tailieunhanh - How to Do Everything With Your Scanner- P15
How to Do Everything With Your Scanner- P15: My thanks to the terrifically creative and knowledgeable staff at Osborne, particularly acquisitions editor Megg Bonar and acquisitions coordinator Alissa Larson for their responsiveness and flexibility. Special thanks to technical editor Steve Bain, not only for his insight and attentiveness to accuracy, but also for actively coming up with many ideas for content. | 54 How to Do Everything with Your Scanner Why Different Images Require Different dpi Knowing a little bit about what different image types are and why they require different resolutions can help you shop for the scanner capabilities you need and keep you from being sold on the ones you don t need. Web images Images you email are stored as JPEG or GIF files and generally require a lower resolution. You can learn more about different file types in Chapter 8. The capabilities of the monitor usually a range of 800x600 to 1024x768 mean that you can t see a difference on screen by using the higher resolution. Scanning at a lower resolution keeps image files small so they travel across the Web quickly. If the recipient plans on printing images however you should patiently scan at a higher resolution. Standard-size color pictures Photos you plan to reproduce at the size you ve scanned require about 300-600 ppi. Added detail at higher resolutions is usually not apparent to the naked eye. Black-and-white photos These can be scanned at a slightly lower resolution than color photos with good results. Enlarged and edited photos If you re going to enlarge photos you want to try to scan them at about twice the normal resolution 600x1200 to avoid pixel spread which makes the photo look grainy. This effect results when the same number of pixels per inch needs to be spread over a larger area increasing the amount of space between pixels. The solution is to add more pixels per inch with higher resolution. Line art Line art is a nonphotographic image. Drawings and blueprints are examples. Usually line art is black and white but it can also be reproduced from a color original. Here you want a relatively high resolution not to capture color but to ensure the sharpness of the lines and detail created with the lines. Slides and negatives These types of media capture far more color data than ordinary paper and you need high-resolution capability to capture it at least 1 200 dpi. Text .
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