Aspects & Formats
Film based projects may be shot and finished in various manners. We use the term ‘aspect ratio when speaking of the shape of the image area. The aspect ratio of an image is
the width of the image divided by its height,
expressed as a ratio, such as 1.85:1. Aspect ratios are commonly reffered to by only the first number, for example 1.85 or 1.33.
We refer to the shape of the SD or HD screen as a broadcast format. The broadcast format of SD is 4:3 which corresponds to the 1.33 aspect ratio. The broadcast format of HD is 16:9 which corresponds to the 1.78 aspect ratio.
You will notice we use the term aspect ratio when we speak of the shape of the film frame, and we use the term broadcast format
when we speak of the shape of the
screen. It is important to make this distinction because any aspect ratio can be displayed by any broadcast format using various methods to modify the image if the aspect ratio does not correspond with the broadcast format. The methods for modifying the image to fit the screen are Letterboxing, Pillarboxing, Center Extraction and Anamorphic.
In order to properly display full exposed frame originated with an aspect ratio which is greater than the broadcast format of the screen, mattes are applied to the top and bottom of the screen. These mattes cover the unused image area preserving the original framing. This is used to for any content displayed in the SD broadcast format (4:3) that has an aspect ratio greater than 1:33:1, as wells as for any content displayed in the HD broadcast format (16:9) that has an aspect ratio greater than 1:78:1
In order to properly display the full exposed frame originated with an aspect ratio of less than 1:78:1 in the HD broadcast format (16:9) a matte is applied to the left and right sides of the image.
In order to utilize the full display area the video is sized to fit the top and bottom of the broadcast format and the left and right sides are cropped. If this was not taken into consideration during the shoot a pan & scan pass may be required where corrections are made to reposition the frame.
In order to take advantage of the full resolution available and maintain proper aspect ratio, content originated with an aspect ratio greater than that of the SD broadcast format (4:3) may be vertically squeezed. The image requires processing to be un-squeezed during viewing to display the full frame in with the proper aspect ratio.