ISO ISO or international index standard is the gage in which our digital cameras allow us to increase the sensitivity of the sensor itself. By increasing the ISO which typically ranges from around 80 to 1600 on compacts and entry level cameras. By increasing the ISO you are increasing the sensitivity of the sensor in your camera towards light. This enables us to take pictures in low light situations. However this comes at a cost, by increasing the ISO setting you run the risk of creating noise. Noise in photography terms is often not a good thing to have. Though when applied in a controlled and creative context can create some great effects, think of it like blur. Blur is only useful if it is managed and applied to the specific areas Noise is the same but unlike blur it is created by the sensor |
 | The sensor within a camera works by collecting light particles called photons. Imaging a large open space and on the ground there are thirty buckets by thirty buckets. This would mean that their are 900 buckets in a square - this is our sensor. if we did this experiment during the day we could clearly see the bottoms of the buckets, this is because they are full of light. For the sake of this experiment we are using red buckets. Now imaging the experiment done in low light, the bottoms of the buckets will become harder to see because the buckets are only half full of light. Depending on where the sun is some buckets might on be a third full. As it gets darker the buckets become more and more empty of light until one bucket has no light in it at all. What happens now? although we know that the buckets are red and therefore we can guess that the bottoms will be red too. A camera does not know what colour the light should be so it guesses. |
As you can see in the diagram above the pixels are multicoloured this is because the sensor has tried to guess what the colours of the buckets should be to suit the image. Some buckets will be full of protons and this is why the image can be made out to be a castle. However many buckets are empty and the sensor is having to fill them with a random colour that it thinks is best suited using the buckets that are full as a guide. As you can see the sensors often get it completely wrong.
Why not use a longer exposure I can hear you cry! This is a possibility but in order to achieve great exposures in low light ie at night you are going to need an exposure of at least three of four minuets. Should you need to take a shot in low light conditions do think about the ISO setting it is very handy in such situations but be sure to run a few trial shots so that you don't over do it.
Bracketing may also help towards low light conditions - this process can be setup through the options of your camera depending on the model. Bracketing allows you to take three shots each one at a different exposure allowing to then merge all three to create a near perfect exposed image.
