What is Depth of Field ?

It's the portion of a scene that appears sharp and in focus.

photography.about.com

Middle swan is sharp and in focus.

Related: Aperture.

Depth of Field	digital-photography-school.com
Small Aperture, large DOF, everything sharp.	Large Aperture, small DOF, background blur.

References:

• http://www.cambridgeincolour.com/tutorials/depth-of-field.htm
• http://en.wikipedia.org/wiki/Depth_of_field
• http://photography.about.com/od/takingpictures/ss/DOF.htm

What is ISO ?

It's the sensitivity setting for the sensor in your camera.

Rated by ISO:

• ISO 100 = less sensitive to light.
• ISO 800 = more sensitive to light.

Related: Aperture, Shutter Speed.

• Low ISO 100 = requires more light, larger aperture, lower shutter speed, less noise in photo.
• High ISO 800 = requires less light, smaller aperture, higher shutter speed, more noise in photo.
  
  

  Noise / Grain Effect	dpstudent.blogspot.com
  Low ISO 100, less noise, less grain.	High ISO 800, more noise, more grain.

In short:

• Go for lowest ISO possible, unless you want the grain effect.

 

References:

• http://www.photoxels.com/tutorial_iso.html
• http://www.dpreview.com/learn/?/key=sensitivity
• http://dpstudent.blogspot.com/2009/05/what-is-iso-setting-on-my-digital.html

What is Shutter Speed ?

It's the amount of time the shutter opens to let light into your camera.

Rated by seconds:

• 1/1000 s = high / fast shutter speed.
• 3 s = low / slow shutter speed.

Related: Aperture, ISO.

• Fast shutter (1/100 s) = requires bigger aperture, small DOF, may require high ISO.
• Slow shutter (3s) = smaller aperture, large DOF, allows low ISO.
  
  

  Motion blur	wikipedia.org
  High shutter speed, freezes action.	Low shutter speed, causes movement blur.
  Night Photography	photoxels.com
  Fast shutter, darker photo, less light.	Slow shutter, brighter photo, more light.

In short:

• Fast shutter speed to freeze action, slow shutter speed for motion blur.
• Slower shutter speed for more light.

 

References:

• http://en.wikipedia.org/wiki/Shutter_speed
• http://digital-photography-school.com/shutter-speed
• http://www.mir.com.my/rb/photography/fototech/apershutter/shutter.htm

What is Aperture ?

It's the size of the hole through which light travels into your camera.

Left to right, small apertures (f/5.6) to big apertures (f/1.8) shown above.

Rated by f-stop:

• f/1.8 or f1.8 = wide opening / big hole / big aperture.
• f/5.6 or f5.6 = small opening / small hole / small aperture.

Related: Depth of Field (DOF), Shutter Speed, ISO.

• low f-stop (f/1.8) = wide aperture, more light, high shutter speed, small DOF, allows low ISO.
• high f-stop (f/5.6) = small aperture, less light, slow shutter speed, large DOF, may require high ISO.
  
  

  Depth of Field	digital-photography-school.com
  Small Aperture, large DOF, everything sharp.	Large Aperture, small DOF, background blur.

In short:

• To blur backgrounds and have a small DOF, lower the f-stop to have a wide Aperture.

 

References:

• http://www.mir.com.my/rb/photography/fototech/apershutter/aperture.htm
• http://www.cambridgeincolour.com/tutorials/camera-lenses.htm
• http://en.wikipedia.org/wiki/Aperture