malik@ut-emx.UUCP (Nadeem Malik) (10/24/88)
In article <7590@bloom-beacon.MIT.EDU> dyer@arktouros.MIT.EDU (Steve Dyer) writes: >In article <7099@ut-emx.UUCP> malik@emx.UUCP (Nadeem Malik) writes: >>In article <16961@shemp.CS.UCLA.EDU> lange@cs.ucla.edu (Trent Lange) writes: >>>An increase from 300 dpi to 400 dpi is a nearly 80 percent increase in actual >>>resolution, which I call more than slight. There are indeed 600 dpi printers >> >>Actually it is a 33% increase, but it is still quite significant. > >If I had a nickel for every comment like this from these "new mathematicians" >which I've got in the past few days, I'd have enough to buy my first NeXT >machine. Sorry, you don't get your nickel here:-) > >Get it folks: (400^2)/(300^2) is roughly 177/100, or a 77% increase. There is a ~77% increase in dot density, but NOT in the *quality or resolution* of the picture, which was under debate. If you would recall the original poster had questioned the increase in picture quality if we go from 300 dpi to 400 dpi. Resolution is the measure of the quality and it provides the distinguishability between close objects. It is given in pixels or dots or lines per unit of length and NOT as its *square* and that is why the resoultion of the printers is given as 300 *dots per inch*. In short the NeXT laserwriter would probably give a 33% increase in quality over the Apple Laser Writer. This is quite understandable intuitively as well. For example consider a printed letter like "C". Its printed quality depends upon the smoothness of its edges, which is clearly a function of the dots per inch and not the dot density. >Laser printers operate in two dimensions. Yes, I can agree with this. >--- >Steve Dyer >dyer@arktouros.MIT.EDU >dyer@spdcc.COM aka {harvard,husc6,ima,bbn,m2c,mipseast}!spdcc!dyer Nadeem Malik malik@emx.utexas.edu
jbn@glacier.STANFORD.EDU (John B. Nagle) (10/24/88)
Worth pointing out is that simply sending more dots per inch to the
engine will not necessarily increase the resolution. At some point, the
resolution of the xerographic process itself becomes the limiting factor.
It would be simple enough to crank a laser printing engine up to 600 DPI,
for example, just by cutting the spot size down, doubling the speed of
the rotating mirror, (or doubling the number of facets), and
quadrupling the data rate to the laser. But with today's engines, it
wouldn't really provide 600 DPI resolution; the xerographic process doesn't
have the resolution. Xerographic copiers, for example, still can't copy a
magazine page without a major loss of detail. There are limits to what can
be accomplished with a selenium photoconductor as the imaging medium, and,
in this, the fiftieth aniversary year of xerography, we seem to be very
near those limits.
This may be a good reason to finally move away from xerography and toward
other processes, such as ion-implantation printing, for which the physical
limits inherent in the process are higher. I doubt that we will ever have
the equivalent of glossy magazine pages coming out the slot of a xerography
based printer.
John Nagle