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Old Jul 18, 2006, 5:08 PM   #1
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Ahhh, I've been a fan of Steve's Digicams for several years but, I've just discovered the Qimage forum. I purchased Qimage Pro just a few days ago because I was so impressed by the quality of my prints!

I read the Tech Corner article "Coming to Terms with DPI..." http://www.steves-digicams.com/techc...uary_2005.html

I have a pretty good understanding, but I still need a little help!

I have been scanning some 8 X 10 prints on my Canon 9950 scanner. The actual prints are of good quality. I figure that you probably can't get much more than 300-360 dpi out of a good quality print, but I have been playing it safe and scanning at about 600dpi and also 48 bit output to make sure I get all the information out of the prints. The scanner itself is capable of 1200 dpi (for print scanning).

Since Qimage at it's highest quality setting is Pyramid / Maximum- 720PPI is it best to scan at 300 dpi (and 48 bit) to take full advantage of your advanced interpolation? Or should I keep scanning at 600 to make sure I'm getting all the "real" information out of the print? Or something in between? Hard drive space is not a concern, just quality.

I read in the Qimage manual that you should not interpolate in Photoshop before importing into Qimage which makes total sense (because Qimage has a more advanced interpolation "engine"), but I'm not sure how this applies to importing from a scanned print. (Since I'm not totally sure what the scanner is doing to come up with 1200 dpi out of a print.) It seems that you would just want to get the most information from the print and let Qimage do the rest. So in a nutshell, I'm asking at what dpi do you recommend scanning prints to get maximum print quality from Qimage.
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Old Jul 18, 2006, 10:09 PM   #2
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Here's Mike's response to this question a year or so ago.

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Old Jul 19, 2006, 2:06 AM   #3
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You might want to read this: http://scantips.com/resolut.html He uses a shot taken with a prime fixed focal length (non-zoom) Nikon lens on a tripod and couldn't get improvement over 300 PPI. You might go back to the previous page where he gives an overview. You are just spinning your wheels scanning a color print over 300 PPI. The scanner is just guessing at the intermediate pixels and you could probably do better in Qimage if you need more pixels.
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Old Jul 19, 2006, 11:54 PM   #4
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Thanks for your replies!

Slipe- I read the scantips awhile back. Packed full of information. Actually that's where I came up with scanning prints at 600 dpi.

Here... http://scantips.com/basics08.html
Wayne says "I do routinely scan color prints at 300 dpi, when appropriate for the purpose. If a large image size is needed, like for printing at enlarged size, then I do use 600 dpi, because image size is needed, and that gives size. But I don't kid myself that I get much more detail than 200 or 300 dpi will give. Still, in the chance that some major miracle might somehow occur, then I've got it. <grin>"

DaiButsu- thanks for the link. It sounds like Mike said over a year ago to use 600 DPI to make sure you get all the information from the print.

I guess that hasn't changed any with the current version of Qimage (I don't know if Pyramid interpolation was available then, etc. etc.).

What I'm getting at is if there might be a little more than 300 dpi from a print why not scan at 400 dpi to make sure your getting all the information? It seems that scanning at 600 dpi would be relying a little to heavily on the scanner for interpolation. Isn't the scanners means of interpolation probably inferior to Pyramid interpolation in Qimage?

Or, since Qimage is interpolating my images to 720 dpi for my Epson printer then maybe scanning at 360 dpi would be just right, Then Qimage would be exactly doubling the dpi to 720.

Maybe I'm just being to picky. But hey, you can't fault a guy for just trying to get the job done right.... right? :?

Any further thoughts would be appreciated?
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Old Jul 21, 2006, 6:39 PM   #5
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From what I have read, and seen, most scanners list their DPI as two figures (e.g., 600/1200, 1200/2400, etc. ) The first number represents the actual maximum physical dots-per-inch capability of the scanner along the horizonal axis.The second number is the posible resolution along thevirticle axis (controled by the stepper motor). As long as you scanat the dpi of the first number or even 1/2 or 1/4ofthat value (maybe a minimum or 300 dpi), the scanner I/O driver does not interpolate. However, if you try to scan at any other value, either higher or lower, the driver has to interpolate. The place where you can really run into problems with scanning is in the 'noise reduction' andsharpening setting (e.g., unsharpen mask, etc.). The algorythms used by the different scanner device drivers canvary from good to horrible in these areas.

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Old Jul 22, 2006, 10:21 PM   #6
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Yes, that's kinda what I was trying to find out. I have some vague memory of reading something to that effect on the scantips.com website quite some time ago, but I couldn't find it this time around. Since you mentioned it, I guess I'm not imagining things. I guess I'll look again. In the meanwhile, I think I'll just keep scanning prints at 600dpi to make sure I get all the "real" information, edit, and then let Qimage do it's work for printing.
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