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Technically, it doesn't do anything because it's a measurement of how many times the aperture size fits into the lens focal length.
Let's consider a picture taken using an F-stop like 5.6 (written as F 5.6) on a 50 mm lens. The diameter of the physical opening created by the aperture blades when they are "stopped down" will fit into the focal length 5.6 times. It's not important that this works out to about 8.93 mm in this case, but this may help understand the next concept. If the lens is 300 mm, you should realize that in order to fit into that focal length 5.6 times, the aperture would have to be about 53.6 mm. This explains why the optics in long focal length lenses are larger and the practical limit for their minimum aperture (the smallest number but the largest size, if you've grasped this) goes up. If you're now wondering what effect the F stop has on a picture, it is this...
Larger apertures (e.g. F 2.8) give you less depth of field in the photograph than small ones such as F11. Depth of field is the distance before and after the principle plane of focus (the plane in space that the lens is actually focused on) that appears acceptably sharp to the naked eye. Depth of field is not to be confused with depth of focus. If you are really curious and masochistic, look up hyperfocal distance on this web site.
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What does fstop mean?
An F Stop refers to a ratio used in a camera lens. It is concerned with the amount of light the lens lets in, how fast the camera can take a picture, and how much of the picture will be in focus. With pixels, it is possible to overcome some of the restrictions of film cameras. First, if you have a low f stop, like 1.2, and you have a lot of light, you can take a picture real fast. Only the object you focused the camera on will be in focus. If you use a high f stop, like 22, you will need to slow down your shutter speed. Your subject will be in focus and so will the background. The old point and click cameras had about a shutter speed of 1/125 of a second, a distance of 8 feet, and an f stop of about 8. The person would be in focus. The background would not.
What is apperture?
The main function of a camera lens is to collect light. The aperture of a lens is the diameter of the lens opening and is usually controlled by an iris. The larger the diameter of the aperture, the more light reaches the film / image sensor.Aperture is expressed as F-stop, e.g. F2.8 or f/2.8. The smaller the F-stop number (or f/value), the larger the lens opening (aperture).
How can I calculate the right depth of field while taking a photo?
If you're using a DSLR (digital single lens reflex) camera, you need to have it set to Av (aperture priority). The lower your aperture, the less depth of field and vice versa. If you're using a point and shoot camera, you cannot manually control your aperture settings, the various modes do that for you.
What does 12.5 mean on the shutter speed?
It depends on where you are seeing this number. Most shutter speed conventions do not use o1/12.5 of a second as a shutter speed; the closest would probably be 15 meaning 1/15th of a second, which is a very long/slow shutter speed usually producing blurs if you're not using a tripod. I can't think of a camera with that as a preset shutter speed but your camera might. You may possibly be looking at an intermediate f-stop (between 11 and 16) being reported on your screen or wherever these are shown (your LCD?) when you are in shutter priority mode where you are setting a fixed shutter speed and then the camera automatically adjusts for f stop (aperture) based on WB and ISO and is sophisticated enough to report an f-stop between 11 and 16).
What is the melting point of a camera?
A camera is made of a variety of materials with melting points from about 110 C (230 F) for some of the polymers on up to over 1000 C (1850 F) for some of the metals. Subject any camera to heat above 80 C (180 F) for an extended period of time and it will probably fail.
