DPI Recommendation for Images

[Alison Craig]

I have to admit to being curious about this discussion as image quality has never been an issue for me (if it matters: FM9, all patched on Windows 7).

I use only EPS files or, if I need to insert arrows or other highlighted options on an image, I use a TIF or PNG inside a Visio file which I then save to PDF. All images are imported by reference. (I *very* seldom scale a PDF after importing it and if I do, I try to keep it within a few percentage points of 100%.)

I create my final PDFs twice from the same book setup with different joboption files so I get a digital version for viewing and a press quality one for printing on a professional, 600 dpi, high-speed, colour laser (with/without links and lower/higher image downsample settings are the major differences).

Both of these options result in good, onscreen image quality at reasonable zoom levels (if you're going to zoom to 600% or 1000%, you get what you get).

I have to plead major ignorance in the field of images, so how did I luck into a reliable method which I devised after a little trial and error?

Alison


-----Original Message-----
From: framers-bounces at lists.frameusers.com [mailto:framers-bounces at lists.frameusers.com] On Behalf Of Shlomo Perets
Sent: March 25, 2011 3:04 AM
To: framers at lists.frameusers.com
Subject: Re: DPI Recommendation for Images

Alan Litchfield wrote:

>... There is no value that I see in trying to dictate to the reader what
>they will see at any specified zoom. The reader will decide what is
>`good enough' for their viewing pleasure.  ...


Forcing a specific zoom (related to the DPI value at which the screen 
captures are placed in FM) is indeed not practical, especially since 
readers can easily switch between view settings of Fit Page, Fit Width etc. 
(that result in different zoom levels in different computers/screens).

However, this variable zoom effectively guarantees that the rendering of 
screen captures will be suboptimal, with different levels of distortion 
(missing pixels and/or blurred display). This is not a problem when the PDF 
is primarily intended for print purposes, but many PDFs are primarily used 
on-screen (even when the intended use is print, e.g. to benefit from 
interactivity/search).

No easy solutions, unfortunately. Displaying the screen capture without any 
distortion is possible through "off-page" display -- see different examples 
at http://www.microtype.com/ImprovePDF29.html .

[ The same issue applies directly to the display of SWF screen movies 
(where FM8/9/10 only support in-document placement; distortion of movie 
display in the PDF is practically guaranteed), see comparison of playback 
modes at http://www.microtype.com/showcase/MultimediaAsst/PlaybackModes.pdf 
or 
http://www.microtype.com/showcase/MultimediaAsst/PlaybackModes-Native.pdf , 
Acrobat/Reader 9 or higher ]



Shlomo Perets

MicroType, http://www.microtype.com
FrameMaker/TCS training & consulting * FM-to-Acrobat TimeSavers/Assistants



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