Computing KS3/4: How does a digital camera work?

Professor Danielle George explains how a digital camera’s CMOS sensor captures an image, using balls and buckets to represent photons, electrons and capacitors in an interactive demonstration with four children.

The demonstration shows that when a photon of light hits a pixel, the pixel releases an electron, which is stored by the capacitor.

The more light that hits the pixel, the more electrons are released, and so the amount of charge in the capacitor is a measure of how bright that part of the image is.

This measurement from the capacitor is then used to tell the image generator how bright that pixel should be.

The demonstration shows how four children represent four pixels in a large image.

This clip is from The Royal Institute Christmas Lectures 2014.

Teacher Notes

Key Stage 3 and 4:

This could be used to help students understand how images are captured by digital cameras.

Ask students to create a diagram showing how the CMOS sensor captures the image.

Students could be asked to explain if it is always better to have as many pixels as possible.

Curriculum Notes

These clips will be relevant for teaching Computing, ICT and Computer Science at KS3 and GCSE/KS4 in England, Wales and Northern Ireland and 2nd Level and National 4/5 in Scotland.

The topics discussed will support OCR, Edexcel, AQA,WJEC GCSE in GCSE in England and Wales, CCEA GCSE in Northern Ireland and SQA National 4/5 in Scotland.

More from The Royal Institute Christmas Lectures 2014:

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How LED screens work
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How robots can work together in a swarm
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The Mars Rover and autonomous navigation
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Solving a Rubik's cube by smartphone
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What can 3D printing be used for?
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Touching virtual objects
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