What is DPI dependent on   The DPI measurement of a printer is dependent upon several factors including the method by which ink is applied the quality of the printer components and the quality of the ink and paper used  This is not true or at least is confusing  The DPI in the printing direction is dependent on the head firing frequency and the linear print speed The DPI in the advance direction perpendicular to the printing direction is dependent on the spacing of actuators eg nozzles for inkjet on a head and the angle of the heads Each of these can be multiplied by use of interleavingweaving using multiple passes andor multiple heads  What the original sentence may have been trying to get at is that different print modes can use different firing frequencies linear speeds interleaving factors etc and the effect of ink and media settings in print drivers is often to change the print mode possibly in addition to other software settings that dont affect DPI Also different print head technologies may improve at different rates in terms of firing frequency actuator spacing etc  On the subject of advertisements I strongly suspect that some of the dpi figures quoted in printer adverts are inflated You can inflate a dpi figure by   counting different colors as more than one dot this may be what  x  color dpi means  I expect it is really  x  in  colors   counting each dot printed by a variabledot head as more than one dot   saying equivalent dpi and making up a random number  This kind of creative arithmetic is all the result of trying to munge various resolution and quality factors into a single number for marketing purposes Its similar to how clock speed used to be used to indicate how fast a processor was At its worst it can lead to distorted technical decisions that maximize DPI with no improvement in or even at the expense of quality just as the Pentium  design was distorted to maximize clock speed  Its unlikely that someone could see a visible improvement in resolution above about  dpi with the unaided eye at a normal reading distance The extra quality that you can get from a higher dpi than that is not due to an increase in resolution its due to a reduction in graininess and possibly better hiding of head defects from using smaller drop volumes which requires you to use more dots in a given space to achieve the same ink density  To meaningfully compare printers you need at the very least to know the volume of ink in a drop for inkjet heads as of  this can vary from about  to  picolitres including what subdrop volumes are possible in the case of variabledot heads as well as the real dpi figure in each direction The overall quality will also depend on halftoning algorithms the gamut of the inks used color management positioning accuracy of the printer mechanism and any encoders head defects and how well the print mode hides them etc The intended application is also significant to give an extreme example theres no point in achieving photographic resolution in a printer that will be used to print billboards  although color gamut would still be very important for the latter    employed by but not speaking for a printer manufacturer