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2.1 What is shutterspeed?

The number that appears on a camera's shutter dial or in its LCD panel is the shutter speed. A shutter speed shorter than one second (value indicated as 1/__) means the shutter remains open for that amount of time, during which the film is exposed. If the number reads "500," then the shutter will remain open for 1 / 500 sec. If the shutter speed is longer than one second, the number will be a different color; on an LCD panel you'll see an "S" (for "seconds").

On most cameras, shutter speeds can be set to the times listed below. Some cameras allow you to set shutter speeds between these times, while others allow an infinite number of speeds.

These numbers, depending on how you look at them, occur in halved or doubled increments.

Each of these increments is called a step. For example, if shutter speed moves two(2) "halves," it moves two "steps." This is significant when determining exposure. Additionally, the shutter indicator/dial will contain letters, usually T, B or X. What do these signify ?

* T (Time) The front curtain opens when the shutter release button is pressed and remains open even after the button has been released. When you press the button again, the rear curtain travels to close the shutter. This is effective for long-time exposure, which might take few minutes.

* B (Bulb) The shutter remains open while the shutter release button is depressed and closes only after the button is released. This is a useful feature for shots that require a long exposure time. This is effective for long-time exposure, which might take few seconds.

* X, or a lightning bolt graphic (sync shutter speed / "X" contact)
This is the fastest shutter speed you can select when using a speedlight, also known as an electronic flash.
Maximum synchronizing shutter speed varies depending on the shutter mechanism; shooting with a speedlight should be done with a shutter speed slower than the X speed.

Accordingly, if a speedlight flashes at the same time as a shutter set at a very fast speed, only a thin portion will be exposed. The speedlight must flash when the shutter is fully opened.
The "X" shutter speed is the fastest speed at which the shutter fully opens.

Certain cameras can automatically set the shutter speed so it doesn't exceed the "X" speed when being used with a charged speedlight, which sends a signal to the camera.
Thus, if you are setting the shutter speed manually, you must be more cautious when taking pictures using speedlight.

2.2 Shutter speed and picture brightness

The slower the shutter speed, the longer the film is exposed to light. As the amount of light hitting the film increases, the picture's brightness increases. Many people think it's not possible to take photos in dark places, but this is just not true. In places light enough for us to see our surroundings, a picture can come out bright if the shutter speed is very slow. This said, it is possible to take photos under pale moonlight, or even with illumination from a flashlight.

There are certain conditions necessary for taking such pictures, though. Obviously, the subject should not be moving.
The camera must be held very still, with a tripod if possible, and the shutter should be controlled with a self-timer or remote release.
If there is artificial light — a street light, for example -- in the picture, then overexposing the photo with an extended shutter speed is a good idea.
Please note that not all film that has been exposed for a long time will turn out satisfactorily. Exposure time affects film sensitivity, and the longer the exposure, the less sensitive the film becomes (known as reciprocity law failure).