As soon as you start using your digital camera in ISO mode or with low exposure times you may notice something different. For some reason, your pictures come out looking grainy or have little dots of color. You’ve never had this happen with an SLR. What’s up with that?
What your are experiencing is what is known as noise.
What Causes Noise?
Digital photography noise is caused by the same type of electrical noise that creates crackling on your radio or static on your television. It is created by currents or voltages in an electrical device that is interfering with the process of the device.
In your camera there is an image sensor that is made up of many little light sensors. Light sensors are what takes the light and converts it into electrical charge. When a picture is being made, light hits the sensor, an analog signal is produced, which is converted to a digital image. If, during this time, something messes up the particles creating the analog signal, then noise is produced.
Noise is also indirectly created by weak light. The particles creating the analog signal is weaker when there is less light, so the camera is set for a longer exposure time to collect the weak particles to create a better picture. This creates more time for electrical noise to gather, as well.
How to Avoid and Fix Noise
In general, there is no way to prevent noise 100 percent of the time. There are some ways to lessen noise in the final image, though.
Many cameras now have built-in noise reduction systems. These systems sometimes need to be turned on to work, so check your manual for instructions.
If you already have an image that has noise, you can buy photo manipulation software that is specifically designed to reduce the noise in digital images. Photoshop has come out with one called Imagenomic that repairs an 8 megapixel photo in under 4 seconds.
Knowing that high ISO and long exposure times can cause noise is your best way to combat against it in your photos. Simply try to light your subjects as best you can to avoid these two settings.
