venkat@brand.usc.edu (V. Venkat) (10/19/88)
> >This is just a wild guess, but I would tend to bet that the text processing >and desktop publishing is VERY WYSIWYG! The display is Display Postscript >and the laser printer is Postscript. It makes sense that things on the >screen are going to come out pretty much the same on paper. > >The laser printer is 400 dpi (WOW). What I want to know is the screen >resolution (in dpi). > >Bryce Jasmer >jasmerb@jacobs.cs.orst.edu With a 17" diameter screen i.e. apprx 12" X 12" screen and a 1024X1024 pixels -- the screen resolution will be about 86 pixels per inch. Since the printing is essentially WYSIWYG a laser printer with 86 dpi will suffice. What is the use of a 400 dpi laser printer unless the screen represents only a part of the printed page and you have some scrolling mechanism? Maybe I haven't understood the fundamentals here. Can someone illuminate me further on this matter. Much thanks. V. Venkat.
chiaravi@silver.bacs.indiana.edu (Lucius Chiaraviglio) (10/19/88)
In article <12908@oberon.USC.EDU> venkat@brand.usc.edu (V. Venkat) writes: >With a 17" diameter screen i.e. apprx 12" X 12" screen and a 1024X1024 pixels >-- the screen resolution will be about 86 pixels per inch. >Since the printing is essentially WYSIWYG a laser printer with 86 dpi >will suffice. What is the use of a 400 dpi laser printer unless the screen >represents only a part of the printed page and you have some scrolling >mechanism? Maybe I haven't understood the fundamentals here. Can someone >illuminate me further on this matter. Much thanks. I can't claim to know much about the NeXT machine in particular, but what is going on here, as what goes on with printing from a Macintosh (especially to a laser printer but also to ImageWriters) is not quite WYSIWYG (in which case your complaint would be entirely valid) but WYSIAWYG (I don't know if this is an official abbreviation -- actually I doubt it -- but it stands for What You See is Almost What You Get). What this means is that the software has an idea of what things are supposed to look like which (hopefully) matches your idea, and the best mapping of this into the available resolution is done for each display device, be it screen or printer. Thus, you see an 86 dpi (72 dpi on a Macintosh) representation of your document on your screen, and a 400 dpi (300 dpi on any of the LaserWriters, 216 dpi on an ImageWriter LQ in Best mode, 144 dpi on an ImageWriter II (I'm not sure about I) in Best mode, and 72 dpi on any ImageWriter in Faster mode). On the more advanced model of LinoTron you would get something like a 2540 dpi representation of your document (don't quote me on that last number). The screen may or may not represent all of the printed page, depending on the physical dimensions of the screen and the degree of magnification/ demagnification in the screen representation of your document. I'm not sure about the NeXT hardware/software combination, but Macintosh software is supposed to give you neither magnification nor demagnification on a 72 dpi screen (like the standard Macintosh screens) unless you specifically ask for it (like Page Preview... in Microsoft Word and Zoom In/Zoom Out in MacDraft and sundry similar options in other Macintosh programs). Hope this helps. -- Lucius Chiaraviglio ARPAnet: chiaravi@silver.bacs.indiana.edu BITNET: chiaravi@IUBACS.BITNET (hoses From: fields; INCLUDE RETURN ADDRESS) USENET: iuvax!silver!chiaravi -- -- Lucius Chiaraviglio ARPAnet: chiaravi@silver.bacs.indiana.edu BITNET: chiaravi@IUBACS.BITNET (hoses From: fields; INCLUDE RETURN ADDRESS) USENET: iuvax!silver!chiaravi
shap@polya.Stanford.EDU (Jonathan S. Shapiro) (10/19/88)
In article <12908@oberon.USC.EDU> venkat@brand.usc.edu (V. Venkat) writes: >Since the printing is essentially WYSIWYG a laser printer with 86 dpi >will suffice. What is the use of a 400 dpi laser printer unless the screen >represents only a part of the printed page and you have some scrolling >mechanism? Indeed you haven't understood the fundamentals. Several factors apply. First, the luminance of paper is considerably different from the luminence of a CRT - an acceptable dot density on one would not be acceptable (necessarily) on the other. More important, the fact that your screen fonts look (relatively) cruddy is no reason why everything you print should look amateurish. 86 DPI is a reasonable compromise between speed of drawing for interactivity and readability over a long stretch. It is not a good compromise for printed text. Since the problems are different, the DPI is different. Jon
cjc@ulysses.homer.nj.att.com (Chris Calabrese[rs]) (10/20/88)
In article <2467@silver.bacs.indiana.edu>, chiaravi@silver.bacs.indiana.edu (Lucius Chiaraviglio) writes: < In article <12908@oberon.USC.EDU> venkat@brand.usc.edu (V. Venkat) writes: < >With a 17" diameter screen i.e. apprx 12" X 12" screen and a 1024X1024 pixels < >-- the screen resolution will be about 86 pixels per inch. < > [...] > > I can't claim to know much about the NeXT machine in particular, but > what is going on here, as what goes on with printing from a Macintosh > (especially to a laser printer but also to ImageWriters) is not quite WYSIWYG The important part of this issue is PostScript! The PostScript language has no concept of pixels/resolution/etc.; therefore, programs output what they think is WISIWYG, and it's up to the PostScript display software to map it to the best resolution of the devece. What You See IS What You Get - PostScript code. -- -------- Christopher J. Calabrese AT&T Bell Laboratories ulysses!cjc
cloos@batcomputer.tn.cornell.edu (James H. Cloos Jr.) (10/20/88)
In article <12908@oberon.USC.EDU> venkat@brand.usc.edu (V. Venkat) writes: |>This is just a wild guess, but I would tend to bet that the text processing |>and desktop publishing is VERY WYSIWYG! The display is Display Postscript |>and the laser printer is Postscript. It makes sense that things on the |>screen are going to come out pretty much the same on paper. |> |>The laser printer is 400 dpi (WOW). What I want to know is the screen |>resolution (in dpi). | |With a 17" diameter screen i.e. apprx 12" X 12" screen and a 1024X1024 pixels |-- the screen resolution will be about 86 pixels per inch. |Since the printing is essentially WYSIWYG a laser printer with 86 dpi |will suffice. What is the use of a 400 dpi laser printer unless the screen |represents only a part of the printed page and you have some scrolling |mechanism? Maybe I haven't understood the fundamentals here. Can someone |illuminate me further on this matter. Much thanks. The article from BIX mentioned ~94 pix / inch. My guess is that they wanted 100, and the 94 was as close as was economically feasible. The printer is 400 dpi because you want high resolution on the printed page, so that it looks more like professionally prited stuff than like computer output. It does have a 300 dpi draft mode when speed or memory is more important than resolution. (If the imaging area were 8.5x11, which is isn't, the trade off is 14.96 million bits vs. 8.415 million bits, a considerable amount. If the difference means paging, the slowdown could be considerable.) (BTW, as to why I think they wanted 100 dpi on the monitor: converting 100 to 300 or 400 is considerable easier than converting 94.3 to 300 or 400. Maybe they even run the monitor as if it were 100 dpi rather than the 94+-.) -JimC -- batcomputer!cloos@cornell.UUCP |James H. Cloos, Jr.|#include <disclaimer.h> cloos@batcomputer.tn.cornell.EDU|B7 Upson, Cornell U|#include <cute_stuff.h> cloos@tcgould.tn.cornell.EDU |Ithaca, NY 14853 |"Entropy isn't what cloos@crnlthry.BITNET | +1 607 272 4519 | it used to be." a.k.a. jhc@vax5.ccs.cornell.EDU or jhc@crnlvax5.BITNET
chiaravi@silver.bacs.indiana.edu (Lucius Chiaraviglio) (10/20/88)
In article <12908@oberon.USC.EDU> venkat@brand.usc.edu (V. Venkat) writes: [About the NeXT screen and laser printer resolution] >With a 17" diameter screen i.e. apprx 12" X 12" screen and a 1024X1024 pixels >-- the screen resolution will be about 86 pixels per inch. >Since the printing is essentially WYSIWYG a laser printer with 86 dpi >will suffice. What is the use of a 400 dpi laser printer unless the screen >represents only a part of the printed page and you have some scrolling >mechanism? Maybe I haven't understood the fundamentals here. Can someone >illuminate me further on this matter. Much thanks. Many word processing and graphics programs -- especially the ones on the NeXT and the Macintosh -- are called WYSIWYG: What You See is What You Get. However, that is not quite an accurate description of the real key concept, which is WYSIAWYG: What You See is Almost What You Get. With Macintosh programs -- and I assume the idea is similar (although different in implementation) with the NeXT programs -- you have your document on the computer, whose concept of what it looks like hopefully is equivalent to your concept of what it looks like. On whatever display device you are using -- screen, laser printer, or ImageWriter (Macintosh only) -- you see your document mapped to whatever resolution the display device is capable of (on ImageWriters, this depends on which print quality you have selected). Thus, on the NeXT screen you get an 86 dpi representation of your document; on the NeXT laser printer you get a 300 dpi or 400 dpi representation of your document; on a Macintosh screen or an ImageWriter in Faster mode you get a 72 dpi representation of your document; on a LaserWriter you get a 300 dpi representation of your document; and on the latest model of LinoTron you get a 2540 dpi representation of your document (don't quote me on that last number). Depending on the physical size of your screen and how much magnification/ demagnification is applied to documents displayed on it under your chosen hardware/software combination, the screen may or may not be able to show all of a printed page at once, but your document is generally not shown with the same resolution on the screen as it will have when printed unless you have selected magnification (-: massive magnification if you are editing a bitmap to be typeset on a Linotron :-) or unless you are on a Macintosh and printing your stuff on an ImageWriter in Faster mode. Hope this helps. -- Lucius Chiaraviglio ARPAnet: chiaravi@silver.bacs.indiana.edu BITNET: chiaravi@IUBACS.BITNET (hoses From: fields; INCLUDE RETURN ADDRESS) USENET: iuvax!silver!chiaravi -- -- Lucius Chiaraviglio ARPAnet: chiaravi@silver.bacs.indiana.edu BITNET: chiaravi@IUBACS.BITNET (hoses From: fields; INCLUDE RETURN ADDRESS) USENET: iuvax!silver!chiaravi
steve@violet.berkeley.edu (Steve Goldfield) (10/20/88)
In article <2482@silver.bacs.indiana.edu> chiaravi@silver.UUCP (Lucius Chiaraviglio) writes:
About resolution in displaying screen vs. print images.
I appreciated the information you posted. However, as I posted
to comp.sys.mac yesterday, not all the discrepancies between
screen and printer can be ascribed to resolution. I gave two
examples in PageMaker. In one case, I drew a jagged line
across the screen and tried to put bullets on the nodes.
[Please don't tell me that I could have bought software like
MacFlow to do this. That isn't the point.] One of the bullets
printed about half an inch away from the node it was supposed
to be coincident with and which it was coincident with on the
screen. I phoned Aldus at the time, and they admitted that
such things could happen. [I admit that I don't know if this
is just a bug or laziness on their part or an inherent problem
as Aldus claimed.] In a second example, which has happened to
me twice, my screen showed a box, but the laser printer failed
to print one of its corners. In that case, I copied everything
into MacDraw which printed the box in its entirety.
[Incidentally, I always use the Aldus driver with PageMaker
because the Apple driver doesn't seem to handle reversed fonts.]
If the problem is only the inferiority of PageMaker, it isn't
worth discussing here except to warn people away from it. But
if something more fundamental in the interaction between
applications and the Mac screen and laser printer is going on,
then I for one would be interested in knowing what it is and
what real limitations it imposes on application programmers.
And for this news group, I'd be interested in knowing if the
problem is eliminated on the NeXT.
It seems quid pro quo to raise this here since the NeXT got so
much discussion in comp.sys.mac.
Steve Goldfielddzenc@hermes.ai.mit.edu (Daniel Zenchelsky) (10/21/88)
In article <12908@oberon.USC.EDU> venkat@brand.usc.edu (V. Venkat) writes: >With a 17" diameter screen i.e. apprx 12" X 12" screen and a 1024X1024 pixels >-- the screen resolution will be about 86 pixels per inch. >Since the printing is essentially WYSIWYG a laser printer with 86 dpi >will suffice. What is the use of a 400 dpi laser printer unless the screen >represents only a part of the printed page and you have some scrolling >mechanism? Maybe I haven't understood the fundamentals here. Can someone >illuminate me further on this matter. Much thanks. > >V. Venkat. Thats the beauty of PostScript. It is NOT Bit-Mapped, it is an object oriented language. Instead of defining each of the dots on a circle, you tell the printer (or postscript display) to draw a circle of radius x. It then prints the circle at the highest resolution it can. on an 86 pixel per inch screen the circle will come out nice looking, on a 300 DPI printer, it will look VERY smooth, and on a 400 DPI printer, I doubt you'd be able to tell it came from a printer! -Dan +-----------------------------------------------------------+ | ______ | | || |o| Daniel Zenchelsky -- dzenc@hermes.ai.mit.edu | | ||___| | | | | _ | "If it's not in the computer, it doesn't exist" | | \_[]_|_| | | | +-----------------------------------------------------------+
bob@allosaur.cis.ohio-state.edu (Bob Sutterfield) (10/21/88)
In article <6637@batcomputer.tn.cornell.edu> cloos@tcgould.tn.cornell.edu (James H. Cloos Jr.) writes: >(BTW, as to why I think they wanted 100 dpi on the monitor: converting 100 >to 300 or 400 is considerable easier than converting 94.3 to 300 or 400. >Maybe they even run the monitor as if it were 100 dpi rather than the 94+-.) The content of a PostScript-driven display is not represented internally as a bitmap in screen resulution. The image is maintained in PostScript, then interpreted when the image needs to go to the rendering medium. The interpreter knows the resolution and other properties (e.g. color, grayscale, spot shape, spot size, inter-spot spacing) of the medium and applies antialiasing and other techniques appropriately at display time. In the case of the NeXT machine, the interpreter knows that the screen has certain properties and the printer has certain other properties. One internal representation is sufficient to generate the image on either rendering engine. Neither engine's rendering properties matter, nor does the ratio between the two. -=- Zippy sez, --Bob How's it going in those MODULAR LOVE UNITS??
spolsky-joel@CS.YALE.EDU (Joel Spolsky) (10/22/88)
In article <25354@tut.cis.ohio-state.edu> bob@allosaur.cis.ohio-state.edu (Bob Sutterfield) writes: | In article <6637@batcomputer.tn.cornell.edu> cloos@tcgould.tn.cornell.edu (James H. Cloos Jr.) writes: | | (BTW, as to why I think they wanted 100 dpi on the monitor: converting 100 | | to 300 or 400 is considerable easier than converting 94.3 to 300 or 400. | | Neither engine's rendering properties | matter, nor does the ratio between the two. Well, not entirely true. A font that looks good in 100dpi will look much the same in 400dpi, however, a font that looks good in 94.3 might look a bit weird in 400 due to rounding errors. This is more of a problem scaling down to courser resolutions. For example, if in 400 resolution we have: 111100001111 (note that each line is exactly the same width) Then in 100 resolution we have 101 (equality is preserved). BUT, in 150dpi resolution (for example), we happen to need exactly 1.5 dots in each field, and the rounding might be resolved unequally: 1011 Yes, I know that these rounding errors will occur whenever you rasterize postscript, however, at least you can be sure that if something looks good on the screen, it will look much the same printed. So, if you have two hairlines that are 1 pixel each on the screen, you can be sure that one will not be printed as 3 pixels and the other as 4 pixels. (If you think this is a moot point, look at how bad unevenly scaled fonts look in Microsoft Windows or the MacIntosh. In the former the same letter is often represented two different ways on the screen). another random thought from +----------------+---------------------------------------------------+ | Joel Spolsky | bitnet: spolsky@yalecs uucp: ...!yale!spolsky | | | arpa: spolsky@yale.edu voicenet: 203-436-1483 | +----------------+---------------------------------------------------+ #include <disclaimer.h>
cramer@optilink.UUCP (Clayton Cramer) (10/23/88)
In article <25354@tut.cis.ohio-state.edu>, bob@allosaur.cis.ohio-state.edu (Bob Sutterfield) writes: > In article <6637@batcomputer.tn.cornell.edu> cloos@tcgould.tn.cornell.edu (James H. Cloos Jr.) writes: > The content of a PostScript-driven display is not represented > internally as a bitmap in screen resulution. The image is maintained > in PostScript, then interpreted when the image needs to go to the > rendering medium. The interpreter knows the resolution and other > properties (e.g. color, grayscale, spot shape, spot size, inter-spot > spacing) of the medium and applies antialiasing and other techniques > appropriately at display time. > > In the case of the NeXT machine, the interpreter knows that the screen > has certain properties and the printer has certain other properties. > One internal representation is sufficient to generate the image on > either rendering engine. Neither engine's rendering properties > matter, nor does the ratio between the two. So how much hassle is it going to be for someone with a NeXT machine to connect up a 1270 dpi PostScript typesetter and make it work? Will the NeXT machine have enough smarts to output true PostScript without knowledge of the rendering engine? (I sure hope so -- or my opinion of NeXT will tkae a nose dive). -- Clayton E. Cramer ..!ames!pyramid!kontron!optilin!cramer
bob@allosaur.cis.ohio-state.edu (Bob Sutterfield) (10/25/88)
In article <588@optilink.UUCP> cramer@optilink.UUCP (Clayton Cramer) writes: >So how much hassle is it going to be for someone with a NeXT machine >to connect up a 1270 dpi PostScript typesetter and make it work? If our experiences with various PostScript printers are any guide, you'll have more trouble getting the serial line flow control to work right. Once that calms down, you can use the standard Berkeley remote line printer daemon stuff to drive any PostScript printer, just like when you run TranScript on a networkful of other machines with only one PS printer around. >Will the NeXT machine have enough smarts to output true PostScript >without knowledge of the rendering engine? (I sure hope so -- or my >opinion of NeXT will tkae a nose dive). Surely you can find plenty of better reasons to lower your opinion of NeXT! Jobs' nose is too big, etc... :-) To print to a PostScript device that's not attached on the custom interface, you'll just ship the PostScript off across the net. Then the engine in the printer (e.g. Apple LaserWriter, DataProducts 2665, whatever) will worry about its own device's rendering attributes. At that point, it's not NeXT's problem. -=- Zippy sez, --Bob Can I have an IMPULSE ITEM instead?
casseres@Apple.COM (David Casseres) (10/26/88)
In article <12908@oberon.USC.EDU> venkat@brand.usc.edu (V. Venkat) writes: >With a 17" diameter screen i.e. apprx 12" X 12" screen and a 1024X1024 pixels >-- the screen resolution will be about 86 pixels per inch. >Since the printing is essentially WYSIWYG a laser printer with 86 dpi >will suffice. What is the use of a 400 dpi laser printer unless the screen >represents only a part of the printed page and you have some scrolling >mechanism? Maybe I haven't understood the fundamentals here. Can someone >illuminate me further on this matter. Much thanks. Aha, we are into the wonderful wierd world of "just what DOES WYSIWYG really mean, anyway?" First, when Alan Kay coined the phrase it was not about visual fidelity between a computer screen and printed paper at all; it was about having a good visual representation (on screen) of your work, i.e. the contents of your head. At least that's how I understand it. But of course Kay's meaning has now disappeared in a fog of marketing hype. In its purest form the hype goes "what you see on the screen is EXACTLY what will be printed." Of course this is baloney. If it were true it would mean you just get a printed screen dump, at screen resolution, but nobody has ever been satisfied with that. A slightly more evolved form of the hype is "what gets printed is exactly what you saw on screen, only you couldn't see ALL of it on screen without scrolling, and the printed image is nicer because the printer has higher resolution." A very simple but bogus statement is struggling to turn into a rather complicated, somewhat less bogus statement. Myself, I like to avoid the term WYSIWYG when talking about printing, and use the term "visual fidelity." To me this means that the imaging and printing software will go through whatever contortions are necessary to render an ideal page image on the screen and on the printer, finding the best balance of A) quality of the printed image, B) quality of the screen image, and C) geometric and graphical correspondence between the two images. This is an extremely complicated and difficult problem to solve, EVEN when you get to use PostScript for both the screen and the printer. For example, users want to have 8-point text. Hell, they even want 6- point, and the printer prints 6- point beautifully. If you use the same letter designs on the screen (graphical fidelity), the tiny letters are illegible. If you change the letter designs for small sizes so as to make them legible, they don't lay out the same way any more, i.e., you find you have not only given up graphical fidelity but geometric fidelity as well. The string of letters may overlap something on paper that it didn't overlap on the screen, or a margin that was straight on the screen is ragged on paper, etc. For another example, PostScript is "resolution independent" and everything you draw can be arbitrarily scaled. That's a nice way to take care of differing resolutions on the screen and printer. But people want to in- corporate scanned images into their documents, and scanned images are bitmaps, and bitmaps are NOT resolution independent. When you scale them, ugly artifacts appear. Because of problems like these, achieving visual fidelity is as much an art as a science; a lot of judgement has to be used, and ultimately the solutions that emerge are the result of history and the interactions of system designers, application designers, and end users. The solutions on the Mac have always had a strong tendency to become printer-dependent, as third party developers sought to squeeze every bit of advantage out of each kind of printer; this has added to the general complexity of the problem. I'll be watching NeXT's development from a relatively clean slate with great fascination. David Casseres
casseres@Apple.COM (David Casseres) (10/26/88)
In article <15757@agate.BERKELEY.EDU> steve@violet.berkeley.edu (Steve Goldfield) writes: >... in PageMaker. In one case, I drew a jagged line >across the screen and tried to put bullets on the nodes. >... One of the bullets >printed about half an inch away from the node it was supposed >to be coincident with and which it was coincident with on the >screen. I phoned Aldus at the time, and they admitted that >such things could happen. [I admit that I don't know if this >is just a bug or laziness on their part or an inherent problem >as Aldus claimed.] HALF AN INCH? If it's an "inherent" problem, it's inherent in Page- Maker, not in any part of the Mac system. > In a second example, which has happened to >me twice, my screen showed a box, but the laser printer failed >to print one of its corners. In that case, I copied everything >into MacDraw which printed the box in its entirety. Which demonstrates that this one, too, is a PageMaker problem. >If the problem is only the inferiority of PageMaker, it isn't >worth discussing here except to warn people away from it. But >if something more fundamental in the interaction between >applications and the Mac screen and laser printer is going on, >then I for one would be interested in knowing what it is and >what real limitations it imposes on application programmers. >And for this news group, I'd be interested in knowing if the >problem is eliminated on the NeXT. I assure you there is nothing more fundamental than an application bug here. There ARE fundamental problems with WYSIWYG, but they show up in much more subtle ways -- not half-inch errors and missing parts of objects. David Casseres