[atlantaprog] Re: CD Booklet / Layout

Cool.  Thanks for the reply and the clarification. I definitely learned
a few things from this email!

Alex F/Brain21

> -----Original Message-----
> From: atlantaprog-bounce@xxxxxxxxxxxxx 
> [mailto:atlantaprog-bounce@xxxxxxxxxxxxx] On Behalf Of Allen 
> Welty-Green
> Sent: Sunday, January 19, 2003 10:21 PM
> To: atlantaprog@xxxxxxxxxxxxx
> Subject: [atlantaprog] Re: CD Booklet / Layout
> 
> 
> 
> >Do pdfs have resolution like raster art, or are they 
> independent like 
> >vector art?
> 
> PDF stands for "Portable document format". The are vector AND raster. 
> Fints and line-art graphics are handled as vectors, while photos and 
> other raster images are generally handled at whatever resolution they 
> were saved with.
> 
> >Whoa, wait a minute...  A tiff file is fixed at whatever you 
> saved it 
> >as.  Don't confuse people who have no clue what we are talking about 
> >and are trying to learn.  It's not like tiffs are ALWAYS 300 dpi and 
> >can never be anything else!
> >  We created this as a 600 dpi tiff file. There was no blurring of
> >edges present at all
> 
> True, tiffs are whatever resolution you save them as. The problem 
> comes in when you have very small text that is built out of several 
> process colors - or knocks out of several colors... in this case, 
> even 600 dpi is not sufficient resolution to guarantee that the edges 
> won't break up if the printing plates get slightly out of alignment 
> (a common occurrence). Imagesetters rasterize vector graphics (incl. 
> fonts) to whatever resolution they are set for, typically 2400 dpi 
> (dots per inch).
> 
> Another factor is line screen, typically 150 or 133. The is the 
> formula that's used to calculate the process color "dots" you see 
> when you look at printed photos up close. The line screen you use is 
> determined by the "dot gain" of your paper. This is how much the ink 
> will "spread" when it hits the paper. Coated magazine-type stock can 
> take 133-150 lines per inch, while newsprint and coarse cardboard can 
> only take about 70 or 80 before the start closing up and looking like 
> a mess! Your photo resolution should be twice your line screen. Any 
> additional resolution is ignored by the imagesetters. The colors you 
> use can make a big difference... text knocked out of solid black or 
> another solid color may look fine at even 300 dpi, while an orange or 
> purple or brown that's built out of high proportions of several 
> process colors can create big-time fuzzy edges if/when the plates 
> lose alignment.
> 
> Trapping is another factor. Trapping is the method that printers use 
> to insure clean edges if/when the plates get out of alignment. This 
> involves either spreading or "choking" two adjacent colors into each 
> other a bit so if something gets out of alignment, you don't see 
> white or jagged edges showing through. You can't trap a raster image 
> like a tiff. You can trap fonts and line art in a program like Quark 
> or Illustrator. When the imagesetter generates the film, it includes 
> the trapping info.
> 
> More reasons to have a pro - or at least a knowledgeable person to 
> guide you along. And you need to know all of this BEFORE you start 
> your design. For black text on white, like yours, Alex, it's probably 
> OK to just go with a tiff. 100% black ink has no line screen 
> issues... but if someone is working with elaborate design elements, 
> colors, etc.... there are just a boatload of variables!
> 
> Now everyone should take all of these discussions and compile them 
> and you'll have a pre-press 101 textbook!
> 
> AWG
>

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