The introduction of high definition television super-sized our television sets from the square look of the 4:3 aspect ratio, to the widescreen 16:9 ratio. If you acquire your content in HD, the natural instinct when shooting HD is to use the entire 16:9 frame for composing your shots.
Not so fast.
Currently, most television networks in US markets do broadcast in HD. However, since there are still a significant amount of 4:3 television sets still in use, every one of these HD stations also simultaneously feeds SD signals of their content to their SD viewers. In fact, the majority of the US viewership is actually watching in SD. This means your cinematic 16:9 content is being down-converted to the 4:3 screen ratio for SD viewers.
For more on down conversion methods, please visit our blog post on Being Mindful of Broadcast Down Conversion.
If your final program is heading to broadcast on television, it is important to know how your content may actually be seen by your audience (both HD and SD) and how you can prepare your final cut so that it is optimized and looks the best in both formats.
In order to be eligible for this often-requisite method of down-conversion, your picture (and graphics) need to be center-cut safe.
Creating center-cut safe content starts with proper framing of your talent during production and correct location for your graphics in post. Follow these simple steps to create content that can handle the inevitable down-conversion of your HD content.
"4:3 Safe" is when you center all critical content into the center 70% of the HD screen width. This will accommodate for the center-cutting of the 16:9 image to the 4:3 full-screen aspect ratio during the required down-conversion of an HD signal when distributing to an SD set-top box or television.
Why is this important? Old tube (CRT) televisions were designed with significant over-scan built-in (5-10%) to hide a variety of picture imperfections due to design, manufacturing, and technology limitations. As these sets aged a variety of other mechanical issues would cause the scanning area to change or grow. The rule of thumb is still to accommodate for the lowest common denominator, which in this case is the tube television.
A clean, professional-looking image is displayed properly across all broadcast outlets.