Lesson Plan

Resources → Subject Notes → Information Communication Technology ICT → Notes
Lesson Plan
Grade: Date: 25/02/2026
Subject: Information Communication Technology ICT
Lesson Topic: Know and understand that reducing the file size can be achieved by reducing the image resolution or colour depth
Learning Objective/s:
  • Describe how image resolution and colour depth affect file size.
  • Calculate the approximate file size of an uncompressed image using pixel count and bits per pixel.
  • Demonstrate how to reduce an image’s resolution and colour depth using editing software and evaluate the impact on quality and size.
  • Choose the appropriate reduction method for different image purposes (photographs, icons, web graphics).
Materials Needed:
  • Computer with internet access
  • Image editing software (e.g., GIMP, Photoshop, Paint.NET)
  • Projector or interactive whiteboard
  • Sample images (photograph, logo, icon)
  • Worksheet with calculation exercises
  • Handout summarising key formulas and steps
 Introduction:

Begin with a quick poll: “Which online images load fastest for you?” Connect to prior learning about file size and bandwidth. Explain that today’s success criteria are to predict how resolution and colour depth change file size and to apply editing tools to reduce images appropriately.
Lesson Structure:
  1. Do‑Now (5'): Students estimate file size of a given pixel count and colour depth on a worksheet.
  2. Mini‑lecture (10'): Review resolution, colour depth, and the formula File size = pixels × bits ÷ 8.
  3. Demonstration (15'): Teacher shows how to halve resolution and change colour depth in GIMP, displaying before/after sizes.
  4. Guided Practice (15'): Pairs edit a sample image, record new dimensions, colour depth, and file size; teacher circulates for feedback.
  5. Class Discussion (5'): Groups share which method worked best for their image type and why.
  6. Exit Ticket (5'): Write one rule for choosing resolution vs. colour depth reduction.
Conclusion:

Recap the key relationship between pixels, bits per pixel, and file size, and highlight when each reduction technique is most suitable. Students complete an exit ticket summarising their decision‑making process, and homework is to resize a personal photo for web use and document the steps.