This is a Calca document to calculate positions for rulers of a presentation, a video, graphical document, etc. As a video editor I can tell that "TV-safe areas" are a good rule of thumb for presentations, because there's always someone sitting in the back, the projector is never centered, and so forth.

rule of thirds.markdown

Credits

Andreas Zeitler
zCasting 3000
zcasting3000.com

Setup

aspect ratio = 16 / 9 =>
width        = 1920
height       = width / aspect ratio =>

Thirds

column width = 1920 / 3     =>
row height = height / 3     =>

column 1 = column width     =>
column 2 = column width * 2 =>

row 1 = row height          =>
row 2 = row height * 2      =>

Safe Areas

See EBU R 95.

Action-Safe Area

action percent = 5%

left ruler = width * action percent     =>
right ruler = width - left ruler        =>

top ruler = height * action percent     =>
bottom ruler = height - top ruler       =>

Invisible Area

invisible percent = 3.5%

left ruler = width * invisible percent  =>
right ruler = width - left ruler        =>

top ruler = height * invisible percent  =>
bottom ruler = height - top ruler       =>