Guides · Guide 05
How to show a camera's angle of view on a floor plan
A camera on a floor plan is a dot until you give it a lens. Draw the angle of view as a cone and you can see, at a desk, what is in shot, where a light stand will be seen, and where an actor walks out of frame.
The one formula you need
The horizontal angle of view depends on two things: the focal length of the lens and the width of the sensor. For a lens of focal length f on a sensor of width w, the angle is:
angle = 2 × arctan( w ÷ (2 × f) )
You do not need to do this by hand. It is useful to know because it shows why the same lens gives a different picture on a different camera. A wider sensor sees more with the same lens.
Common angles
These are horizontal angles in degrees, worked out from the formula, for the sensor widths ShotPlots uses.
| Lens | Super 35 | Full Frame | Micro Four Thirds | Super 16 |
|---|---|---|---|---|
| 18 mm | 69.3 | 90.0 | 51.3 | 38.4 |
| 24 mm | 54.8 | 73.7 | 39.6 | 29.2 |
| 28 mm | 47.9 | 65.5 | 34.3 | 25.2 |
| 35 mm | 39.1 | 54.4 | 27.8 | 20.3 |
| 50 mm | 28.0 | 39.6 | 19.6 | 14.3 |
| 85 mm | 16.7 | 23.9 | 11.6 | 8.4 |
The sensor widths behind the table are 24.89 mm for Super 35, 36 mm for Full Frame, 17.3 mm for Micro Four Thirds and 12.52 mm for Super 16. Check your own camera's recording area, because cropped modes and anamorphic lenses change the answer.
How wide is the frame at a given distance?
The angle is useful for drawing. For planning a shot, a second rule is faster:
frame width = distance × sensor width ÷ focal length
On Super 35 with a 35 mm lens, an actor standing 3 m from the camera has a frame about 2.1 m wide around them. At 5 m the frame is about 3.6 m wide. That is enough to tell you whether two actors side by side will both fit, before anyone has picked up a camera.
Drawing the cone
1. Put the camera where the lens will be
Place the dot at the camera position, and give it a facing. On a floor plan the camera is usually a symbol with a point or a lens end so the direction is clear.
2. Draw two lines at half the angle either side
For a 39 degree angle, each edge sits about 19.5 degrees from the centre line. Draw them out as far as the room or the action goes. Anything between those lines is in shot, give or take the vertical limits.
3. Label it with the lens
Write the focal length on the cone, such as "35mm". The next person who reads the plot needs the lens more than they need the angle, because the lens is what the camera team will actually put on.
What the plan cannot tell you
A floor plan is a view from above, so the cone shows the horizontal limits only. Camera height and tilt decide what the top and bottom of the frame contain. A ceiling-mounted light is out of shot on a flat lens at head height and in shot on a low angle looking up. Write the camera height beside the camera so nobody guesses.
Checking the plot against the cone
Once the cone is on the page, go round every unit and prop. Any light stand inside the cone is in shot unless it is higher than the frame, so it either moves, flies, or gets hidden. This check catches the most common reason a plot has to be redrawn on location, and it costs nothing at a desk.
In ShotPlots you pick the lens and the sensor and the cone matches. Swap 35 mm for 24 mm and it opens up. The focal length prints beside the cone on the PDF. Draw one free, no account, nothing to install, or see a finished sheet and its PDF.
Related
How to make a floor plan for a short film, and How to make a blocking diagram.