Definitions of image noise vary from source to source. What image noise does universally mean, however, and what its types are, is what this piece is all about.

What is Image Noise?

Image noise is a phenomenon no photographer can afford to ignore. Left alone, image noise can create problems, but several cameras, especially those of the digital variety, come with inbuilt features and settings that help decrease this noise. Then there is always the option of image editing which helps modify the noise levels. However, since this may not always work, it is best not to let perfectly good pictures be wasted byan image noiseproblem. This can be done by taking every available preventive measure to reduce the noise before images go to the editing level. Simply put, image noise is to digital cameras, what film grains are to analogue cameras. Yet another simple comparison can be made with the slight hissing sound audible from your audio system at full volume.  In digital images, this noise translates into non-uniform specks on an otherwise smooth surface, thereby degrading image quality to a great extent. Incidence of noise is also directly proportionate to the sensitivity setting in the camera, duration of exposure, temperature, and varies between different camera models. More specifically, image noise occurs when the sensor and circuitry of a scanner or digital camera produces random variation of brightness or color information in images. It is a phenomenon also seen to develop in film grain and in the inevitable shot noise of an ideal photon detector. Image noise is an unavoidable side-effect occurring as a result of image capture, more simply understood as inaudible, yet inevitable fluctuations. In a digital camera, if the light which enters the lens misaligns with the sensors, it will create image noise. Even if noise is not so obviously visible in a picture, some kind of image noise is bound to exist. Every type of electronic device receives and transmits some noise and sends it on to what it is creating, no matter how you try to prevent it.

Image Noise is generally of the following types:
  • Amplifier noise (Gaussian noise)
  • Salt-and-pepper noise
  • Shot noise
  • Quantization noise (uniform noise)
  • Film grain
  • Non-isotropic noise
However, Image Noise in Digital Cameras is mainly:
  • Random Noise: Random Noise is defined by intensity and color fluctuations above and below the actual image intensity.
  • Fixed Pattern Noise: Fixed Pattern Noise is characterized by “hot pixels”, which is when a pixel’s intensity far surpasses that of the ambient random noise fluctuations
  • Banding Noise: Banding Noise is camera specific. It occurs when a camera reads data from the digital sensor.
While you cannot completely do away with image noise, you can certainly reduce some of it. You can start by using a natural light source and by avoiding taking pictures at night, as they need longer exposure times or high ISO speeds. Use a flash to reduce noise under circumstances where natural light isn’t available. Corrective filters are another device that helps reduce image noise.

How to Cite

Related Articles

More from