ISO/F Stop /Shutter Speed

ISO = the level of sensitivity to light

Like film, the higher the ISO number, the less light is needed to achieve the correct exposure.

100, 200, 400, 800, 1600 are a typical range for most cameras.

As ISO is increased in digital photography, noise often results in the darker tones (ie the shadow areas).

Longer exposures of a second or more can also create noise patterns.

F Stop / Aperture

The aperture is like the iris in our eye, the wider it is open the more light is allowed in.

Depth of field is how much is in focus.

f 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32 are aperture steps (aka F stops).

Each step is half as much light as the numbers increase (f 4 let's in half as much light as f 2.8)

Each stop is twice as much light as you move from an f stop to the next lower number (f 2.8 is twice as much light as f4)

Aperture controls depth of field, the smaller the f stop number, the wider the f stop opening, the smaller the depth of field. So f 4 will give less depth of field that f 8.

The larger the number, the smaller the aperture, the more that is in focus.

For example: with f 2.8 set, the eyes are sharp, and the ears are out of focus.

The same shot at f 8 set, the eyes, ears, and wall behind are all in focus.

A wider aperture (e.g. f 2) can be very useful in a low light situation.

A smaller aperture (e.g. f 11)can be useful for shooting a large group.

Shutter Speed

The shutter speed controls how long the shutter is open.

A typical range might be:

<-----1 second, 1/2second, 1/4,1/8, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500, 1/1000----->

The shutter speed doubles as you move higher and halves as you move to lower numbers:

1/1000 is twice as fast as 1/500 and 1/500 will stay open twice as long as 1/1000

Longer shutter speeds are necessary for lower light situations, and higher speeds are needed in brighter situations.

Slower shutter speeds can be harder to hand hold, causing lack of sharpness due to camera shake.

A tripod may be necessary at longer shutter speeds.

Faster shutter speeds can freeze action, but require light more.

Tony Wood is a photographer in the Philadelphia area.

http://www.learnphotographybasics.com

http://www.anthonywoodphotography.com

http://www.flickr.com/photos/the_chocolate_trio/