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Colophon

The base font for this page is Trebuchet MS, a free font from Microsoft designed for on-screen readability at small point sizes. The headlines are 32 pt Times bold italic, combining elegance, classical proportions, and compactness.

The logo is variation on the original logo from Aldus PageMaker and depicts Aldus Manutius, a student of Johannes Gutenberg and inventor of italics. This is to echo the roots of desktop publishing, both in the 1450s and the 1980s. The logo uses Courier from ITC to evoke the feel of metal type and Poetica from Adobe Systems to evoke the era of hand lettering.

Made on a Macintosh using Adobe Photoshop and Macromedia DreamWeaver.

An Introduction to Scanning for the Beginning Desktop Publisher

by Peter C.S. Adams <adamsp@cs.umb.edu>, Dan Johnston <dan@COPIES-ETC.COM>, and Rick Strong, Ottawa, Canada.

Now that scanners can be bought for less that US $100 and good quality laser printers for less than US $500, more and more people are becoming their own publishers. Often, these people are disappointed with the results.

Recommended File Formats

> I have been told that you should only place pictures in PM as .tif. Is
> that true? (Is .jpg bad for printing?) When I download the camera's
> photos to my PC it will be in some proprietary format, right? What do I do
> then? Do I save it as a .tif then? If I save it as a .jpg, and later
> convert it to .tif, will it lose data?

TIFF is the best format for photos. JPEG is "lossy," meaning part of its compression involves deleting information. But the algorithm is extremely clever and most people will never notice the missing data. So the answer to your questions (most of them, anyway) is NO. TIFF is best, but not the ONLY format you can use. JPEG is perfectly fine in many instances -- it was invented by the Joint Photographic Expert Group for the purpose of saving photographs, after all. Just make sure you have not over-compressed it or repeatedly compressed it -- open a JPEG, alter it, and save it in JPEG format, and you lose MORE data. If you will be touching up the photo (in Photoshop, e.g.), work in TIFF, then (optionally) save the final result in JPEG and you should be OK. Converting a JPEG to TIFF will not lose any data, but converting a TIFF to JPEG will.

What Resolution to Choose

If you were SCANNING a photo, you would want to calculate the size and resolution, using the rule of thumb "Scan DPI should be 1.5-2x the output LPI." But you may not have a choice if you are using a digital camera. Many cameras save photos in JPEG format by default, to save memory in the camera, and very few give you any control over resolution. One thing you may have to do is reduce the size of your photo in order to gain resolution (resolution is dots per inch, so reducing the size in inches increases the DPI). Note: I'm using some of these terms a little loosely, which might get me flamed on the Photoshop list! If you're unfamiliar with any of these terms, you can ask here or look them up in the DTP Glossary.

> I have a customer who gave me digital pictures for their newsletter in
> the form of 72 dpi jpegs.

72 dpi isn't much -- only enough for about a 50 line halftone screen, about what you'd get from an old 300 dpi laser printer. Happily, this doesn't mean much. Remember, your digital image's size is measures in pixels, and your resolution is measures in pixels per inch.

It's like saying "It's 100 miles to the nearest gas station and my car gets 30 miles per gallon. Can I make it?" There isn't enough information. You need to know how many gallons of gas you have left.

That picture could be 15" wide at 72 dpi or 1" wide at 72 dpi. Just make sure that when placed at the correct size the picture's resolution is greater than 72. You may want to open the pictures in Photoshop, tweak them if needed, set the resolution you want, and save them as TIFFs.

Anyway, the ratio between pixels per inch to lines per inch is mildly controversial. Some say 1.5 to 1, someone posted recently about a book (?) that advocated 1.4 to 1 (square root of 2 is 1.414...), and some say 2 to 1.

Output
DPI Typical
Halftone High Res
Color/Grey Typical
Color/Grey Black &
White

300    53 lpi   106 dpi     80 ppi 300 ppi

   600 75 lpi   150 dpi    115 dpi   600 ppi

  1200   133 lpi   266 dpi    200 dpi 1200 ppi

  2400   266 lpi   532 dpi    400 dpi 2400 ppi

  3000   300 lpi   600 dpi    450 dpi 3000 ppi

Since the only cost of having too many pixels is time and disk space, I would tend to agree with Rick's numbers for color/greyscale. But B&W? B&W images are not screened, so you just use as much data as the scanner can grab and the output device can print. E.g. I always scan text, line drawings, etc., at 600 dpi. The chart to the right will give you reasonable values for scanning various types of images for various applications.

By the way, if you started out in photography, you may still think in terms of colour photos and B & W photos, especially when someone refers to "pictures." Greyscale is a recent invention of the computer age, while "a Greyscale" has been part of the Graphic arts industry for some time. Continuous tone (contone) may be a more accurate term for colour or B & W images (photos and art) which require screening. Line drawings and other types of artwork are another matter. Sure, use 600, 800 or 1200 optical dpi whenever you can. Optical dpi is the raw dpi produced by the mechanism and optical elements of the machine, not generated by mathematical magic.

Black and White or Color?

When most people say black and white, they really mean greyscale. This means capturing all the tonal quality in a black and white photo. Real black and white refers to capturing only the black information and the white information, losing any gradations in between. This is also called "one bit," meaning all the information for a given spot can be represented as either on (black) or off (white). Greyscale uses 8 bits to capture 256 shades of grey. Color can range anywhere from 8 bits to 36 bits.

The Difference Between Laser Printer Output and Imagesetter Output

Laser printers typically output 600 dpi. Imagesetters range from 2400 dpi up. This means that the line screens (halftone screen) on an imagesetter

But that's not all. Imagesetters output to film, not paper, and use light, not toner, to make the image. This means there is no paper stretching or misplaced toner, making the images more uniform and exact. In addition, some laser printers use "resolution enhancement" (RET) to make their halftones more

Options Available in PageMaker

Once the photo is in PageMaker, crop to your heart's content. This will not affect the original in any way, only what is sent to the printer. Note, however, that all the data in a cropped photo will still be sent, making transmission and RIPping slower. It is usually better to place a photo in PageMaker after it has been edited, not before.

If you are sending this to a service bureau or your printer, ASK THEM WHAT TO DO. Some will have strong feelings one way or the other, and some will require RGB, although most will want CYMK. There's no way to know without asking, and as a side benefit, you'll learn something, save money, and get a better looking brochure.

> we have a very striped and ugly greyscale tiff box.
> We think the problem lies in the number of pixels per inch we chose.
> Photoshop suggested 71 pixels, but that sounded very little so we tried 180
> pixels. It looked great in Photoshop, but it is simply awful in Pagemaker.

The difference between Pixels, Dots, and Lines Per Inch

Pixels per inch, dots per inch, and lines per inch are confusingly similar sounding. Monitors display dots per inch. Scanners scan in pixels per inch, which is also the unit of Photoshop. Digital cameras simply capture pixels (e.g. 1024x768).
An 8x8 halftone cell with half of the cells on (black) yields 50% grey.

Printing an image is a different matter altogether. Laser printers, unlike monitors, cannot display greys, only black or white. So to simulate grey, they break up your image into "halftone cells." An 8x8 cell has 64 pixels in it, so it can display 64 greys. This is called the "line screen" or "halftone screen." This reduces the amount of detail in the photo accordingly. A 600 dpi printer produces 64 greys (if memory serves) by 600/8 or 75 lines per inch. The more greys, the less resolution, and the larger and more visible the halftone dots. So a 600 dpi printer trying to reproduce 256 shades of grey could only manage 38 lines per inch! This is why people are willing to pay service bureaus for 2400 dpi imagesetter output.

Your display problem is likely the fact that PageMaker is using a low resolution version of your image. In Preferences, change "Graphics Display" to high resolution and see if that helps. But output may still be a problem: see below.

> Geoff Heard mentioned that Photoshop does a lot of dithering and stuff to
> make gradients look better. Is there some magic number of pixels per inch
> which will look good in Pagemaker - and keep looking good when we send the
> finished job to the service bureau ?

Like any continuous tone material (color photos, greyscale photos, gradients, etc.) you want your image to be 1.5x to 2x the number of pixels per inch as your final output will be in lines per inch.

Monochrome images (line drawings, text, etc.) should simply be scanned at the highest possible number of pixels per inch to preserve detail.

> Oh, sorry, We should have explained that it looks even more stripy and
> awful when we print it with 600 dpi on our laserprinter.

Depending on the settings you have applied, your LaserWriter may be trying to print a higher number of lines per inch and therefore printing fewer greys. This means you have places where there is a large jump in the shade of grey. Instead of a nice transition as you see on the screen in Photoshop, you instead see a jump from, say, 10% to 25%, because there are only so many greys the LaserWriter can produce. This is called "banding," and it gets worse the larger the gradient. Assuming this is the problem, the gradient will look much better when output to an imagesetter, due to its greater output resolution (often 2400 dpi or more).

This is why people add noise to a gradient in Photoshop (this doesn't happen automatically) -- to "blur" those large transitions and reduce banding. This does produce a cleaner gradient at low resolutions, but adds to the file size because it prevents compression.

Not that it is that critical, but I wouldn't call 150 a "very high end" screen. 200 might be a high end screen with 300 being very high end.

Most quick print shops go up to 120. We are a small commercial printer and run at 150 lpi routinely. 85 is a pretty coarse screen. I most papers that I have seen run 85 or so. USA Today, if I'm not mistaken, uses a 100 lpi screen. Just depends on the job specs, but there isn't much commercial use for anything below 85 lpi. Customers demand higher and higher quality, and with a higher lpi, the image looks sharper. Just my two cents, FWIW.

Poster: Jae Lynn <Jaelb@AOL.COM>

> Just depends on the job specs, but there isn't much commercial use for
> anything below 85 lpi.

It also depends on the paper. 85 or even 65 lpi for lower grades of newsprint. But for a nice coated stock, a lower grade screen would be ridiculous. the paper wouldn't soak up any ink and a screened picture would look polka dotted.

> In selecting the scanner, my rather primitive thinking was that since
> printers only print to a resolution of what they call "150 lines", that
> was probably equivalent to 150 dpi.

LPI refers to the halftone screen, while (in popular usage) DPI refers to the resolution of the scan. In general terms, you should overscan a bit, so for a 150 lpi halftone, you would scan at 225-300 dpi (more accurately, PPI or pixels per inch). 150 is a very high end line screen, BTW. Most jobs use no more than 120-133, and many use even less. For instance, quick print shops usually handle no more than 85, and newspapers often use even less.

Other Resources on the Net

Most of the material presented here was taken from the MacWorld article "Halftones Demystified" and the resources listed below:

Scanning FAQ http://www.infomedia.net/scan/

PageMaker FAQ http://www.makingpages.org/pagemaker/pm-faq.html

PAGEMAKR list archives http://www.listserv.iupui.edu/archives/pagemakr.html

Scanning, resolutions, tips, etc. http://www.scantips.com

STEPPS -- Stop Tax Exempt Private Property Sprawl -- Framingham