Thursday, 25 September 2008

• "How to's": Understanding ISO

  Getting enough light to your sensor is an ever evolving skill. I still mess and mess with my settings to get it right sometimes. When its right though, usually the results are amazing!
  

  

  This cute couple stopped by my home the night before their wedding to finalize some last minute details. I loved how happy and relaxed they were! On a whim I grabbed my camera and we slipped out into the misty streets for some fun and intimate shots. (You can see more from this shoot HERE.) But this kind of shooting posed some pretty big lighting challenges! I choose this picture to illustrate this post on ISO because, while this shot was one of my favorites, you can still see some of the noise that results when you really pump the ISO as I did for this picture.
  
  ISO:
  When we use film cameras we buy film that have different sensitivities to light. An ISO 100 speed film has low sensitivity to light and is recommended for shooting outdoors in bright sunlight or with the use of flash. An ISO 800 speed film has more light sensitivity. But as anyone whose used ISO 800 speed film knows, you loose some quality. This quality reduction is called "grain" in film terms or when talking about digital images it's called "noise". You can see this in the picture above.
  
  With film they refer to the ISO in terms of "speed" since the camera is able to shoot at a faster speed because the film is more sensitive to light. The same is true with digital cameras. However it's the data sensor and not the film that's sensitivity changes in the digital format so we don't talk about ISO anymore in terms of speed.
  
  SLR cameras, as well as most point and shoot models, have a way to adjust the ISO. This simply tells the sensor to collect more light, or have a higher sensitivity to light. When you adjust the ISO sensitivity you get more light but have to be alert to the same quality issues as with film. If you are seeing a lot of noise and still don't have enough light you probably need to somehow get light from other sources.
  
  Basically, the lower the ISO number the less sensitive the camera is to light. So then the reverse is also true: the higher the ISO number is, the more sensitive the camera is to light. This is illustrated below:
  
  

  
  

  
  We've talked about shutter speed and ISO but without an understanding of how Aperture works you still won't be able to maximize your camera's light collecting capabilities. So next time we'll focus on Aperture because together with ISO and Shutter Speed it helps work to produce well lit photos that truly showcase the subject you are shooting!
  
  Try finding the ISO settings on your camera and adjusting to it's highest setting. Can you see a difference in your indoor photos?
  

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