How many ink cartridges does the Canon PIXMA TR8620a use, and why does it have two different blacks?

The Canon PIXMA TR8620a runs five separate ink cartridges — including two different blacks: a pigment-based black for crisp text and a dye-based black for photo blacks, plus individual cyan, magenta, and yellow cartridges. Standard and XL high-yield variants are available; if you print with any regularity, the XL cartridges make more sense per page.