aspect ratio

For images such as photographs, this is the ratio between the width and height of the image. For example a square image has an aspect ratio of 1:1 whereas the aspect ratio of a traditional photograph is 4:3, that is a 1/3 wider than it is high. For a digital image the aspect ratio usually refers to the ratio of the number of pixels, for example a 1024x768 has a 4:3 aspect ration, whereas a wide screen at 1920x1080 has an aspect ratio of 16:9. Most commoly each pixel is square, and this is certainly the case on almost all computer screens, but occasionally in specialised applications individual pixels may be rectangular and have an individual aspect ratio that is not 1:1; when this is the case the aspect ratio of the overall image and the pixel ratios would not be the same, for example a 1000x500 image where each pixel had a 3:2 aspect ratio would have an overall aspect ratio of 3:1 when printed/viewed.