- Michael Kohnhorst
Field of View / Rule of Thumb
From 1974 - 1989 I worked as a camera assistant on films, episodic tv shows and commercials. For television we usually shot on 35mm film and the images were composed within an image area known as TV Safe Action. TV Safe Action had an aspect ratio of 4:3 and measured approximately 18mm X 14mm.
We used a simple rule of thumb to determine the distance needed to achieve the field of view for a head and shoulders closeup at any focal length: divide the lens focal length by ten and express the result in feet and inches. For example, 20mm÷10 = 2 feet, 45mm÷10 = 4.5 = 4 feet 6 inches or 135mm÷10 = 13.5 = 13 feet 6 inches. While the image size will vary with the aperture size of a format, within any format this simple formula will give you the same field of view at the point of focus.
We used this mainly to match image size between closeups, but it was also useful for placing the slate so that it could be easily read by the editor. It is also a useful baseline for extrapolation: halve the focal length or double the distance and you get a field of view twice as high and wide. Conversely, double the focal length or halve the distance and you get a field of view that is half as high and wide.
Notes on the illustrations –
I used the Field of View and Preview function on David Eubank’s pCAM Pro to generate these screen grabs. pCAM Pro is the industry standard, a truly indispensable cinematography and photography tool. David has made constant improvements to the interface and ongoing updates to the database since the introduction of pocketCAM for Palm devices in 1999.
Each set of illustrations show the field of view for 25mm @ 2’6”, 50mm @ 5’ and 75mm @ 7’6” for the designated format.
If the illustrations were actual photographic images with foreground and background elements, wide angle and telephoto effects would come into play. Nonetheless, within each format, the field of view at the point of focus is consistent.
The illustrated field of view is the area within the light blue background.
35MM FILM – SDTV TV SAFE ACTION IMAGE AREA – 18MM X 14MM ASPECT RATIO – 4:3 / 1.33:1
LUMIX GH5S IMAGE AREA – 17.3MM X 13MM ASPECT RATIO – 4:3 / 1.33:1
35MM FILM – 1.85:1 PROJECTOR APUTURE IMAGE AREA – 20.95MM X 11.32MM ASPECT RATIO – 1.85:1
LUMIX GH5S IMAGE AREA – 18.8MM X 10.6MM ASPECT RATIO – 16:9/1.78:1
35MM FILM – SUPER 35 IMAGE AREA – 24MM X 13.5MM ASPECT RATIO – 16:9 / 1.78:1
ARRI MINI HD IMAGE AREA – 23.76MM X 13.370MM ASPECT RATIO – 16:9 / 1.78:1
PANASONIC VARICAM 35 IMAGE AREA – 23.04MM X 12.96MM ASPECT RATIO – 16:9 / 1.78:1
CANON 7D MARK II IMAGE AREA – 22.4MM X 12.58MM ASPECT RATIO – 16:9 / 1.78:1
8MM FILM – SUPER 8 IMAGE AREA – 5.7MM X 4.22MM ASPECT RATIO – 4:3 / 1.33:1
35MM FILM – VISTVISION 8 PERF IMAGE AREA – 37.72MM X 24.92MM ASPECT RATIO – 1.51:1
35MM FILM – FULL APERTURE IMAGE AREA – 24.92MM X 18.67MM ASPECT RATIO – 4:3 / 1.33:1
35MM FILM – 2X ANAMORPHIC IMAGE AREA – 42.62MM X 17.78MM ASPECT RATIO – 2.40:1