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The word 'noise' might be something that you might think is applicable to videos and the quality of their sound, however, it is actually a term that is very much part and parcel of photographic vocabulary.
Indeed, noise is something that can either be a help or a hindrance to photographers depending on what images they are trying to create.
What is Noise in Photography?
If you were making a sound recording of any kind, and on playback, there was a lot of distortion and disruption to the sound, such as crackles, hisses, and pops you would quite rightly say there was a lot of 'noise' on the recording. Well, the same principle applies when a digital photograph has a lot of 'noise.'
Obviously, a photograph does not have audible noise, but the visual noise can take the form of graining, specks, discolored pixels, and general degradation of the quality of the image.
In most cases, this will be regarded as a negative, albeit there are some circumstances where a photographer may want to increase the noise in an image to produce a particular effect.
What Causes Noise in Photography?
Noise can be caused in several ways, and in most cases, it will be one or several settings that the photographer has selected on their camera and lens. The scene in which the photograph is being taken will also play a part, but this again is linked to what settings have been chosen.
It is how these settings influence the image that is captured by a digital camera's 'Charged Couple Device,' or as it is more commonly known, the CCD.
The CCD is what 'captures' the image, so anything which influences that positively or negatively in terms of noise is going to play a big part.
Most Common Causes of Noise on a Digital Photograph
Slow Shutter Speed
This is often selected when light levels are low, and when this is the case, the CCD has more light in each pixel of the image due to the shutter being open for longer. This increased accumulation of light in each pixel translates as noise in the image.
Low Light Scenes
Regardless of the shutter speed, low light scenes are liable to create noise. One of the principles behind this is that the very low light intensity has a natural level of noise equivalent to which exists in the CCD anyway, and this makes pixels appear as noise as they match that of the low light.
High ISO Settings
An ISO setting adjusts the sensitivity level of the CCD in a digital camera. In the days when film was prevalent, you might have heard it referred to as the level of exposure on the film.
While the ISO is set at high, it allows a greater amount of light, and this, in turn, magnifies other elements of the image, such as heat sources.
This can cause a degree of distortion as the light is amplified, in much the same way the sound from a speaker may become distorted if the volume is turned up too high.
Ways to Avoid or Reduce Noise in Photography
Reduce the ISO
Obviously, there will be scenarios where you may still want to keep the ISO high to allow the correct exposure, but you should try to set it as low as you can in order to reduce noise.
If exposure conditions allow, the improvement in detail and clarity that is possible if you reduce ISO from 16000 to 4,000, is very noticeable.
Reduce the Shutter Speed
This will simply reduce the possibility of unwanted image signals getting mixed in with the ones that you want in your photographs such as brightness, contrast, and color.
Capture Images in the Optimum Exposure Conditions
One simple way to negate the need for shutter speeds and ISOs having to be adjusted in such a way that they cause noise is to capture your images when all the correct conditions are present.
Light levels, shadows, and the background all influence the exposure settings on your camera, and if these are optimized, then there is less need for settings that generate noise in your images.
Upgrade Your Camera
This might seem too obvious, but what we mean here is to use a camera with a larger sensor.
This may be the only option if no matter what steps you try to reduce noise, they simply do not give the improvements in image quality you are looking for.
A larger CCD will be capable of capturing more information from every image and thus provide greater scope for you to make other adjustments to reduce noise.