A digital image is made up of a 2D array of numbers called a Matrix
Bit depth - A descriptor of the grey scale value attributed to each picture element
Pixels are the smallest component of a matrix

The density of each Pixel ( picture element) has to be a whole number. Each pixel has a bit depth or a number of bits which controls the brightness of the pixel – 4bit, 8 bit, 10 bit or 12 bit

The greater the bit depth the more the precise digitalization of the analogue signal, and the greater the various shades of grey

This is turn improves its contrast resolution - a previous slide suggested that 1024 discrete shades of grey can be displayed - but we should consider actually how shades of grey can the eye distinguish under optimum image display conditions?

It is now established that the human eye can discriminate 'between 700 and 900 simultaneous shades of gray for the available luminance range of current medical displays and in optimal conditions.' It is presently felt that it is of 'no use to simultaneously display more than 10 bits of gray (1,024 gray shades) because this already exceeds the capabilities of the human visual system

Larger the matrix size, greater the number of pixels, better the image quality

	Created by Rutendo Chingomb almost 9 years ago

1 Diagnostic Radiography (Science and Technology) Slide Set on Computed Radiography & Digital Radiography, created by Rutendo Chingomb on 24/12/2015.