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Resizing TIFF images

Posted on 1998-05-15
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Last Modified: 2013-11-19
A 3" by 5" b&w photo is scanned using a HP 4C flat bed scanner at 300 dpi resolution.  The file is printed using Corel Photo Paint 5 on a Fargo Primera Pro printer.   The print is acceptable at an image size of 3" by 5".  I want to increase the image size to 8" by 10".  How do we increase the image size without it becomming pixelated?  We have tried increasing the scan greater than 100% and scanning at up to 600 dpi without success. Also tried various smoothing routines but we need a very sharp image.  Any ideas?
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Question by:SAGEM
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Expert Comment

by:jbrugman
ID: 1112652
try to increase the size of the file and the reolution, so the software interpolates the nearest colors to keep it sharp.
for example, make it 8" at 10" with 300 dpi resolution. On this moment i think, when you enlarge the picture, the dpi drops down to approx. 120 dpi.
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Expert Comment

by:airbird
ID: 1112653
The number of pixels displayed per unit of length in an image is called the image resolution, usually measured in pixels per inch (ppi). An image with a high resolution contains more, and therefore smaller, pixels than an image of the same dimensions with a low resolution. For example, a 1-inch-by-1-inch image with a resolution of 72 ppi contains a total of 5184 pixels (72 pixels wide x 72 pixels high = 5184). The same image with a resolution of 300 ppi would contain a total of 90,000 much smaller pixels.

Because they use more pixels to represent each unit of area, higher-resolution images can usually reproduce more detail and subtle color transitions when printed than lower-resolution images. However, once an image has been scanned or created at a given resolution, increasing the resolution in Photoshop will not usually improve the image quality because in this case, Photoshop must in effect spread the same pixel information across a greater number of pixels.
The proper image resolution to use for an image depends on how you intend to display or distribute the image. Using too low a resolution for a printed image results in pixelation—large pixels that produce very coarse-looking output. Using too high a resolution (i.e., pixels smaller that what an output device can reproduce) increases the file size unnecessarily and may increase the time required to print or distribute the image. See Screen frequency and image resolution for guidelines on choosing an image resolution.
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Expert Comment

by:airbird
ID: 1112654
The number of pixels displayed per unit of length in an image is called the image resolution, usually measured in pixels per inch (ppi). An image with a high resolution contains more, and therefore smaller, pixels than an image of the same dimensions with a low resolution. For example, a 1-inch-by-1-inch image with a resolution of 72 ppi contains a total of 5184 pixels (72 pixels wide x 72 pixels high = 5184). The same image with a resolution of 300 ppi would contain a total of 90,000 much smaller pixels.

Because they use more pixels to represent each unit of area, higher-resolution images can usually reproduce more detail and subtle color transitions when printed than lower-resolution images. However, once an image has been scanned or created at a given resolution, increasing the resolution in Photoshop will not usually improve the image quality because in this case, Photoshop must in effect spread the same pixel information across a greater number of pixels.
The proper image resolution to use for an image depends on how you intend to display or distribute the image. Using too low a resolution for a printed image results in pixelation—large pixels that produce very coarse-looking output. Using too high a resolution (i.e., pixels smaller that what an output device can reproduce) increases the file size unnecessarily and may increase the time required to print or distribute the image. See Screen frequency and image resolution for guidelines on choosing an image resolution.
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Accepted Solution

by:
aetheros earned 100 total points
ID: 1112655
I take it you are going to crop the image (since 3x5 is not the same proportion as 8x10).



I am not familiar with that scanner's resolution, but if its maximum resolution is 600, you will not be able to enlarge the scan while scanning at 600 DPI.



All you have to do is scan it at 600 DPI. When you double the size of the image, you halve its resolution, so it would be a 300 DPI image. I know you said you tried something along those lines, but setting the percentage at higher than 100% may have been what held you up.



To go from 3x5 to 8x10 is more than 200 percent, though. To get that size, you'll have to enlarge it  266.6% which will end up at 8x13.3.  You'd actually have to scan it at 798 DPI to be able to enlarge it  and keep it at 300 DPI. If your scanner cannot scan that high, you will have to go to a service bureau or a Kinko's.
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