(Shelly Cashman Series) Gary B. Shelly, H. Albert Napier, Ollie N. Rivers-Web design_ introductory concepts and techniques -Cengage Learning (2008)

150 Chapter 5 Typography and Images
Figure 5-19 illustrates the Adobe Photoshop CS3 Save for Web and Devices dialog box
with four quality settings of the same JPEG image: Very High, High, Medium, and Low
quality settings. Figure 5-20 summarizes the file size, estimated download speed, and
quality value for each of the four quality settings.
Very High quality
setting
file format
and
compression
options
Medium quality
setting
High quality
setting
Low quality
setting
file size, download speed, and
image quality values
Figure 5-19 Image editing software packages, such as Adobe Photoshop
CS3, contain features to help you optimize your image files
for size and quality.
JPEG Compression and Image Quality Comparison
Image # Quality Setting File Size Download Speed
@28.8Kbps
Quality Value
1 Very High 116.5K 42 seconds 80 quality
2 High 71.68K 26 seconds 60 quality
3 Medium 37.89K 14 seconds 30 quality
4 Low 23.18K 9 seconds 10 quality
Figure 5-20 The relationship between file size, estimated download speed, and image quality can be
previewed in the Adobe Photoshop CS3 Save for Web and Devices dialog box.
Image editing software provides the capability to refine and optimize any image —
whether from a digital camera, scanned from a photograph, created with illustration
software, or purchased from a business that sells predesigned images.