In this article we want to share with you what we know about Noise, the dreaded splatter on an otherwise beautiful image. We believe that the most efficient way to reduce noise in your photography is to first understand it. I believe the famous quote is ‘know your enemy’.

What is Noise?
Noise is to a photograph what dust is to a clean mirror. You can see the image, but it is clouded by tiny dots that make otherwise smooth surfaces uneven and scratchy. You are able to see the dots that make up the image as opposed to a smooth image. (it makes me think of pointillism)

The same image with and without Noise

The same image with and without Noise

While the term ‘digital’ lends itself to a high quality, you need to keep in mind that even your digital camera uses an analogue component to read the light. Your CMOS Image Sensor (or CCD) is that component.

Your Image Sensor
On your image sensor there are a number of tiny squares, each of these squares is a photosite and each photosite has one tiny light sensor on it. Each photosite corresponds with one pixel in your image.

What happens when you take a picture?
When you take a picture, light will touch your image sensor (the photosites) and photo-electrons are made. These photo-electrons charge up your analogue signals and then your A/D Converter (Analogue to Digital Converter) changes those analogue signals into digital ones so that your camera can read them in a format that it understands.

So where does Noise come from?
Noise can be a result of a few different things. For example, Dark Current, this is noise generated by thermal electrons (heat) that interfere with the photo-electrons when you are taking your picture. The thermal-electrons unbalance the photoelectrons and the wrong signal is sent when converting from analogue to digital.

Noise is also cause (and this is most probably the most common form of noise) when you have your ISO set too high. The higher the ISO the more noise you will receive as you are increasing the signal to the photosites. The stronger signal opens itself up to receive more electric noise as well.

When you have your ISO set high for very low light photography you are actually telling you camera to collect more light by leaving the shutter open for a longer period of time and therefore risk not only collecting more light, but also collecting more noise. (like leaving the window open for a while to let in a cool breeze, but having to also deal with the smell of the neighbours compost heap, the longer the window is open, the cooler the room, but the worse the smell!)

To make things more complicated, each photosite also creates electrical noise which will interfere with its neighbouring photosite. Camera manufacturers have countered this problem by placing photosites further apart and lessening the interference. You can also purchase a camera with a larger image sensor (which can hold larger photosites). The larger photosites have a larger space with which to collect light and are able to make a better light to noise ratio.

For this reason it is important to note the amount of pixels the camera has and what space it is put into, for example:
Let us look at two cameras.
Camera 1 is an 18 megapixel camera and Camera 2 is a 12,3 megapixel camera. Can you automatically assume that Camera 1 is the better camera? Not until you have also looked at the size of the image sensor! Perhaps Camera 1 and Camera 2 have the same size image sensor? If that were the case then Camera 1 would have photosites that are much closer together than Camera 2.

Camera 1 has a 22.3 x 14.9 mm CMOS sensor.
Camera 2 has a 23.6 x 15.8 mm CMOS sensor

For the sake of explanation - that is a scored point for Camera 2, with a larger sensor and fewer photosites. Of course in this case the difference in sensor size in minimal and you need to take into consideration what in-camera options each model has to combat noise reduction.

To put the idea in its basic form, if you are tossing between purchasing two cameras that are on ‘equal footing’ with what they are offering, go for the one with the larger image sensor.

How can you avoid Noise in your photography?
Here are a few things that you need to keep in mind when taking photos.

Setting you camera on a long exposure will give more time for noise to enter your picture, try keep your exposure times to a minimum, you can make up for the loss of light in you exposure setting by adjusting your aperture. You will need to play with this to find what suites your camera best.

As an example though, set your camera to 1/500 at f/2.8 and take a photo…then set it to 1/60 at f/8 and take the same photo. You will notice that the lighting doesn’t change much in between the two images but you have managed to set your camera at a lower exposure and therefore have lessened the likely hood of noise in your image. Like I said before, it is something that you need to play with and depends on the lighting situation and your camera.

A higher ISO will also result in more noise, try and use your flash rather than setting your ISO too high in low light conditions. Where ever possible, the flash will create much clearer images than a higher ISO setting.

If you do need to set your camera to a long exposure due to poor lighting, use a tripod or set the camera down somewhere where there will be no movement during image capture.