A safe area in terms of the frame relates to titles and captions, as well as some graphics. The purpose is to make sure that on a myriad devices and screens those most important details on the image will be seen. This is because different devices and TV screens may cut off differing amounts of the image, especially at the sides.
With the changes in aspect ratio and likelihood that many will still own a 4:3 ratio device that may not be viewed in letterbox, it is important that these viewers (audiences) are not forgotten and left out. Bit pointless finishing your project and creating beautiful titles when all someone can read is “reen ima” instead of “screen image”.
Broadcast outlets will expect that certain guidelines and practices be followed in order to reduce the problems that can be encountered.
Below are two examples of safe caption/title areas, starting with 16:9 and a 4:3 safe area. The pixels on both diagrams denotes how many and when the safe area starts and ends.
For instance the example below (A) states that the horizontal caption/title 4:3 area starts at pixel 337 into the 16:9 image and ends at pixel 1584 of the 16:9 image. On the vertical the title/caption area starts at pixel 55 and ends at pixel 1026 (this is 70% of the frames width and 90% of the frames height).
Pixels are read from top to bottom and left to right, but it doesn’t matter the caption/title safe image area stays the same size and in the same place within the frame.
The following examples are for HDTV screen ratios. Frame size alters with 4K resolution, but the same general visual guides apply.
In the following diagram (B) the main aspect ratio remains 16:9 with the same overall measurements (horizontal pixels 1 to 1920 and vertical pixels 1 to 1080), but the inner title safe area is now a 14:9 aspect ratio safe area. This measures on the 16:9 image as horizontally starting from pixel 298 and ending at pixel 1632, while vertically sharing the same measurement as diagram (A) pixel 55 to pixel 1026 (this is 65% of the frames width and 90% of the frames height).
The middle point of all the areas from the diagrams above (on 16:9 format) are horizontally; pixel 960 and vertically; pixel 540.