Image quality criteria can be divided into two categories: basic criteria that apply to all imaging system, image defects-some of this are unique to television images.
- Image definition. Definition is the degree of 'in-focus' appearance of the image. It is primarily determined by the shape of the transitions between dark and light areas of the picture. (EIA standard resolution test chart)
- Limiting resolution. (?)
- Gray scale. It can be specified by three parameters: 1. highlight brightness, the brightness of the brightest areas of the image; 2. contrast ratio, the ration of the brightness of the brightest areas of the image to the darkest; 3. gamma, the slope of the transfer characteristic of image brightness as a function of scene brightness.
- Flicker: when the frame rate is not high enough to cause the eye to see continuous image.
- Aliasing: sampling problem.
- Geometric distortion.
- Hum: ex. a horizontal hum bar moves vertically through the picture, interference caused by power source voltage.
- Ghost: a duplicate of the main mage, slightly displace from it.
Image quality factors:
- sharpness: how to measure-use a bar pattern, use 'rise distance', the distance for the pixel level to go from 10% to 90% of its final value.
- color accuracy
- tonal response & contrast
- exposure accuracy
- lens distortion: r_u = r_d + kr_d^3