I recently worked with 4 large files of an atlas that I comped together to make one large world map. The comp size was about 15000 x 10000. I have 1.5 gigs of RAM and found that I could barely scrape by without getting out of RAM errors. If i added an effect to one of these layers it maxed out and i couldn’t render. But if it’s true that AE can only access 2 gigs of RAM then you’ll need to just carefully assess how much of each picture you’ll actually be seeing in the final output comp, and crop the images accordingly. In any case it will feel like swimming in wet cement with files that large. BTW, where’d you get that 100 megapixel camera?