ISO

ISO is the third key component of the exposure of a digital photograph. In my opinion, your choices regarding shutter speed and aperture are to be based off of this first decision. Choosing an ISO level is generally my first thought when setting up my initial exposure when I enter an environment because once it's set it's generally not going to be changed unless you go to a dramatically differently lit environment with different shooting needs.

But what is it? Simply put, your ISO is the level of sensitivity your camera's sensor is to light. But just as the other components of exposure there is no "best setting". Every situation will dictate a different set of exposure settings, and this is no difference.

And just like the other pros and cons we've discussed, for example wanting to capture crisp action but choosing too fast of a shutter speed that the image is too dark, ISO too has it's caveats. In a nutshell, a low ISO is going to make the sensor desensitized of the light however it will afford you vivid pictures with rich colors and little to no "noise". A higher ISO setting is going to make your sensor more sensitive to light (allowing you to shoot in darker conditions with a higher f stop and quicker shutter speed) at the expense of those rich colors and also the addition of unsightly digital noise created by the sensor straining for light. It's also safe to say that there is a certain amount of contrast related detail lost as well with these higher ISO settings. The highest ISO settings are generally very ugly a produce horrible photos are quite low light and I advise most people to never to consider using them.

The noise to ISO level ratio is very dependent on the quality of your sensor and you'll see a considerable quality jump with better cameras. All digital cameras regardless of weather they are a DSLR or point and shoot have this setting and lets you tinker with it. Most people with digital point and shoots keep it on auto which allows the camera to set the ISO setting which is for better of for worse. The following examples are from one of my favorite digital photography guru's Ken Rockwell using the model camera that I personally own.

Understandably these are just looking at ISO noise and ISO noise alone. The other components of exposure have been changed to compensate for the changing of ISO so that the pictures exposure remains constant. There are ways to hide and filter out this noise in post processing, again at the expense of detail, that I may discuss in a future post.