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Scanning Procedure - Resizing
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PostPosted: Fri Dec 11, 2009 5:44 pm    Post subject: Scanning Procedure - Resizing Reply with quote
I've been using my Canoscan 700f for about a year now. I've been really pleased with its performance for 35mm negatives (but now that I have a kiev 60, I'm rather angry with myself that I didn't get one that could do 120 film). But to the point: I have always scanned my images as 2600x3900 resolution, 48-bit, tiff files to begin with. The Canoscan can potentially scan at 9600x9600 which results in an enormous file. Is there any advantage to scanning at this resolution and resizing later in pp? Or is it actually a disadvantage? Many thanks in advance!

~Marc


PostPosted: Fri Dec 11, 2009 6:00 pm    Post subject: Reply with quote
Is that resolution, real or interpolated?
If interpolated, no advantage.
You should scan at maximum optical resolution, then size down as necessary.

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PostPosted: Fri Dec 11, 2009 6:49 pm    Post subject: Reply with quote
According to the specs that Canon gives: 9600x9600 is the optical resolution. This is specifically for the film scanning part. The flatbed offers 4800x4800. Interpolated is rated at 19200x19200. Thanks Orio!


PostPosted: Fri Dec 11, 2009 6:56 pm    Post subject: Reply with quote
Unfortunately, most, if not all, flatbed scanner makers overstate their scanners' maximum resolution abilities. I think you will find that the only difference between 2400, 3200, 4800 and higher is the size of their files.

I own an Epson 4990, which has a claimed max resolution of 4800 ppi, but its actual resolution is closer to 2000 ppi. The only real advantage I've found to scanning at higher resolutions is that I can have prints made at larger sizes before pixelation occurs. I also owned briefly an HP that also had a claimed 4800 ppi, and its true resolution was actually quite a bit lower than my Epson's.

So the only real advantage to scanning at the higher resolutions with your Canon is likely to be that you can have images printed in larger sizes before pixelation occurs. And even then, upsizing scans done at lower resolutions in Photoshop or equivalent will likely provide you with an equivalent image.


PostPosted: Fri Dec 11, 2009 7:08 pm    Post subject: Reply with quote
I have the Epson 4490 and my experience is that I get better image quality if I scan at 4800 and resize, than if I scan at 2400.


PostPosted: Fri Dec 11, 2009 8:36 pm    Post subject: Reply with quote
Orio wrote:
I have the Epson 4490 and my experience is that I get better image quality if I scan at 4800 and resize, than if I scan at 2400.


Both the 4490 and the 4990 have a claimed max optical resolution of 4800x9600. I have found in my testing that in the 9600 direction, my 4990 is scanning at an actual 2800 ppi or so. So it could be that this is what you're seeing.

Here's a link to a thread I started at the HybridPhoto forum regarding this specific topic:

http://www.hybridphoto.com/forums/showthread.php?t=1461

If you aren't a member you might have to join, but it's a good site, so it's worth it. On page two of this thread, Marco B describes how to test a scanner for maximum resolution. This is the method I used. I'd be interested in the results you get with your 4490.


PostPosted: Fri Dec 11, 2009 9:37 pm    Post subject: Reply with quote
Perhaps I am blind but I didn't see any difference on my Epson V500 if I did scan images above 2400 dpi.
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