Chapter 4. Essentials
Every photograph you take requires processing. This processing can be done in your camera or it can be done on your computer using Phoduit. Doing the processing on your computer lets you take artistic control. In this chapter, you’ll learn about the essentials used to process a typical photograph.
4.1 What is an image
When you take a photo with your camera, it stores the photo as a grid of points called an image. Images can then be manipulated on a computer to look more pleasing and then shared over the internet or printed.
Each point in an image is made up of a set of numbered values called channels that together form a pixel which describes a color. Most cameras produce pixels that are made up of a set of three channels representing the colors red, green, and blue. These three colors are additively mixed together to produce different colors.
The use of red, green, and blue together, as commonly used by cameras, is part of a color model called RGB. A color model is a model that describes how to represent a color. Different mediums often use different color models. For example, most printers use the cyan, magenta, yellow, and black color model called CMYK.
Images in Phoduit have four channels and are usually in the RGBA color model. RGBA is very similar to RGB except it also has an alpha channel. The alpha channel controls the transparency of an image which is useful for merging multiple images together.
To work with pixels on a computer, each channel is represented as a number. These numbers are stored as bits. The number of bits is called the bit depth. Using more bits means more shades of colors. Most computer displays work with pixels that have a bit depth of 8 bits or numbers in the range from 0 to 255. Cameras often produce pixels with a bit depth of 12 bits (ranging from 0 to 4096) or a bit depth of 14 bits (ranging from 0 to 16384) but are processed and stored at a bit depth of 8 bits unless saved in a raw format. You’ll learn about raw images in Chapter 7. Raw Images.
Phoduit converts all images to a bit depth of 16 bits (ranging from 0 to 65535). By using a larger bit depth than can be displayed on a typical computer display, you give yourself much more editing latitude. Even a small amount of editing on images with a smaller bit depths can cause color gradients to turn into solid color strips called banding. Images converted from a lower bit depth do not magically gain more detail but they can still take advantage of the higher bits per channel during editing to limit banding.
Phoduit processes images using nodes. Different nodes perform different changes to an image. Nodes are connected together, forming a graph, to produce more complicated effects and ultimately make your photos more unique. Graphs are typically laid out to flow from left-to-right because nodes use connections on their left as input and connections on their right as output.