Publishers of technology books, eBooks, and videos for creative people

# Resolution-related topics in Photoshop CS4

• Print
• + Share This
From the book

## Resolution

Resolution is one of the most widely used and yet least understood words in desktop publishing. People use it when they talk about scanners and printers, images and monitors, and halftones. Then they wonder why they’re confused. Fortunately, it isn’t that hard to sort out all of the different meanings of resolution.

An image in its pure digital state has no physical size—it’s just a bunch of pixels without any real-world measurement attached to them. Resolution answers the question “How small are the tiny squares that make up this picture?” Once you bring an image into the physical world, the number of pixels across the width and height take up a specific amount of physical space in print or on screen, and that determines the resolution.

The resolution of an image is the number of pixels per unit of measurement—usually the number of pixels per inch (ppi) or pixels per centimeter (ppcm). If your image is 72 pixels wide and you tell it to be 72 pixels per inch, then it’s an inch wide. If you print it at half the size, you’ll still have the same number of pixels, but they’ll be crammed into half the space, so each inch will contain 144 pixels, or 144 ppi (see Figure 2-5). Print it at 300 percent of the original size, and the resolution goes down to 24 ppi.

You can look at resolution in another way: If you know an image’s size and resolution, you can figure out its dimensions. When you scan a picture that is 3 inches on each side at 100 pixels per inch, you know that the image has 300 pixels on each side (100 per inch). If you then scan it at 300 pixels per inch, the dimensions shoot up to 900 pixels on each side.

#### How Resolution Changes During Production

One source of confusion is that people often lock onto a single resolution value, like “300 dpi,” and assume that something’s wrong if they don’t see that value from start to finish, but that’s not how it is. It’s useful to think of resolution at various stages of production: sampling resolution, document resolution, effective resolution, and device resolution (see Figure 2-6).

Sampling Resolution. If you’re using a scanner, sampling resolution describes how precisely an image was scanned, in samples per inch (spi). You set the sampling resolution in your scanning software. For digital still and video cameras, “samples per inch” is meaningless—if your camera takes images that are 4256 pixels wide by 2832 pixels tall (12 megapixels), a landscape photo 3 miles wide will produce the same 4256-by-2832-pixel frame as a close-up of a 3-inch-wide flower.

Document Resolution. When you save an image from software such as Photoshop, the resolution value saved into the file is its document resolution. Changing this value doesn’t change the image quality unless the image is resampled at the same time (see “Resampling” later in this chapter). When you don’t resample, a 4256 by 2832 pixel image still has 4256 by 2832 pixels, whether you set it to 72 ppi or 300 ppi, because the total number of pixels in the image doesn’t change. Does this mean that file resolution isn’t important? Not until you start thinking about final output, and at that point it does matter.

Effective Resolution. When you place one document inside another and resize the first document, its pixels may be stretched or compressed. This is its effective resolution—the resolution of the image after it’s been scaled to its final print size. The document resolution inside the file still exists, but the new size changes the density of the pixels.

Device Resolution. Device resolution is the resolution of the final output device. For example, a monitor might have a device resolution of 100 ppi, and a platemaker might be 2400 dpi. This kind of resolution is not stored in the file; in fact, it hardly has anything to do with the file at all.

In printing, the effective resolution of an image typically doesn’t need to be as high as the device resolution. For example, while an inkjet printer might print at 5760 dpi, the optimum image resolution for printing photographic images might be 360 ppi, because printers mix very tiny dots to build larger groupings that form tones and colors. Inkjet printers mix device-resolution ink dots to build areas of color. Printing presses use device-resolution ink dots to build halftone cells; the 2400 dpi dots on such a device may be grouped into halftone cells at 150 lines per inch (lpi), for example.

When you create images for the Web, you don’t know the final device resolution. Someone might view your Web page on a 20-inch desktop monitor at 1680 by 1050 pixels, while another might have a 15-inch desktop monitor at 1024 by 768. There’s only one measurement you can rely on: the image dimensions in pixels, such as 600 by 400 pixels.

• + Share This
• 🔖 Save To Your Account

### Peachpit Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from Peachpit and its family of brands. I can unsubscribe at any time.

## Overview

Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about Peachpit products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

## Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

### Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

### Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

### Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites; develop new products and services; conduct educational research; and for other purposes specified in the survey.

### Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

### Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email ask@peachpit.com.

### Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

### Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

## Other Collection and Use of Information

### Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

### Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

### Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

### Do Not Track

This site currently does not respond to Do Not Track signals.

## Security

Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

## Children

This site is not directed to children under the age of 13.

## Marketing

Pearson may send or direct marketing communications to users, provided that

• Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
• Such marketing is consistent with applicable law and Pearson's legal obligations.
• Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
• Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

## Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

## Choice/Opt-out

Users can always make an informed choice as to whether they should proceed with certain services offered by Adobe Press. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.peachpit.com/u.aspx.

## Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

## Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

## Sharing and Disclosure

Pearson may disclose personal information, as follows:

• As required by law.
• With the consent of the individual (or their parent, if the individual is a minor)
• In response to a subpoena, court order or legal process, to the extent permitted or required by law
• To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
• In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
• To investigate or address actual or suspected fraud or other illegal activities
• To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
• To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
• To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

## Links

This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

## Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

## Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020