IOS controls how sensitive the camera sensor is to light.

The higher the ISO number the more sensitive your sensor and the less light is needed in your photo, however this can lead to more noise in the picture. Preferably you would want to keep the IOS as low as possible and change the studio lighting instead if possible or go outside as daylight is always better quality light. However, some photographers use the “noise” created by high ISO to their advantage for artistic purpose to give the image an “old” feel to it or to accentuate the concept meaning behind their image.

You can see here the noise appear in the photo and the quality of the image decrease as more light is let in through IOS. This is why keeping a correct ISO for the environment you’re shooting in.

First I took some images inside the corridor where there was still some natural light. I took a set of seven images each at a different ISO setting but keeping all other settings the same. The first image of the corridor in the blog I took at ISO-800. The second at the highest possible ISO setting on the camera i was using which was ISO-6400 where you can clearly see the “noise” seep into the image as the sensor takes in more light than necessary to create a clear image and instead it ends up with almost a pixelated look.

For the second image I went to the fire exit door to use the bright natural light. I took the images not even a few seconds apart so the lighting outside did not change I also did not change any other setting other than the ISO and the difference is very obvious. This proves that the ISO is what causes the over exposure that forms the “noise”.