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Old Nov 21, 2012, 01:14 AM   #1
kylera
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Best DPI for scanning textbooks?

I'm about to return to school soon, and I intend to have my textbooks scanned. What would be the best DPI to have the book scanned for OCR and reading through a Retina iPad? Space is no issue.
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Old Nov 21, 2012, 03:23 PM   #2
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Print Standard

300 dpi is usually the standard for print jobs. If you can get 300 or higher on your scanner, no more than 600, I'd say go for it. Just don't go too high, because too much detail can really bring out the imperfections of the page, and could cause the file size to be gigantic. Hope this helps!
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Old Nov 21, 2012, 06:59 PM   #3
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Originally Posted by mxbykr99 View Post
300 dpi is usually the standard for print jobs. If you can get 300 or higher on your scanner, no more than 600, I'd say go for it. Just don't go too high, because too much detail can really bring out the imperfections of the page, and could cause the file size to be gigantic. Hope this helps!
So 300 at a minimum but 600 if possible, right? Thanks!
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Old Nov 21, 2012, 10:12 PM   #4
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Originally Posted by kylera View Post
I'm about to return to school soon, and I intend to have my textbooks scanned. What would be the best DPI to have the book scanned for OCR and reading through a Retina iPad? Space is no issue.
Don't be fooled by "DPI" which is used for printing. With a Retina iPad, your concern is getting the correct size which is 2048x1536. If your image is 300 DPI or 72 DPI, it will not matter as long as the image is 2048x1536. If you ever want or think you might need to print a page, then DPI becomes very important. But anything over 300 DPI is a waste.

Case in point, I'm making a casual iPad app game for kids with ADHD. I've using a couple of different programs for many of the screen images. If I render a frame in Lightwave or Vue xStream there is no difference in how the image looks if the image is 264 DPI or 72 DPI so long as the image is 2048x1536.
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Old Nov 22, 2012, 12:45 AM   #5
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Don't be fooled by "DPI" which is used for printing. With a Retina iPad, your concern is getting the correct size which is 2048x1536. If your image is 300 DPI or 72 DPI, it will not matter as long as the image is 2048x1536. If you ever want or think you might need to print a page, then DPI becomes very important. But anything over 300 DPI is a waste.

Case in point, I'm making a casual iPad app game for kids with ADHD. I've using a couple of different programs for many of the screen images. If I render a frame in Lightwave or Vue xStream there is no difference in how the image looks if the image is 264 DPI or 72 DPI so long as the image is 2048x1536.
Excuse my ignorance in this matter, but does that mean that for example, an image sized 100px by 100px of 300DPI and another image of the same size at 72DPI will both equally look like crap when zoomed into?
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Old Nov 22, 2012, 12:56 AM   #6
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Excuse my ignorance in this matter, but does that mean that for example, an image sized 100px by 100px of 300DPI and another image of the same size at 72DPI will both equally look like crap when zoomed into?
DPI = Dots Per Inch

When your printer prints a page, it sprays dots of ink onto the paper. The closer the dots are together, the clearer and more-detailed the image becomes. That is where DPI steps in. 300 dots of ink, per square inch, is better-quality than 72 dots of ink per square inch.

100x100 px will always be 100x100 px on a computer screen, no matter what DPI it is.
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Old Nov 22, 2012, 03:53 AM   #7
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DPI = Dots Per Inch

When your printer prints a page, it sprays dots of ink onto the paper. The closer the dots are together, the clearer and more-detailed the image becomes. That is where DPI steps in. 300 dots of ink, per square inch, is better-quality than 72 dots of ink per square inch.

100x100 px will always be 100x100 px on a computer screen, no matter what DPI it is.
So DPI is only an issue when it comes to printing, but not so much for reading on screen then? The final FILE RESOLUTION is what I need to pay attention to, right?

I also just realized, if a page is properly scanned, I wouldn't encounter issues with zooming into text, right? Unless everything was somehow made into a raster image...
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Last edited by kylera; Nov 22, 2012 at 04:02 AM.
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Old Nov 22, 2012, 11:46 PM   #8
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Originally Posted by kylera View Post
So DPI is only an issue when it comes to printing, but not so much for reading on screen then? The final FILE RESOLUTION is what I need to pay attention to, right?

I also just realized, if a page is properly scanned, I wouldn't encounter issues with zooming into text, right? Unless everything was somehow made into a raster image...
Depends on how deep you want to zoom in without losing quality. Make some test scans, put them on your iPad, zoom in, and see which you think works best. If you don't care for file sizes, just scan at the highest resolution possible, or so. You can always downscale later.

Also, I've never heard of a "non-raster" scanner...
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Old Nov 23, 2012, 12:25 AM   #9
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Originally Posted by kylera View Post
So DPI is only an issue when it comes to printing, but not so much for reading on screen then? The final FILE RESOLUTION is what I need to pay attention to, right?

I also just realized, if a page is properly scanned, I wouldn't encounter issues with zooming into text, right? Unless everything was somehow made into a raster image...
Pretty much correct. And rather than using OCR, you might want to experiment with scanning as a PNG or JPG file (no color, of course).
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Old Nov 25, 2012, 08:55 PM   #10
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150-300dpi.

72dpi if it's for the screen.

If you're scanning textbooks, 150dpi is fine and you can have Acrobat convert it to text via OCR (searchable, copiable).
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