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

# Understand How Color Works in Photoshop

• Print
Computers know nothing about images, or tone, color, truth, beauty, or art. They're just very complicated adding machines that crunch numbers. Fortunately, you don't have to learn hexadecimal or binary math to use Photoshop, but unless you like heavily pixellated output and wildly unpredictable color shifts, you really want to understand the essential lessons about images that authors Bruce Fraser and David Blatner lay out in this chapter.
This chapter is from the book

### This chapter is from the book 

Computers know nothing about images, or tone, color, truth, beauty, or art. They're just very complicated adding machines that crunch numbers. Every piece of data we store on a computer is comprised of numbers. All the commands we send to the computer are translated into numbers. Even this text that I'm typing is made up of numbers.

Fortunately, you don't have to learn hexadecimal or binary math to use Photoshop—we're living math-challenged proof of that—but if you want to put Photoshop under your control, rather than flailing around and occasionally getting good results by happy accident, you do need to understand the basic concepts that Photoshop and other image editors use to represent photographs using numbers.

We'll keep it simple and equation-free (the computer does the math for you), but unless you like heavily pixellated output and wildly unpredictable color shifts, you really want to understand the essential lessons about images that we lay out in this chapter.

## Pixels and Paths

When you get down to the nitty-gritty, there are essentially two ways to make computers display pictures. In Photoshop terminology, the distinction is between pixels and paths. Other terms you may hear are "raster" (rasters are rows or lines, not reggae) and "vector." We call the stuff made up of pixels "images" and the stuff made of vectors "artwork."

#### Pixel-based images

Images are simply collections of dots (we call them pixels or sample points) laid out in a big grid. The pixels can be different colors, and the number of pixels can vary. No matter what the picture is—whether it's a modernist painting of a giraffe or a photograph of your mother—it's always described using lots of pixels. This is the only way to represent the fine detail and subtle gradations of photorealistic images.

Just about every image comes from one of three sources: capture devices (such as scanners, digital cameras, or video cameras), painting and image-editing programs (such as Photoshop), or screen-capture programs (like Snapz Pro, the operating system, and a host of others). If you create a document with any of these tools, it's an image.

#### Vector artwork

Vector artwork, also known as object-oriented graphics, is both more complex and more simple than a pixel-based image. On the one hand, instead of describing a rectangle with thousands (or millions) of dots, vector graphics just say, "Draw a rectangle this big and put it here." Clearly, this is a much more efficient and space-saving method for describing some kinds of art. Vector graphics can include many different types of objects, including lines, boxes, circles, curves, polygons, and text blocks. And all those items can have a variety of attributes—line weight, type formatting, fill color, graduated fills, and so on.

To use an analogy, vector graphics are like directions saying, "Go three blocks down the street, turn left at the 7-11, and go another five blocks," while pixel-based images are more like saying, "Take a step. Now take another step. And another...." At its core, Photoshop is a tool for working with pixels, but each iteration has offered more support for incorporating vector elements that retain their object-oriented characteristics, such as shapes or type, and you can also use vector elements as selections and masks on pixel-based images.

Outside Photoshop, vector graphics come from two primary sources: drawing programs (such as Adobe Illustrator), and computer-aided design (CAD) programs. You might also get vector artwork from other programs, such as a program that makes graphs.

#### Crossing the line

The distinction between images and artwork occasionally gets fuzzy, because vector artwork can include pixel-based images as objects in their own right. For instance, you can put a digital camera capture into an Adobe Illustrator illustration. The image acts like an object on the page, much like a rectangle or oval. You can rotate it, warp it, and scale it, but you can't go into the image and change the pixels.

A vector artwork file may include a pixel-based image as its only object. In this situation, the file is an image that you can open for editing in a painting or pixel-editing application. Photoshop's PDF (Portable Document Format) files are good examples of this. While PDF is typically a vector file format, you can create a pixel-only PDF in Photoshop.

Just to round out the confusion, Photoshop lets you include vector elements in pixel-based images, either as stand-alone objects (like text) or as clipping paths. A clipping path in an image is invisible; it acts as a cookie cutter, allowing you to produce irregularly shaped images such as the silhouetted product shots you often see in ads (see "Clipping Paths" in Chapter 12, Essential Image Techniques).

• 🔖 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.

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.

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.

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.