1. Technology
Send to a Friend via Email
Getting Started Scanning...
Part 1: Scanning DPI for Email and the Web

When scanning for screen display you need only be concerned with pixel dimensions. A computer monitor displays approximately 96 pixels per inch. For simplicity's sake, I prefer to round this off to 100 ppi. So, if I want an image to appear approximately 1 1/2 by 2 inches on my web page, I would scan it at 150 by 200 pixels. (Continued below...)


 More of this Feature
• Introduction
• Part 1: DPI for Email & Web
• Part 2: Saving Your Scans
• Part 3: Printing Digital Photos & Scans
 
 Related Resources
• Glossary: TWAIN
• Glossary: Resolution
• Digital Imaging & Scanning
• Scanning Tips
• Scanning Software
• Prep Your Photos for the Web
 
 From Other Guides
• The DPI Dilemma
• Scanning Line Art
• Scanning Basics
• Resolution Inch By Inch
 
 Elsewhere on the Web
• A Few Scanning Tips
• DPI for Email & the Web
• DPI for the Monitor
 

When scanning for screen display you need only be concerned with pixel dimensions. A computer monitor displays approximately 96 pixels per inch. For simplicity's sake, I prefer to round this off to 100 ppi. So, if I want an image to appear approximately 1 1/2 by 2 inches on my web page, I would scan it at 150 by 200 pixels.

Each scanning interface is slightly different, but they all should have a resolution setting you can adjust. This will be labeled as either ppi or dpi. You'll want to set the resolution to 96 or 100 and set the dimension units to pixels. Then you can adjust the size percentage values to get the image to the desired pixel dimensions. Whether you adjust the dpi or the percentage does not matter, as long as the values you take into consideration are the output pixel dimensions.

Below is a partial screen capture of my scanner's interface. As you can see, I've set the scanner resolution to 96 dpi, and I've changed the dimensions to pixels. In this example, my image on the screen is going to be approximately 5 inches wide and 3 inches high because these are the values displayed for the final output (the grayed-out values).

Now let's assume I want the image height and width to be displayed at half that size. I can adjust the percentage value to 50%. As you can see below, the input value remains the same, but the output values (the grayed-out values) are 250 by 150, approximately 2 1/2 by 1 1/2 inches, half the dimensions of the image above.

Incidentally, you'll notice that the image file size is reduced to 1/4 of the original... from 439 KB to 110 KB in this example. This is because the total area of the image -- or the total number of pixels in the image -- has been reduced by one-fourth. As you can see, reducing the dimensions of an image can dramatically impact its file size and download time. For this reason, it's important that images you plan to transmit via email and the Web be cropped and sized appropriately. For more information on getting images ready for the Web, see my article entitled Prep Your Photos for the Web.

 Join the Discussion
"Always keep in mind what you are going to be using the scan for and plan for it. You will get a better scan than if you scan it at 4x6 and then say print 8x10."
- COMPUTERCREA

To review:

  • Use no more than 100 dpi/ppi when scanning for screen display
  • Measure dimensions in pixels
  • 100 pixels on screen is approximately one inch

--> Continue to Part 2: Saving Your Scans

Further Reading...

DPI for E-mail & Web
This page explains the best dpi setting and format to use when sending your scanned images over e-mail, or when displaying them on the web.

DPI for the Monitor
What DPI should you use for images you are scanning for viewing on a monitor? Find out here.

Prep Your Photos for the Web
Learn how to rotate, crop, resize, and batch process your pictures with tips and step-by-step instructions for Photoshop, Photo-Paint, Paint Shop Pro, and PhotoImpact.

More About Scanning

Questions? Comments? Post to the Forum!

You can opt-out at any time. Please refer to our privacy policy for contact information.

Discuss in my forum

©2014 About.com. All rights reserved.