Sensitivity (ISO)

Your DSLR has different ISO settings for you to chose from. Some cameras start at 50, most at 100 and others at 200 and go up to different amounts. For example, the Canon 450D (Rebel XSi) has an ISO range of 100-1600 whereas the much newer Canon 550D (Rebel T2i) and the 600D (Rebel T3i) have an ISO range of 100-12800. Your camera will allow you to chose an ISO setting between that range.

So what does it do? It basically makes your pictures brighter. The higher the ISO number, the brighter the picture will be. But it comes at a cost. While the picture will be brighter, it will also be grainier. So a picture taken at ISO 800 will have more grain than a picture taken at ISO 200. The grain added by ISO is called "noise".

Generally you want to take pictures with less noise in it, but sometimes you do not have enough light for a properly lit picture. In that case, it is better to turn up the ISO and get the shot.

Different cameras react differently to the same ISO setting. The newer cameras with newer sensors will generate less noise than older cameras with older sensors at similar ISO. So the Canon 600D (Rebel T3i) will have less noise at ISO 1600 than the Canon 450D (Rebel XSi) at the same ISO.

And as usual, I have examples for you guys. I put my camera in the manual mode, set my aperture at f/4, my shutter speed at 1/40th of a second and took pictures from ISO 200 to ISO 6400.

ISO 200

ISO 400

ISO 800

ISO 1600

 ISO 3200

ISO 6400

 

So as you can see, the pictures got a lot brighter with the high ISO setting but they also got noisier. It is better to have the camera at a low ISO setting in daylight or when you have enough light available, but you will have to crank it up at night or indoors to get a properly lit shot.

ISO is like steroids, it enhances your performance but also comes with side effects. The side effect being noise.

Play around with the ISO in your camera and check out the different results you get. Next time I will talk about how to get a proper exposure but different results by using Aperture, Shutter speed and ISO. 

Feel free to ask any questions that you may have.