Web Sites used for Resolution Packet (from Ins and Outs of Scanning)
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Outs of Scanning
last modified July 16, 2001
Scanning Pictures and Resolution
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Basic Intro - http://www.scantips.com/basics02.html
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Really, what Resolution? - http://www.scantips.com/basics2f.html
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Resolution Review (sort of) - http://www.scantips.com/basics2i.html
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Image Calculator - http://www.infomedia.net/scan/calcs.html
Scanning for Printer Output
- Basics of Scanning for the Printer - http://home.att.net/~cthames/Printer1.htm
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The Arithmetic of Printing Images - http://www.shortcourses.com/how/resolution/printed.htm
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The Basics of Scanning (what image size do I need) http://graphicssoft.about.com/library/weekly/aa111799p4.htm
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Scaling an Image For Printing - http://www.scantips.com/basics2c.html
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What is Resampling - http://www.scantips.com/basics2e.html
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Finding the Scaling and Resampling Commands in Various Programs - http://www.scantips.com/basics2g.html
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Resolution capability of printers - how much to scan? - http://www.scantips.com/basics3b.html
Scanning for Monitor Output
- Scanning for the Monitor - http://home.att.net/~cthames/monitor1.htm
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Video Resolution - http://www.scantips.com/basics1c.html
Other Thoughts
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Moiré Interference - Scanning images in magazines/books/newspapers - http://www.scantips.com/basics06.html
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More Moiré tips - http://desktoppub.about.com/cs/moire/index.htm
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Aspect Ratio - http://www.scantips.com/basics3e.html
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Photographic Resolution - How much can we scan? - http://www.scantips.com/basics08.html
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Some good scanning and resolution tips - http://www.infomedia.net/scan/
Resolution Tips and Tricks
- While scanning - when creating the image, resolution determines the spacing of the pixel samples taken from the original master copy. If we scan a width of 2 inches at 100 dpi, we create an output image width of 200 pixels. This is basically all resolution does, and then the output device takes over.
- While on video screen - Scanned resolution no longer has any meaning other than size. The image width of 200 pixels will occupy 200 pixel positions on the screen, which might be 640 or 800 pixels wide itself.
- While printing - Resolution is just a remembered number from the original scan, and now it is used to determine the printed spacing of the pixels on the paper. 200 pixels at 100 dpi will print as 2 inches width, same as the size of the scanned original. We can scale it if desired, and print it at 200 dpi, producing a 1 inch width, or as 50 dpi, producing a 4 inch width. But the printer obviously will have a preference for some particular resolution number that's best for its dithering capability. 100 dpi may not look good if the printer wants 200 dpi. Meaning, this image may not be of sufficient size for such scaling. We can print larger than we have data pixels, not good. Or we can swamp the printer with a huge image, causing a flood of excessive pixels for which it has no use, not good either.
- The higher the DPI (Dots Per Inch), once again, the smoother both photographs and line art will appear. When it comes to printers, if you increase the DPI of a graphic, it will remain the same size, but it will look smoother, because more dots are being used to create the graphic.
- Today, 600 DPI is fairly standard for laser printers.
- Your monitor sees everything in pixels per inch. A generic number used to explain what resolution to scan is 72 dpi - this is a general number (see http://www.scantips.com/basics1a.html for more info on what to scan in for monitors).
- What if you changed the resolution of the graphic to 36 PPI? All of the sudden your graphic would be two inches by two inches (36 x 2=72). And if you changed the resolution of your graphic to 144 DPI, your graphic would shrink down to half an inch by half an inch. On the other hand, if you increase the PPI that a graphic will be displayed on a monitor, you'll actually decrease the size of the graphic.
- Higher resolution is usually wasted on the monitor — but it will result in a larger file size, which means a longer download. And you don't want that.
- ANOTHER WAY TO SAY THIS IS - For printers, a 4 x 5 graphic always remains 4 x 5. Increase the graphic's resolution, and you'll be able to display more shades of gray, but the physical size of the graphic remains the same. For display, the size of the graphic is dependent on the resolution of your display device (On video monitors, scan resolution merely determines image size). The higher the resolution of your display device, the smaller your graphic appears. The resolution of the graphic itself doesn't matter to your monitor.
- Today more and more computers are shipping with larger monitors. So what screen resolution should you design for? Always check your graphics at all three of these resolutions (.640 x 480, 800 x 600 and 1024 x 768). Just because most desktop monitors can display at 800 x 600 or higher these days, that doesn't mean they're actually set to that resolution when they're shipped. Often they're left at the default 640 x 480 (even my 21 inch monitor was set at 640 x 480 when it arrived two years ago!). And there are a lot of laptop users out there who can only comfortably display 640 x 480.
- What resolution do you need to scan in at for printing? The general rule of thumb is your scanning resolution dpi= 2 x LPI (The printing industry's term for resolution is lpi (Lines Per Inch), a measure of printed image resolution-like detail. Magazines are typically 133 or 150 lpi, newspapers are typically 85 lpi). If you can find what lpi your printer works at. If not use the following:
- For inkjet or laser printers, here are good scaling guidelines for Color or Gray Scale photographs:
300 or 360 dpi printer - use 60 to 120 dpi image.
600 or 720 dpi printer - use 120 to 240 dpi image.
- Why not scan in at the highest PPI your scanner allows? Won't you get a better photograph? No. Like the Web, the printer won't utilize anything over its capability. And you still technically have to consider download times — to the printer, that is. A larger file will take longer to print.
- What resolution to take pictures at? The default resolution for many cameras is 144 dpi, which is almost enough to print to an inkjet printer. Most inkjet printers have an LPI (lines per inch) of 55-85. Since normally you want two times the LPI for the resolution of your photo when printing, you can see that you'd probably want about 150 DPI. If a standard quality photo is resolution 640 x 512, 144 DPI. To determine how big it will print, just divide the image size by the image resolution (640 ÷ 144 = 4.44; 512 ÷ 144 = 3.56). Therefore, this photo will print out 4.44 x 3.56 inches, maximum. High quality and super high quality photos are 1280 x 1024. Therefore, the largest they'll print out at the default 144 PPI is 8.89 x 7.11 inches.