I'm glad somebody brought this up, so thanks for that.
300 DPI for raster images isn't an arbitrary number at all, like some other parent post mentioned. It's the standard target resolution for raster images being reproduced with standard AM screening at 150 lines per inch (LPI). We deal with it all the time in commercial printing.
In the early days of desktop publishing, some really smart guys figured out a simple formula for calculating proper resolution of scanned images for commercial reproduction with enough pixel density to hide stair stepping on AM screens: 2x the line frequency. 150 LPI was a very common standard for color lithography, so "scan your images at 300DPI/100%" became very common advice from prepress pros to page builders. My guess is that 300DPI turned into the magic number then. In reality, raster resolution should scale up or down with line frequency.
It could also be that 300DPI became an accepted norm because the original LaserWriter was a 300DPI device, and early desktop publishers thought that matching the output resolution of the LaserWriter was how to maximize quality. In reality, that device only produced about 51 LPI at 300DPI, so the quality return diminished above 100DPI for scanned images.
Based on my experience, 2x the AM line frequency actually cheats to the quality side a little. At 150 LPI, 225DPI images start to show pixelization a little, but over that makes you pretty safe.
For 1-bit images, matching the output device dot for dot will yield the highest quality. Commercial lithographic platesetters generally have an output resolution of 2400DPI to 3600DPI.
I've really struggled with that one. The form factor makes up a lot of the difference with a paper product. But I'm having trouble thinking of a real product application that would apply to the average joe (or me -- same thing?).
For instance, let's say this thing is called the Dell Sheet. Would I, my wife and each of my kids have their own Sheet? Would we sync our Sheets at regular intervals to fill it with offline content? Would my kids spread out their Sheet on the text to read some text in class? Is the Sheet so inexpensive that I have a couple of spares or is disposable?
I guess maybe yes is the answer to all those, but the idea doesn't resonate to me as the kind of thing that would take over the world. Perhaps it is.
Right on. I get that. That's sort of my point.
When I sit down on the plane, I really don't care to review an entire library of anything, and I'm probably not searching for anything in particular, or annotating or anything else. I just want to hold some glossy paper in front of my face to pass the time. Believe me, I understand the value of all those features. But it's the utility of a few sheets of paper that I turn to all the time.
So, I'm a long time prepress guy converted into a web designer and ultimately an online application developer. I make my living at a printing company that makes money putting ink on paper, and am always caught up in discussions and planning sessions where we prognosticate about what new electronic development is going to put a dent in the magazine business.
Lots -- and I mean lots -- of industry experts have been predicting that the Apple tablet would be the beginning of the end of print. Of course, this has been predicted many times before: CD-ROMs were going to do it, then the web, then web-based digital editions, and now the iPad. But this time, the talk was at a fever pitch. Bosacks alerts were coming out months before the mainstream media picked up on the initial iPad hype. Lots of people thought this would be the one.
And, it's not really, is it? And I didn't really think it would be either. When I try to imagine the electronic invention that replaces the utility of ink on paper (especially for magazines or other non-time-sensitive publishing), I can't really come up with an idea of what that might be. The online digital editions and iPad apps are cute -- even cool -- but they wouldn't stop me from throwing 128 pages of bound paper into a briefcase on a travel day. Besides, portable electronics are expensive and precarious. They need cases and screen protectors. They don't roll up. They aren't disposable if you spill your coffee on them.
So, what's it going to be? What will the technology look like that actually makes publishers stop printing on paper altogether? I really don't know.
C'est magnifique, mais ce n'est pas l'Informatique. -- Bosquet [on seeing the IBM 4341]