Sizu Riatto
Every Angle · Chapter 7

The Camera Triangle

A camera on a wall makes a right triangle with the ground. Tan turns its height and tilt into the blind patch underneath and the strip it really watches.

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Opens on the book's house and plot. Change any number to your own and press Calculate.

The camera on the wall

A face, and the pixels (for the look-down angle at the identify reach)

Enter the height, tilt and vertical field of view, then press Calculate.

The formula

  • The lower edge of the picture is tilt + vertical view ÷ 2 below the horizontal; the upper edge tilt − vertical view ÷ 2
  • The near blind spot = height ÷ tan(lower edge angle): nothing nearer reaches the picture at ground level
  • The center of the picture meets the ground at height ÷ tan(tilt)
  • A face at height f first enters the bottom of the picture at (height − f) ÷ tan(lower edge angle)
  • If the upper edge is at or above the horizontal, the view runs to the horizon; else it meets the ground at height ÷ tan(upper edge)
  • Looking down on a face at distance d: tan⁻¹((height − f) ÷ d)
The book's worked example, Chapter 7. Mounted at 2.7 m (8.9 ft), tilted 20° down, 53° tall: the lower edge is 46.5° below horizontal, so the near blind spot is 2.56 m (8.4 ft). The upper edge is 6.5° above horizontal: the view runs to the horizon. The center of the picture meets the ground 7.42 m out; a 1.6 m face enters the picture 1.04 m out; at the identify reach the camera looks down on a face at 14.4°.
Check it. Tape a mark on the ground at the blind-spot distance and walk toward the camera on the recording: your feet should leave the bottom of the picture at the mark.

Honest limits. A flat ground and a camera level side to side are assumed; slopes move every distance. Steep look-down angles show the top of a head, not a face: lower and further back is often better than higher. The book's house was worked out on paper from published figures, not surveyed by us: measure your own, and walk your own plot at night. Prices are illustrative US prices from November 2026, shown without a currency sign; put in your own. Everything stays in your browser: no sign-up, nothing stored.

These calculators go with Every Angle (Make It Add Up, Book 2), where every number on this page is worked by hand.