of F5.6, closing it by 1 f-stop would mean selecting F8; opening it up by 1 f-stop would mean selecting F4.
F1.8
F2.8 ...
Aperture, F-stop A camera's aperture works like the iris of your eye, expanding and contracting to adjust the amount of light which passes through. The smaller the aperture, the less light it admits.
Adjust your f-stop as needed for greater DOF or blurred background. your TTL converter will control the strobe power
Macro, strobes in manual mode (you don't have a TTL converter): ...
F
F-Number, F-Stop
See Aperture.
Fill-In Light
Additional light from a lamp, flash, or reflector; used to soften or fill in the shadows or dark picture areas caused by the brighter main light. Called fill-in flash when electronic flash is used.
f numbers
f-stops
A numerical designation (f/2, f 2.8, f3 etc.) indicating the size of the aperture.
Firewire ...
F-numbers or F-stops
Numbers on the lens aperture ring and the camera's LCD (where applicable) that indicate the size of lens aperture. The lower the number the larger the aperture. As the scale rises, each number is multiplied by a factor of 1.4.
[edit] Stops, f-stop conventions, and exposure
A Canon 7 mounted with a 50 mm lens capable of an exceptional f/0.95 ...
Most lenses have f-stops that are represented numerically by integral powers of the square root of two. Common f-numbers on a lens are f/1, f/2, f/4, f/8, etc.
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so in the end the f-stop tip is quite nice because the math checks out. but the explanation of why this is so was bogus.
ƒ-stop - (f-stop or F/stop) A lens aperture setting calibrated to an f-number (see above).
FALLOFF - Decrease in the intensity of light as it spreads out from the source.
Learn about your "f-stop".[3]"F-stop" (also called "f-number") means fraction and the f-number is the fraction of the actual opening in the lens compared to the focal length of the lens. The aperture is the opening light passes through.
3 ...
The aperture diameter is expressed in f-stops; the lower the number, the larger the aperture. For instance, the aperture opening when set to f/2.8 is larger than at f/8.
Measured in f-stops. Altering by one F-stop either halves or doubles the amount of light reaching the film. Top
B
Top
C
contrast Relationship between tones on negative or print.
You need to set a very small aperture (large f-stop number). I therefore use Aperture Priority Mode (Av on most Cameras) and place the camera on a tripod, since a small aperture usually results in a long exposure time.
One f-stop of light gathering capability, which is huge. Add to that the sensor-based image stabilizer and you have some capabilities that would make a Canon EOS user drool.
Olympus 12-60mm f/2.8-4.
Photographers know that if they choose a high f-stop, such as ƒ/16 or ƒ/22, they can expect great depth-of-field with much of the foreground and background in focus. Choosing a low f-stop, ƒ/2.
The Zone System is an 11-step gradation of reality, from pure black to pure white, and each step equates to one full f-stop.
As a brief aside here, the exposure required for a given star at a given ISO setting doesn't depend on the f-stop of the lens. This may seem odd, but it's true. Exposure depends on f-stop only for extended objects.
Controlling the aperture is an advanced technique which allows you to control the width of the lens opening (like the iris of an eye), allowing for more direct control over how much light enters the camera, and is normally referred to as an 'F-stop' ...
Discussions as to f-stops and shutter speeds are almost as boring as cleaning "0" rings. THE BEST WAY TO GET THE CORRECT EXPOSURE IS TO GUESS. Being lucky is a great help for a budding underwater photographer.
Aperture settings are called f-stops and indicate the size of the aperture opening. Each f-stop lets in half as much light as the next larger opening and twice as much light as the next smaller opening.
There is no real need for you to know what these numbers stand for other than to know that the smaller number (f-stop), say f4, will let more light through the lens.
The size of the aperture is measured using an f-number also called the f-stop (F8, f/8, etc). The smaller the f-number, the larger the camera's opening. The size of the aperture directly affects depth of field and shutter speed.
If your shot comes out too dark, increase your aperture (increase your f-stop number). And if your shot is too overexposed, decrease your aperture (lower your f-stop). Aperture will affect your depth of field also.
The aperture on a camera, which is measured in f-stops, does exactly the same thing by controlling the amount of light that reaches the CCD.
 See also: Camera, Light, Lens, Image, Digital
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