YEAR 10 · IN PAIRS · 24 MINUTES
Small file. Still useful?
You’re choosing images for a school website. Find the smallest file that still does its job.
Answers stay on this device. Nothing is submitted automatically.
Choose your assigned image
One person compares; the other records. Swap roles halfway.
Make a prediction
Study the original before looking at the compressed versions.
Need a reminder?
Palette reduction limits the colours an image can use. JPEG discards some image detail. Either can change how an image looks. Its purpose decides whether that change is acceptable.
How far can you push it?
Drag left until the image stops doing its job. Then pull it back to a setting you would accept.
Fewer colours can remove colour differences. The pixel dimensions stay the same.
Quick comparison settings
Click either image to choose a detail. The same area is enlarged below. Judge overall suitability at normal viewing size too.
Record this setting
Record at least two palette sizes and two JPEG settings. Include a setting that goes too far.
Your notes stay with this setting when you move the slider.
Your evidence
| Version | File size | Visible changes | Acceptable? |
|---|
What do these file sizes mean?
These are the actual sizes of the downloadable files, including headers. The reference is a lossless PNG, so it is already compressed. The palette slider selects indexed PNG files with 2 to 256 colours; the JPEG slider selects quality settings from 1 to 100. Every version was made directly from the same reference at the same dimensions. A different format can sometimes make a file larger.
Make your recommendation
Choose the smallest version you consider acceptable. You may keep the original.
Stretch: calculate the change in file size
Percentage reduction = (reference size − chosen size) ÷ reference size × 100. A negative answer means the chosen file is larger. Why might a different use of the image change your decision?
Compare with another pair
Find a pair with a different image. Each pair has one minute to explain its choice, then discuss the difference.
Explain
Which version did you choose, and what evidence supports it?
Challenge
What would be lost if you chose an even smaller file?
Connect
Why might your two images need different approaches?
Is the smallest file always best?
Answer individually. Use a specific example from today’s activity.
Keep your evidence
Download your answers before leaving this device. Follow your teacher’s instructions for handing them in.