Why do my sprites take more memory than they should?

My current project is using many sprites and I just realised the estimated memory usage in my largest layout is very high (4.2 GB) and my computer has a hard time opening the preview.

From what i gathered around other posts, sprites should take up about 4 bytes of memory per pixel. Thus a 1920 x 1080 pixel image should have a memory impact of around 8 mb. However images I use have a much higher impact...

For example, I created a test laytout with only 1920 x 1080 pixel background image in and the image memory records 23.8mb memory use! A fully empty scene still takes 2.3mb so that would mean the image takes 21.5mb of memory, almost 3 times as much as it should.

Has anyone encountered this or could point me in the right direction?

Thank you very much

If you right-click the project name in the Project Bar and select Tools - View spritesheets, you can see the images that Construct is really loading. Since everything is placed on spritesheets, it may be that a new image is added and it increases the spritesheet size by more than the image size. Usually Construct will pack a range of images on to spritesheets to reduce any waste, but you can also tweak the memory impact of it by adjusting the max spritesheet size in Project Properties.