I tried uploading an album to Google+ via Picasa.  I tried selecting both Original Size Images as well as 2048 Max width options. (Photos are 8MP and I have not run out of free storage.)But the photos are uploaded in 800x600.  What could be the reason behind this?  Picasa shows two blue rounded arrows next to each photo.  Does it mean that it has only uploaded thumbnails/previews and not the entire photos?
Google+ Picasa photo upload - low resolution
google plus photos