CHAPTER 5 INTRODUCTION TO IMAGE EDITING Canvas has all the features of a dedicated image-editing program. You can create image compositions, retouch photos, color correct scanned images, or paint your own images. In this lesson, you’ll learn •   basic image terminology •   how to place and crop paint objects •   how to change the color mode of a paint object •   how to apply transparency effects Basic image terminology Paint objects, also called image, bitmap, or raster objects, are com- posed of small squares called pixels. Every paint object has a specific “resolution,” defined as the number of pixels per inch (ppi). In general, an image with a high resolution has more detail, but will also have a large file size. Likewise, a low- resolution image contains less data, so it has lower quality but also a smaller file size. As you get more experienced with images, you’ll learn what resolu- tion is best suited to your purposes. Choosing a resolution When deciding on a resolution for paint objects, it is important to know the medium in which your final project will be displayed. •   For Web work or for displaying images only on screen, 72 ppi is the standard. •   To achieve good results for printing, 150 to 300 ppi is stan- dard (depending on halftone screen frequency). File sizes at high resolution can be quite large. You might find that lower resolution is adequate for laser or inkjet output. •   Very high resolution (above 300 ppi) is needed only for images such as fine line art that will be output to film for commercial printing. For this lesson, we will be working with images at 72 ppi resolution.
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