You are able to adjust the overall image quality preset or individual compression settings for supported image types inside your image collection.
Advanced settings are also available for those users who want to configure each image format.
1. Click on the Content tab in the gray navigation bar.
2. Select the Collections option beneath the Content header.
3. Select the "Images" type to go to your image library.
4. Click on the Settings option in the top right corner of the library.
Within the Settings menu, you can choose how your images are displayed sitewide. Use the slider to pick between performance (on the left) and quality (on the right). If your site is hitting loading issues or if you have a large number of images within your pages and galleries of your site, try sliding over to the left to help the issue!
Choosing Advanced will give you even more options on how your site will deal with each type of supported image file type.