Monday, June 25, 2007
JPEG Photos
JPEG (pronounced jay-peg) is the standard format used by digital cameras to store picture files. If you don't need to resize your JPEG originals, you can share them via email or post them on a Web page immediately. All Web browsers and email programs can display JPEG photos. Chances are, though, that your originals are too large for on-screen use, which means that you need to size them smaller. After you take that step - or do any other photo editing - you must resave the file in the JPEG format before sharing it online. (In case you're wondering, JPEG stands for Joint Photographic Experts Group.)
When you save a file in the JPEG format, the picture undergoes lossy compression. This feature creates smaller file sizes by dumping some image data, which can reduce picture quality. So before you save an image in the JPEG format, create a backup copy using a file format that doesn't use lossy compression - TIFF, for example, or the Photoshop Elements format (PSD), if you use that program.
The following steps show you how to use the Photoshop Elements Save for Web utility to save your picture in the JPEG format. Using this feature enables you to see how much damage your picture will suffer at various levels of JPEG compression. If you're using another image editor, check the Help system for the exact commands to use to save to JPEG format. The available JPEG options should be much the same as described here, although you may or may not be able to preview the compression effects on your picture.
To save pictures in JPEG, using Photoshop Elements, follow these steps:
1. Choose File --> Save for Web to display the Save for Web dialog box, shown in Figure 1.
The preview on the left side of the dialog box shows your original picture; the right-side preview shows how your photo will look when saved at the current settings.
Figure 1: The Quality settings determine how much compression is applied.
2. Select JPEG from the Format drop-down list, labeled in Figure 1.
After you select JPEG, you see the other save options shown in the figure.
3. Set the compression amount by using the Quality controls labeled in the figure.
A higher Quality setting results in less compression and a larger file.
The Quality drop-down list offers five general settings: Maximum, Very High, High, Medium, and Low. Maximum provides the best picture quality/least compression; Low provides the least quality/most compression. If you want to get a little more specific, use the Quality slider on the right. You can specify any Quality value from 0 to 100, with 0 giving you the lowest image quality (maximum compression) and 100 the best image quality (least compression).
4. Turn off the Progressive and ICC Profile check boxes.
If you see a check mark in a box, click the box to remove the check mark and turn off the option. Progressive JPEG files generally aren't a good idea, because they take longer to download fully, and some Web browsers don't handle them well. The ICC Profile option has to do with some color management issues that professional imaging folks may want to investigate, but most don't need to worry about. In addition, the option adds to the file size.
5. If your picture contains transparent areas, choose a Matte color.
This feature comes into play only if the bottom layer of your picture contains transparent areas. JPEG files can't preserve transparency, so transparent areas are filled with the color you choose from the Matte drop-down list - white, if you don't select another color.
If you're placing the photo on a Web page that has a solid-colored background, you can make the transparent parts of a JPEG photo appear to retain their transparency. Just match the Matte color to the color of your Web page background. The viewer's eye then can't tell where the image stops and the Web page begins.
6. Click OK.
The Save for Web dialog box disappears, and the Save Optimized As dialog box comes to life. This dialog box works like any file-saving dialog box. Just give your picture a filename and specify where you want to store the file. The correct file format is already selected for you.
7. Click Save or press Enter.
The program saves the JPEG copy of your picture. Your original photo remains open and on-screen. If you want to see the new JPEG version, you have to open that file.
When you save a file in the JPEG format, the picture undergoes lossy compression. This feature creates smaller file sizes by dumping some image data, which can reduce picture quality. So before you save an image in the JPEG format, create a backup copy using a file format that doesn't use lossy compression - TIFF, for example, or the Photoshop Elements format (PSD), if you use that program.
The following steps show you how to use the Photoshop Elements Save for Web utility to save your picture in the JPEG format. Using this feature enables you to see how much damage your picture will suffer at various levels of JPEG compression. If you're using another image editor, check the Help system for the exact commands to use to save to JPEG format. The available JPEG options should be much the same as described here, although you may or may not be able to preview the compression effects on your picture.
To save pictures in JPEG, using Photoshop Elements, follow these steps:
1. Choose File --> Save for Web to display the Save for Web dialog box, shown in Figure 1.
The preview on the left side of the dialog box shows your original picture; the right-side preview shows how your photo will look when saved at the current settings.
Figure 1: The Quality settings determine how much compression is applied.
2. Select JPEG from the Format drop-down list, labeled in Figure 1.
After you select JPEG, you see the other save options shown in the figure.
3. Set the compression amount by using the Quality controls labeled in the figure.
A higher Quality setting results in less compression and a larger file.
The Quality drop-down list offers five general settings: Maximum, Very High, High, Medium, and Low. Maximum provides the best picture quality/least compression; Low provides the least quality/most compression. If you want to get a little more specific, use the Quality slider on the right. You can specify any Quality value from 0 to 100, with 0 giving you the lowest image quality (maximum compression) and 100 the best image quality (least compression).
4. Turn off the Progressive and ICC Profile check boxes.
If you see a check mark in a box, click the box to remove the check mark and turn off the option. Progressive JPEG files generally aren't a good idea, because they take longer to download fully, and some Web browsers don't handle them well. The ICC Profile option has to do with some color management issues that professional imaging folks may want to investigate, but most don't need to worry about. In addition, the option adds to the file size.
5. If your picture contains transparent areas, choose a Matte color.
This feature comes into play only if the bottom layer of your picture contains transparent areas. JPEG files can't preserve transparency, so transparent areas are filled with the color you choose from the Matte drop-down list - white, if you don't select another color.
If you're placing the photo on a Web page that has a solid-colored background, you can make the transparent parts of a JPEG photo appear to retain their transparency. Just match the Matte color to the color of your Web page background. The viewer's eye then can't tell where the image stops and the Web page begins.
6. Click OK.
The Save for Web dialog box disappears, and the Save Optimized As dialog box comes to life. This dialog box works like any file-saving dialog box. Just give your picture a filename and specify where you want to store the file. The correct file format is already selected for you.
7. Click Save or press Enter.
The program saves the JPEG copy of your picture. Your original photo remains open and on-screen. If you want to see the new JPEG version, you have to open that file.
