Image PPI vs. Screen PPI (PPI= Pixels/inch)
Pixel “picture element” and “sub pixel elements “ – the smallest digital display: red, green, blue (RGB).
Your monitor’s PPI is fixed – an LCD has between 67-150 PPI.
Image pixels on paper have no physical size, but pixels on your screen do.
Image PPI only matter when printing onto a non-digital surface.
A 72 PPI or 300 PPI image will appear the same on screen.
Image dimension is also measured in pixels – width and height.
Image dimension affects image file size and not the PPI/DPI.
The DPI/PPI setting only tells the printer how big you want to print the image. If the image is shown on the web, it doesn’t matter.
Less PPI (resolution) means you have more pixels to spread on your non-digital surface (larger print).
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Digital Imagine Tutorial (Spanish and French translation available)
https://www.library.cornell.edu/preservation/tutorial/tutorial_English.pdf
Preface
This tutorial offers base-level information on the use of digital imaging to convert and make accessible cultural heritage materials. It also introduces some concepts advocated by Cornell University Library, in particular the value of benchmarking requirements before undertaking a digital initiative. You will find here up-to-date technical information, formulas, and reality checks, designed to test your level of understanding.
The tutorial can stand on its own, but it is intended to be used in tandem with another product, Moving Theory into Practice: Digital Imaging for Libraries and Archives, by Anne R. Kenney and Oya Y. Rieger (RLG, 2000). This publication picks up where the tutorial leaves off and advocates an integrated approach to digital imaging programs, from selection to access to preservation and management. Over 50 international experts contributed to the intellectual content of this book.
You will note that at certain points within this National Endowment for the Humanities funded tutorial, we invite reader comments and suggestions. In particular, we are aware that the presentation is US-centric, and with your help we seek to augment that perspective to provide a broader international focus. We look forward to hearing from you!
Support for this tutorial comes from the National Endowment for the Humanities. The Spanish translation was funded by the Council on Library and Information Resources. Support for the French translation was received from the Food and Agricultural Organization of the United Nations. No part of this tutorial may be reproduced or transcribed in any form excepting for personal research use without prior written permission of Cornell University Library/Research Department. Requests for reproduction should be directed to the Research Department.
PPI vs. DPI: what’s the difference?
Pixel Perspective: Image vs. Screen Image PPI vs. Screen PPI (PPI= Pixels/inch) Pixel “picture element” and “sub pixel elements “ - the smallest digital display: red, green, blue (RGB).