4800 dpi - the resolution of your dreams. And, in your innocence, you believe the detail will be twice as fine as on a 2400 dpi printer. Well, it ain't. Like everyone else, when Canon says 4800 dpi, they don't mean actual resolution, but the number of "addressable" drops. Meaning that Canon printers still dispense the same number of drops as before - 2400 - but now they are distributed on the basis of an algorithm of 4800 available points per inch instead of 2400. For the moment, the new resolution has changed nothing: the drops of five picoliters are too big to make any difference when compared to a 2400 dpi print.
But the i550 has still upset the applecart: it costs less than the S750, uses the same cartridges and prints just as fast. So logically, it should gain the upper hand. Things change. But it might only be a temporary lead. Canon has the i850 up its sleeve, a 4800 dpi printer with two-picoliter drops.
We ran the same tests as usual: text, compound, monochrome and color documents, ordinary, draft and high definition resolution, etc. You can read a detailed description here .