Projector Brightness & Throw

Lumens needed to reach the target screen luminance over the whole image area, after screen gain and the ambient light the image must overcome.

Use cases

• Passive viewing 7:1 contrast target
• Basic decision making 15:1
• Analytical decision making 50:1
• Full motion video 80:1

Formula

Lumens = (target luminance × screen area × π) ÷ screen gain

SMPTE EG-18 — 16 fL for cinema

Throw ratio is the manufacturer’s relationship between distance and image width. Screen gain trades brightness against viewing angle, and an ambient-light-rejecting screen buys contrast at the cost of off-axis uniformity.

Use cases

• 0.3 – 0.5 ultra short throw
• 0.5 – 1.0 short throw
• 1.0 – 2.0 standard throw
• 2.0 and above long throw

Formula

Throw distance = throw ratio × screen width

Matte white gain 1.0