Canon S820The S820 photo printer features the Canon Think Tank System™, an intelligent ink-management system that uses individual ink tanks for each color. You replace only the color that runs out rather than an entire cartridge.
This is the sight that greets you when you lift the cover on the S820 printer. Rather than seeing the usual color and black cartridges there's this most impressive looking print head assembly with six separate ink tanks.
Here's the print head with its six ink tanks (Black, Photo Cyan, Photo Magenta, Cyan, Magenta, Yellow). These are dye-based inks, not the pigment type. Not only can the user replace the individual ink tanks but you can also replace the entire print head if necessary. Epson printers require a trip to the service center if they encounter a print head problem. Unlike the newer Epson cartridges, the Canon ink tanks have no embedded computer chips and appear (but not tested by me) to be easy to refill.
Optical ink sensors automatically monitor all ink color levels and communicate with your computer--giving you a pop-up message indicating exactly what colors are running low. You can also check the status of the ink tanks at any time using the Status Monitor of the driver as shown above. Canon's optical low ink detection system prevents wasted printouts by notifying you via the Printer Status Monitor before any ink tank becomes empty, so you'll never unexpectedly run out of ink in the middle of a job again.
A light beam shines through a prism located at the bottom of each ink tank. When there is sufficient ink, the light is detected by the sensor. When only about 20% of ink is left in any of the ink tanks, the light beam is refracted, triggering the sensor which tells the printer driver to display a low ink tank notification for that ink tank.