Tag Archives: shot noise

Photons, Shot Noise and Poisson Processes

Every digital photographer soon discovers that there are three main sources of visible random noise that affect pictures taken in normal conditions: Shot, pixel response non-uniformities (PRNU) and Read noise.[1]

Shot noise (sometimes referred to as Photon Shot Noise or Photon Noise) we learn is ‘inherent in light’; PRNU is per pixel gain variation proportional to light, mainly affecting the brighter portions of our pictures; Read Noise is instead independent of light, introduced by the electronics and visible in the darker shadows.  You can read in this earlier post a little more detail on how they interact.

Read Noise Shot Photon PRNU Photo Resonse Non Uniformity

However, shot noise is omnipresent and arguably the dominant source of visible noise in typical captures.  This article’s objective is to  dig deeper into the sources of Shot Noise that we see in our photographs: is it really ‘inherent in the incoming light’?  What about if the incoming light went through clouds or was reflected by some object at the scene?  And what happens to the character of the noise as light goes through the lens and is turned into photoelectrons by a pixel’s photodiode?

Fish, dear reader, fish and more fish.

Continue reading Photons, Shot Noise and Poisson Processes

Sub LSB Quantization

This article is a little esoteric so one may want to skip it unless one is interested in the underlying mechanisms that cause quantization error as photographic signal and noise approach the darkest levels of acceptable dynamic range in our digital cameras: one least significant bit in the raw data.  We will use our simplified camera model and deal with Poissonian Signal and Gaussian Read Noise separately – then attempt to bring them together.

Continue reading Sub LSB Quantization

SNR Curves and IQ in Digital Cameras

In photography the higher the ratio of Signal to Noise, the less grainy the final image normally looks.  The Signal-to-Noise-ratio SNR is therefore a key component of Image Quality.  Let’s take a closer look at it. Continue reading SNR Curves and IQ in Digital Cameras