Notably in Chrome, if you right-click without zooming, you'll get the image at its smallest/medium resolution.
Workaround: If you want to DL the biggest one right now in Chrome, the trick is to open the "Inspect Elements" box, then go to the 'Resources' tab. The images you are looking for will be under Frames->[the page]->Images->...
Once you're in there, it'll be marked as max.gif (if I recall correctly). But there will be multiple of this file name, because it generates one in your cache each time you zoom an image. If the one you want isn't there, zoom in on a handout and it should pop up. You can right-click the file in the Resources listing and open it in a new tab.
It takes a bit, but once you get used to it, it's not a terrible workaround. It'd be hell for the average user to get used to, however. It works right now though.