I exported a graph from Prism 3 Mac as a PICT file enlarged to 12X. Why does the graph look so bad when opened in PhotoShop?

Images saved at 12X and opened in PhotoShop look corrupted. This appears to be a bug in PhotoShop, because exported 12X Prism graphs look fine in other applications. The work-around is to export at 3X or 6X, not 12X.