The pixel is the smallest component that makes up a digital picture. Millions of them arranged in a tight grid make up the electronic display. Each is powered at a certain level representing the brightness of part of the image they are displaying. However the pixel itself is actually made up of three smaller colour elements. A Red element, a Green element and a Blue element (RGB). The colour of a pixel never changes, only the intensity of each colour element. Human eyes cannot resolved such small elements in very close proximity to each other, so we think we are seeing a colour change as the intensity of each colour element of a single pixel changes. Technology has evolved providing 256 luminance values for each colour element of a pixel. This ties in with standards in chip development and the fact that 256 intensity levels are beyond human resolution so there is no need to increase this level any further. The following illustration provides a summary to this article.
The following chart shows how digital electronic chips count in binary using a four bit (4 pin) chip that can give up to 16 output combinations (the reason hexadecimal is used so much in electronics). A voltage at a pin being 1, no voltage being 0: Output combinations are of 1’s and 0’s (binary code). Programs using various algorithms can convert this binary code into electronic control actions. During digital image editing the algorithms of Photoshop will intercept pixel data and alter it as the program instructs. The new data will be saved to the image file for the next image viewer to read.
The illustration below shows a very basic flow from a digital camera to a display. All pixel data is stored in the image file. However some file types like Photoshop’s .psd files also hold extra layer and vector algorithm data that allows manipulation of data that drives displays without altering the original raw pixel data so it can be easily removed during editing if no longer desired leaving the original image data. If the new alterations are desired they can be saved as the new raw pixel data overwriting the original data (Flattening layers). When these image files are copied to other file types like .jpg, they must have all the extra layer and vector data removed first.