Cloud Storage has both high-resolution and low-resolution backups.

High-resolution  and low-resolution Cloud Storage backup

High-resolution backup has two options:

• Optimized photos (recommended) - Default setting for RAW and JPEG images.
  This option will keep the original photo resolution while reducing the RAW file size by up to 4 times the original. 
  For example, if the image resolution is 24 megapixels and the original file size is 40MB, the backup image will remain 24 megapixels, but the file size will be reduced to as low as 10 MB.
  Imagen recommends this option because the upload time is faster, you can store up to 4 times more projects, and the original RAW photo resolution is preserved.
  
  
• Original photos - Creates a backup copy of your original photos (Raw and Jpeg).
  For example, if the image resolution is 24 megapixels and the file size is 40MB, the backup image will remain 24 megapixels and 10MB in size.
  JPEG photos will be uploaded as a copy of the Original photo even if "Optimized" is selected.

Low-resolution Cloud Storage backups have a reduced image resolution.

• Each project upload is backed up automatically in a low resolution of 1.5 megapixels.
• Low-resolution backup is free.

Photo quality comparison

High Resolution: Original vs. Optimized - High ISO image (100% zoom)
Size on disk: Original 45.9 MB vs. Optimized 23.1 MB

High Resolution: Original vs. Optimized - Low ISO image (100% zoom)
Size on disk: Original 28 MB vs. Optimized 7.4 MB

Low resolution vs. High resolution (Megapixel comparison, both images zoomed to 100%)