Re: Resolution of graphics for printed docs

["Chris Christner" <cchris -at- toptechwriter -dot- us>]

Hi,

I thought I'd answered the OP's question earlier in this thread, but some
of the responses from other posters show that there's still confusion
about printing screen captures.

Let's say you've used a screencap utility to capture an Apple OS 9 print
dialog box. Looking at the image details in Photoshop, you'd see:

- Pixel dimensions: 504 pixels wide by 315 pixels tall
- Print size: 7 inches wide by 4.375 inches high at a resolution of 72
pixels per inch (ppi).

Now, if you wanted to include the capture in a manual for printing, 7 x
4.3 inches would be too big and 72 ppi printing at 300 or 600 dpi would
look too crude, so what to do?

Well, you could simply change the resolution to 150 ppi, which would give
decent results when printed, but the file size would double and you would
still have to reduce the image's size in Quark or InDesign so it would fit
on a page.

A better answer would be to reduce the image's print size while at the
same time increasing its resolution. That way the file size remains the
same while the resolution is increased to print quality. So we'd reduce
the print size by 50% to 3.5 W x 2.1875 H and double the resolution to 150
ppi (it should be 144, but 150's close enough and works better with
printers).

Think about it, when you look at a 72-ppi image, there's no more
information to be had, you're seeing the image at its maximum clarity.
It's like the graphics in a comic book, once you've magnified the image to
to where only the individual dots that make up the image are visible,
there's nothing more to see.

But just as that comic book graphic becomes clearer as you reduce the
magnification (shrinking the image, in effect) if you reduce the size of a
screencap by 50% while doubling the resolution, you've also doubled the
amount of information being displayed, but it's in a smaller space. The
benefits in doing it this way are that all screen captures will be sized
to the same proportions for consistency, and if you view the reduced
images online, they'll still be very readable.

You can get the same effect by importing the 72-ppi image into Quark or
InDesign and sizing it smaller, but pre-flight checks will usually choke
on such images because they show up as 72 ppi even though by reducing
their size they'll probably be printing at 150 dpi or higher.

For more info on printing screencaps try:
http://www.webdevelopersjournal.com/columns/ajs_resolution.html

For an explanation of DPI vs. PPI, go to:
http://www.tildefrugal.net/photo/dpi.php

Hope this helps,
Chris
___________________________________________
TopTechWriter.US
http://www.toptechwriter.us
Award-winning technical writing and illustration services.



John Posada wrote:
> Does your response get him any closer to a solution or any closer to
> allowing us to help him?
> 
> --- "T.W. Smith" <techwordsmith -at- gmail -dot- com> wrote:
> 
> > The app used shouldn't matter. It's all about pixels and color
> > depth.
> > 
> > Now, if you subsequently edit the captures, well then ....
> 
> 
> John Posada

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