Images are not being automatically resized, unless you specify that you want them to be. For example in a image library you have a tab called Default Image size. If you choose the images to be resized, they will be. However you will be able to browse their original size if you check the:
Don't resize, always upload original images
Please consider checking the attached screenshot.
the Telerik team
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items