What Is an Image?

What Is an Image?

A digital image is nothing more than a grid of tiny colored squares called pixels. Each pixel stores a color value, and when you put millions of them together, they form a picture. The number of pixels determines the resolution. A 1920 by 1080 image has 1920 pixels across and 1080 pixels down, for a total of over two million pixels. The more pixels you have, the more detail you can capture.

Aspect ratio is the relationship between width and height. A traditional TV is 4:3, which means it is slightly square. Modern widescreen is 16:9, and cinema often uses wider ratios like 2.35:1. When you see black bars on a movie, it is because the aspect ratio of the film does not match your screen. Understanding aspect ratio is important in VFX because you need to make sure your digital elements fit the frame correctly.

Bit depth determines how many colors each pixel can display. An 8-bit image gives you 256 shades per channel, which is about 16 million colors total. That sounds like a lot, but it can cause visible banding in smooth gradients like a sunset sky. A 16-bit image gives 65536 shades per channel, much smoother. 32-bit floating point images go even further by storing values as decimals with a huge range, which is essential for HDR and compositing work.

Color channels are how an image stores color information. A standard RGB image has three channels, red, green, and blue, each storing brightness values for that color. When combined, they produce the full color image. Many VFX formats also include an alpha channel, which stores transparency information. An RGBA image has four channels, with the alpha channel telling compositing software how opaque each pixel is.

Not all images are created equal. A photograph from a camera is a raster image, made of pixels. Vector images, like SVG files, store mathematical shapes instead of pixels and can be scaled infinitely without losing quality. For VFX work, raster images are the standard because they represent real world footage, but you might use vectors for certain graphics elements like titles and motion graphics.