The topic for this term’s ICT for year 6 is Digital Images and they will be working towards creating their own photo-story about e-safety using Comic Life. In our ICT lessons I am keen for the children to understand how the technology works rather than simply just using it and so the first couple of lessons in this unit have been about how computers display and store digital images.
In the first lesson we talked about how digital images are made up of pixels and that the smaller the pixels, the higher the resolution and therefore the better quality image. To demonstrate this I gave the children a sheet of 1cm x 1cm squared paper and asked them to create an image. They were told that each square had to be a solid colour and so they wouldn’t be able to include much detail. Once they had done that they were given paper with smaller squares and were asked to create a ‘high-resolution’ version of their image.
In the next lesson we looked at an image in PhotoShop and zoomed in so that we could see the individual pixels. We looked at how the computer uses numbers to represent each possible colour and that this is the data that the computer stores when you save an image. We saved the image as a .bmp file and looked at the file size which was over 27MB. I explained that this was because the file included the data for every single pixel. I then saved the image as a .jpg and asked the children if they could see any difference. They couldn’t and we then looked at the file size which was now down to 4MB. I asked the children if they had any ideas on how come the file size was so small. I used one of their images from the previous week and started reading out the pixels – “blue, blue, blue, blue, blue, green, green, blue…” and one of the boys said “why don’t you just say 5 blue, 2 green and so on?” which is basically how jpeg compression works. The children were then given some more squared paper and asked to create an image using 4 different colours inside a 10 x 10 square. They then had to record the data in their image by recording how many squares of a colour there were before it changed colour.
As a result we have some very interesting pictures to go on display and I hope the children now have a better understanding of how digital images are displayed and stored. I know it is not 100% technically accurate but I was more interested in the children understanding the concepts. Next week we will look at how digital cameras capture these images.