Check out the steps your files (image and non-image) go through as its uploaded to the server here
For images specifically, while the original image is being uploaded to your drive, the appearance within the Sagan will be downgraded for performance. After a file is being uploaded, we create different versions of your image with varying qualities to be used within your Sagan, giving you the most performant experience within Saganworks.
Take the example .jpg below, at full quality:
When we first add it to the Sagan and scale it up, it looks like this:
A few moments later, it looks like this:
If you double-click it to view it in close-up view, the image will be an even higher quality (closest to the original image)
Note: While we are adjusting the appearance of your files within a Sagan, when you or someone you share your Sagan with downloads the image, the original (highest quality) file will be downloaded.