ถามด้วยความไม่รู้ครับ มันต่างกันยังไงหรอครับ 16:9 กับ 4:3 เนี่ย  อยากรู้มานานแล้ว 
http://en.wikipedia.org/wiki/Aspect_ratio_(image)The aspect ratio of an image is its displayed width divided by its height (usually expressed as "x:y"). For instance, the aspect ratio of a traditional television screen is 4:3, or 1.33:1. High definition television uses an aspect of 16:9, or about 1.78:1. Aspect ratios of 2.39:1 (2.35:1 prior to SMPTE revision in 1970) or 1.85:1 are frequently used in cinematography, while the aspect ratio of a sync-sound 35 mm film frame is around 1.37:1 (also known as "Academy" ratio). Silent films which used the full frame were shot in 1.33:1.
The evolution of film and TV aspect ratios
The 4:3 ratio for standard television has been in use since television's origins and many computer monitors use the same aspect ratio. Since 4:3 is the aspect ratio of the usable frame within the Academy format once the soundtrack had been taken into account, films could be satisfactorily viewed on TV in the early days of the medium. When cinema attendance dropped, Hollywood created widescreen aspect ratios to immerse the viewer in a more realistic experience and, possibly, to make broadcast films less enjoyable if watched on a regular TV set.
16:9 is the international standard format of HDTV as used in Australia, Japan and America, as well as in Europe on satellite and non-HD widescreen television (EDTV) PAL-plus. Japan's Hi-Vision originally started with a 5:3 ratio but converted when the international standards group introduced a wider ratio of 5⅓ to 3 (=16:9). Many digital video cameras have the capability to record in 16:9. Anamorphic DVD transfers store the information in 16:9 vertically stretched to 4:3; if the TV can handle an anamorphic image the signal will be de-anamorphosed by the TV to 16:9. If not, the DVD player will unstretch the image and add letterboxing before sending the image to the TV. Wider ratios such as 1.85:1 and 2.39:1 are accommodated within the 16:9 DVD frame by adding some additional masking within the image itself..................
ลองอ่านต่อเองนะครับ .... เค๊ามีภาพประกอบด้วย .... สรุปย่อๆ ก้อคือ  อัตราส่วน ระหว่าง  ความกว้าง กะ ความสูง ของภาพ ..... เช่นจอทีวี หรือ จอ คอมพิวเตอร์ แบบ ปกติ จะเป็น  กว้าง 4 ส่วน สูง 3 ส่วน = 4:3 หรือ 1.33:1  ....... ในขณะที่จอแบบ widescreen จะเป็น แบบ กว้าง 16 ส่วน สูง 9 ส่วน = 16:9 หรือ  1.78:1 .....  
