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Hi Reshinda, Maybe you did not ask for this but the teacher in me makes me do it. Normally the camera shutter winks open for just a fraction of a second. During this short time, light from the outside world, focused by the lens is caused to be projected onto the film or digital sensor. A wink is all that’s needed most of the time. When the wink is competed there are three possibilities.
a. Too much light was delivered to the film or digital camera chip and the picture is ruined or is substandard due to over exposure.
b. Too little light was delivered to the film or digital chip and the picture is ruined or substandard due to under exposure.
c. Exactly the right amount of light energy was recorded and you produced a masterpiece. If too much light was delivered we might want to wait for dimmer conditions.
If too little light was delivered we could wait for a brighter sundrenched day.
Both above conditions might be counteracting by just adjusting the lens aperture. We can cause more or less light to enter the camera this way
If the scene is too dim we can induce artificial light.
If the scene is too bright we can erect some shade. We could change film/chip to a higher or lower ISO value. Maybe one of the above would work for you but maybe none are practical. We still have one more trick up our sleeve. We can change the duration of the wink.
You see film or digital chip accumulates light energy over time. We can cause the camera to wink for just a fraction of a second (usually the case). Or we can allow light to accumulate for a long time over many seconds. Each has pluses and minuses. Most of the time we want a short wink because camera movement or subject movement usually results in a blurred picture. Most folks can handhold a camera when the shutter is set to 1/30 of a second or shorter. For fast moving subjects or a heavy cameras or a camera with a telephoto lenses, we need a fast wink. Sometimes when light conditions are poor we need a wink that lasts for several seconds. When the duration is longer than 1/30 of a second we usually need to support the camera with tripod or other mount. Now consider that the shutter speed changes should be in some logical increment. The increment deemed most logical is a 2x change in time (double or half).
Consider this sequence:
30 - 15 - 8 - 4 – 2 – 1 – 1/2 – 1/4 – 1/8 – 1/15 – 1/30 – 1/60 – 1/125 – 1/250 – 1/500 – 1/1000 – 1/2000 The whole numbers are the duration in seconds. The fractions are the duration in fractions of a second. Saying or writing 1/15 – 1/30 is repetitious – we shorten this fraction be dropping off the 1/. Your camera shutter settings follows this logical sequence. Now you need to read the instruction manual and a beginners text on photography. Best regards, Alan Marcus
ammarcus@earthlink.net
October 22, 2006
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