Like we said on a previous post, every camera has a sensor, which is what absorbs the light and creates the finaly picture you see.
Now the ISO controls the sensitivity of that sensor to light! Meaning that, by increasing the sensitivity, the sensor will absorb more light! Simple right?!
Now lets dig into that for a bit, what do you say?!
I am sure that at some point you tried to shoot something in low light conditions!
And I am sure that when you got back home you noticed something that looked like the second picture. Am I right?!
That is what we call noise!
It is quite annoying, trust me i know. We won't talk more about noise here for now, but we will see the realtion that it has with ISO.
In simple terms, the higher the ISO, the higher the noise!
So, you will get more light at the expense of more noise.
Also, what ISO affects is the dynamic range, higher ISO give you lower dynamic range, making colors apear weird.
If you notice the second picture with the high iso, you will see that is not black. That is because of the lower dynamic range due to high ISO.
Modern day cameras are performing really well though, in terms of ISO performance. We are gonna talk about the characteristics of a camera and various buying advices later on. For now lets stick to the basics.
So you want your ISO number to be at 100 (which is the base value for most models), at all times. That will ensure that you will not have any noticeable noise in your pictures.
Now when the light conditions are not ideal, and you want that extra boost of brightness, sure, increase your ISO. My experience says that even entry level cameras, can handle ISO values up to 800 and produce stunning photos! Full frame cameras and more professional grade equipement, can go up to 6400ISO and produce images that you can print and hang in your wall, with no notice of any noise.
So don't be afraid of a little noise. You can always fix it with some noise reduction in post prossecing.
the higher the ISO, the more the light, the higher the noise in your picture!