Lesson Plan

• Describe the concept of image contrast and its effect on visual appearance.
• Explain how the contrast factor modifies pixel values using the formula p' = 128 + c × (p − 128).
• Demonstrate how to adjust contrast in common image‑editing software while avoiding clipping.
• Evaluate the adjusted image to ensure details are retained and save it in an appropriate format.

• Projector and screen
• Computers with image‑editing software (e.g., GIMP, Photoshop, Paint)
• Sample images for editing
• Worksheet containing the contrast formula and checklist
• Handout of step‑by‑step instructions
• USB drives or cloud folder for saving original and edited files

Begin with a brief discussion on why clear, vivid images are essential in presentations and digital portfolios. Recall the previous lesson on adjusting brightness and ask students how contrast differs from brightness. State that by the end of the lesson they will be able to adjust contrast accurately, avoid common errors, and document their process.

1. Do‑now (5') – Quick quiz on brightness vs. contrast concepts.
2. Mini‑lecture (10') – Explain contrast, the mathematical formula, and the effect of the contrast factor c.
3. Teacher demonstration (10') – Adjust contrast on a sample image using both the slider and numeric entry, highlighting preview and clipping.
4. Guided practice (15') – Students work in pairs to adjust contrast on provided images, completing the worksheet checklist.
5. Peer review (5') – Pairs exchange images, discuss any loss of detail or colour shift, and suggest improvements.
6. Consolidation (5') – Whole‑class debrief of key observations and reminder of common pitfalls.

Summarise the steps for safe contrast adjustment and the importance of saving a new copy of the image. Students complete an exit ticket describing one tip to avoid clipping. For homework, each student selects a personal photograph, applies an appropriate contrast adjustment, and uploads both the original and edited versions to the class drive.