Level 3

Lesson 4

In this lesson, you will learn the difference between the display size and the print size of an image.

Introduction

In digital photos, images are made out of numerous little squares called “pixels”. Image resolution refers to the amount of information that is stored for an image and is measured in pixels per inch (ppi).

Monitor resolution is the number of dots per inch that a monitor uses to display an image. Monitor resolution is measured in dots per inch (dpi) or pixels per inch (ppi). It determines how large or small the image appears on the screen.

This lesson will show you the display size of an image on the screen.

·   Open file A.

The file opens at 100% zoom level.

·   Go to the “Menu bar”.

·   Choose Image > Image Size.

·   Examine the “Image Size” dialog box.

The image’s print dimensions are 1” x 1”.

The resolution is 72 ppi.

·   Click the [ Close ] button to close the dialog box.

·   Go to the “Menu bar”.

·   Choose View > Rulers.

Rulers will appear along the top and left hand side of the active window, showing that the image is 1” x 1”.

·   Open file B.

The file opens at 100% zoom level. It shows that the dimensions of the image are also 1” x 1”.

·   Examine the “Image Size” dialog box for file B.

The image’s print dimensions are 1” x 1”.

The resolution is 144 ppi.

·   Click the [ Close ] button to close the dialog box.

·   Rest the pointer on the title bar of file B.

The pointer changes to a white arrow.

·   Hold down the mouse button and drag the title bar of file B to the upper right corner of the screen, until it sits beside file A.

·   Compare the two open files.

Though the rulers on the two document windows indicate that both images are 1” x 1”, the display size of file B is much larger than that of file A.

This is because, at 100% zoom level, 1 image pixel = 1 monitor pixel. When the monitor resolution is 72 ppi, only 72 pixels can be displayed in one inch on the monitor.

Hence, file A (72 ppi) fills a 1” x 1” area of the screen, while file B (144 ppi) fills a 2” x 2” area of the screen.

The rulers on the respective document windows reflect the print dimensions of the two files, not their sizes on the screen.

Both images are 1” x 1” in print. We can verify this by printing hardcopies of the two files.

Conclusion

In this lesson we learned that monitor resolution determines the size of a displayed image. If the image resolution is higher than the monitor resolution, the image will appear larger on the screen than it will in print.