Mumbai university > Electronics and telecommunication Engineering > Sem 6 > Television Engineering

Marks: 05

Years: May 2016

Width to height ratio of a picture frame is called aspect ratio.

Width is kept longer than height because of the following facts:

1. Horizontal dimension of a scene is generally more than its vertical dimension.

2. Eyes can move with more ease and comfort in the horizontal plane than in the vertical.

3. The fovea, the surface of maximum sensitivity and resolution at the centre of the retina in the eye has greater width than height. Hence, the longer width of the image ensures more efficient use of the fovea.

4. As a result of intensive subjective tests by cinema professionals, aspect ratio of 4:3 was found to be most pleasing aesthetically and less fatiguing to the eyes. The same ratio was accepted by television engineers as cinema films formed a major part of TV programmes. This enabled direct transmission of films without wastage of any film area.

Thus for conventional TV screens, the aspect ratio is 4:3 in all TV systems. Proportional size of the objects will not change with change in size of the screen so long as the aspect ratio remains the same.

Dimensions of a TV receiver are specified by the diagonal length of the screen. When width is 4x and height 3x, diagonal would be 5x (Pythagoras theorem). Thus, the diagonal will give the value of x.