Low light, IR and wide dynamic range

Skills you'll practise

• Explain how a day-and-night camera switches to night mode and what changes in the image
• Choose between 850 nm IR, 940 nm IR, white light and thermal for a night requirement
• Diagnose noisy, blurred, flickering, backlit and foggy images and choose a fix for each
• Explain why night-time noise raises bitrate and calculate the effect on a daily average
• Place cameras and illuminators so the IR beam stays clear of nearby reflective surfaces

Course outline

1. 1.Low light, IR and wide dynamic rangeVideo · 2 min
2. 2.Day-and-night cameras and IR lightLesson · 20 min
3. 3.Exposure, noise, motion and bitrateLesson · 20 min
4. 4.Backlight, WDR and IR reflectionsLesson · 20 min
5. 5.Low light, IR and wide dynamic range: knowledge checkKnowledge check · 21 questions
6. 6.Final exam9 questions · passing it completes the course, so people who already know the material can test out

Sources it draws on

The lessons and questions are written from these references, so learners can go back to the original.

• Axis Communications white paper: IR in surveillance (day-and-night cameras, IR-cut filter, 850 nm and 940 nm, thermal versus IR, IR-corrected lenses)
• Axis Communications white paper: IR reflections in dome cameras
• Axis Communications white paper: Lighting for network video (lux, minimum illumination claims, LED flicker)
• Axis Communications white paper: Global shutter vs rolling shutter (exposure time, motion blur, rolling shutter distortion)
• Axis Communications: Wide dynamic range (multi-exposure WDR, motion, what a dB figure does and doesn't tell you)
• Axis Communications white paper: Bitrate control for IP video (VBR, MBR, CBR, average bitrate, GOP length, night noise)
• Axis Communications white paper: Lenses in surveillance (focal length, field of view, f-number, iris, depth of field, lens and sensor match)