For anyone that was interested in the discussion that followed George Tallabas' post titled The Big Camera That Can't, I thought I'd put together a little information on the basics of Photography ... All you photo pros lurking here in Active Rain, (you know who you are) please do feel free to comment, or better yet, write your own blog and tag it for the Photography Group.
I am not a pro, just a garden variety hobbyist, but here goes:
Compact consumer-level point-and-shoot digital cameras have become a standard household item. Almost as common as a toaster. And since many people now begin their interest in photography with just such a camera, they might not be "exposed" (pun intended) to some of photography's basic concepts.
Photographic exposure consists of three basic components, regardless of whether you are using film or digital:
Shutter speed: The shutter is a small movable panel or blade inside the camera that quickly opens and closes again, in front of the film or digital sensor, When you press the shutter release button. The shutter controls the amount of time, measured in fractions of seconds, that light is allowed to hit the film or digital sensor. For instance, Canon's EOS30D has a top shutter speed of 1/8000 of a second. A compact point-and-point digital camera may not have a physical shutter. Instead the sensor may be programmed to quickly turn on and off again to mimic a physical shutter.
Lens aperture: The aperture is the small circular opening in the lens that light must pass through to hit the film or digital sensor. That opening can very small, or it can be large. The larger the diameter of the aperture opening, the more light strikes the film or digital sensor. The aperture size is stated as "F-stop". The lower the F number, the larger the aperture opening ; for instance f/2 is a very wide opening, f/22 is a very small opening.
ISO: A term that digital camera manufacturers borrowed from the film world, to indicate how sensitive the film or digital sensor is to the light that strikes it.
Summary: Shutter speed and lens aperture determine how much light strikes the film or your camera's digital sensor. ISO determines how sensitive the film or digital senor is to that light
Different combinations of shutter speed and aperture can be used to obtain creative results.
Very fast shutter speeds can freeze objects in motion: Think a basketball player in mid-air as s/he drives to the basket or seeing a hummingbird's wings in flight.
Slow shutter speeds will allow moving objects to blur: Think a trail of auto tail-lights at dusk on a busy freeway.
Very small apertures keep everything from the closest object to the furthest in sharp focus: Think a desert landscape with sagauros in the foreground and mountains in the background, all in sharply defined.
Large apertures will let the photographer create portraits or still lifes with selective focus: Think a photo of a single rose. Each petal, each droplet of water on each petal is in sharp focus, but the surrounding leaves are in gentle, slightly blurred soft focus, so as not to detract from the rose.
Sometimes photography instructors use The Old Bathtub Analogy to help students visualize using different shutter speed/aperture combinations:
Imagine a bathtub: To fill it up, you need to open the faucet, and let the water run for a while.
You can open the facucet all the way for a short time, or turn it on to a trickle, and allow the water to run for a long time. Either way, the tub eventually fills up.
Think of the faucet as your aperture setting, how wide you open it is the f-stop.
Think of the length of time you let the water run as the shutter speed.
If you open the faucet wide, the tub will fill in a short period. (Wide aperture/fast shutter speed)
If you open the faucet just a little bit, the tub will take a long time to fill. (Small aperture/slow shutter speed)
Here's a really excellent post on the Photodoto photography blog. (Yes, there are photography blogs and Photodoto is a good one)
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Cheryl.. this is great.. I'm a PHD(push here dummy) camera person.. so this explained a lot of thing I didn't know..