Bitmap file size calculation
I can explain how resolution and colour depth affect the file size of an image.
Bitmap file size calculation
I can explain how resolution and colour depth affect the file size of an image.
These resources will be removed by end of Summer Term 2025.
Lesson details
Key learning points
- The file size of a bitmap is determined from its colour depth and resolution.
- Increasing the colour depth of an image will increase its file size.
- Increasing the resoultion of an image will increase its file size.
- Selection of image resolution and colour depth depend on the use of the image and limitations imposed by the file size.
Keywords
Trade-off - accepting a limitation to achieve a beneficial outcome
Common misconception
Using a low resoultion or colour depth for an image makes it unusable.
A low resolution or colour depth does not necessarily make an image unusable. It depends on the purpose. Lower settings can be suitable for web use, icons or thumbnails, while higher quality is needed for printing or detailed graphics.
To help you plan your year 10 computer science lesson on: Bitmap file size calculation, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your year 10 computer science lesson on: Bitmap file size calculation, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
We use learning cycles to break down learning into key concepts or ideas linked to the learning outcome. Each learning cycle features explanations with checks for understanding and practice tasks with feedback. All of this is found in our slide decks, ready for you to download and edit. The practice tasks are also available as printable worksheets and some lessons have additional materials with extra material you might need for teaching the lesson.
The assessment exit quiz will test your pupils' understanding of the key learning points.
Our video is a tool for planning, showing how other teachers might teach the lesson, offering helpful tips, modelled explanations and inspiration for your own delivery in the classroom. Plus, you can set it as homework or revision for pupils and keep their learning on track by sharing an online pupil version of this lesson.
Explore more key stage 4 computer science lessons from the Representation of text, images and sound unit, dive into the full secondary computer science curriculum, or learn more about lesson planning.
Equipment
Licence
Lesson video
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Starter quiz
6 Questions
smallest element of an image
number of bits used per pixel
total number of pixels in an image
a group of 8 bits
Exit quiz
6 Questions
accepting a limitation to achieve a beneficial outcome
total number of pixels in an image
number of bits used per pixel
suitable for web use or thumbnails
suitable for printing or detailed graphics