The sensors in digital cameras work by converting photons (light) to electrical current, and then that current is measured and assigned a corresponding value and location. Software on a computer can be used to visualize this data as an image.
Digital images exist as language that describes an image. This is fundamentally different from photography, where light interacts with light-sensitive chemistry and alters it, resulting in a physical artifact left as a record of that interaction. Photography is physical, digital imaging is virtual.
Both digital imaging and photography can be used to make images, but despite this overlap of use, the nature of each medium remains fundamentally different and interesting, and each have unique potential uses and qualities.
The data in digital imaging contains signal and noise, that is, useful data that corresponds to what is being measured (signal), and unrelated data that is generated by other means during the process of measurement (noise). One source of noise is called “dark current”. Digital sensors generate current even while not in use, and this dark current adds to the current introduced during use, leading to distorted data.
Amplification can be used to make images with very low light. However, dark current and noise from other sources are amplified as well, leading to a noisier (but far brighter) image than if an unamplified exposure were made. Amplification allows for a shorter exposure, which means movement is more readily frozen.
In this series, I am using very high amplification (ISO 25,600) to digitally image the dim light of passing cars and other sources that illuminate the walls of my home at night. The high amplification makes visible the noise generated by the sensor, visually revealing the nature of the sensor and its role in imaging the scene.