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I am trying to figure out the most efficient method for editing raw scanned documents so they look best at 72PPI when published on a website. I have an example here which is from a 600DPI source scan. I have already applied a Gaussian Blur onto both images.

This 1st graphic is resized using Image -> Image Size... where I merely updated the DPI from 600 down to 200. This auto-resized the image dimensions from 800x560 down to 269x187... and you can't really see the dots anymore, but the graphic is much smaller than the original.

graphic01

Now here is a sample of the raw image which I basically copied from a 600DPI doc into a new doc(same dimensions) at 72PPI. It looks exactly the same, and the dots are still very noticeable. Here is a shot from the 600PPI copied into a 72PPI document:

graphic02

I am wondering why the difference between 600 and 72 isn't noticeable when copied over into a new doc, but when rescaled it does appear much smaller and smoother?

And to finish my question, is the "native" size for this image always going to be way smaller than the original scan? Meaning no matter if I scanned at 300DPI, 600DPI, or 1200DPI it's always going to look the same when rescaled down at 72PPI? The bigger graphic above simply has way too many dots and I don't see any possible way to clean it up and still keep the dimensions 800x560.

If I can clarify anything else please let me know. I've been struggling with this for a while so any help would be more than appreciated!

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personally I would re-size the scan to the required size and dpi, then trace it in photoshop recreating the image. –  MephistonX Mar 23 '13 at 18:34
    
@MephistonX I know about the trace feature in Adobe Illustrator but have never heard of this in Photoshop. Does it turn the graphic into a vector? I will definitely look into it if I can find stuff in Google. –  Jake Rocheleau Mar 23 '13 at 19:58
    
no i wasnt thinking of that - i meant using the brushes and tools within photoshop to trace the image –  MephistonX Mar 23 '13 at 21:41

1 Answer 1

up vote 2 down vote accepted

Your first example is clearer and sharper just because it is scaled down, anytime you reduce the size of a graphic it increases the clarity of it.

As far as why nothing changed between the 600 and 72 PPI photos, they both still have the same number of pixels, when you go to print them, there will be a very big difference in their sizes... the 72ppi image may be 11 inches wide while the 600ppi image would be something like 1 inches wide.

This is answered more fully here: Inept knowledge about dpi and ppi,please help?

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Thanks I have been reading and it'll take some practice to understand. Just curious if you have an answer to this follow-up question: no matter if I scanned at 300DPI, 600DPI, or 1200DPI it's always going to look the same when rescaled down at 72PPI? –  Jake Rocheleau Mar 25 '13 at 16:15
1  
Yes, there really would be no reason to scan it at any higher resolution than 300 if you're only going to use it at 72. You'll likely get a cleaner image by scaling it down in Ps from 300 rather that scanning it at 72... but I don't see any reason to scan it at any higher resolution than that. –  Circle B Mar 25 '13 at 19:58

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