Pixel. pixels are the basic elements of images. Each pixel is a point in the image and has associated values for the brightness of the colours that make up that pixel (Red,Green,Blue or RGB). Black is (0,0,0) ie no brightness in red, green or blue. White is (255,255,255) ie full brightness in red, green and blue. A mid red pixel might be (128, 0,0) ie partial brightness of red and no green or blue. Bright yellow is (255,255,0) ie equal amounts of red and green, and no blue at all. It’s a bit like mixing paint colours. Each image may be thousands of pixels high and thousands wide. For example an Olympus OMD-EM1 makes images 4608 pixels wide and 3456 pixels high.