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Old Jul 4, 2003, 3:14 PM   #1
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Default Scanning Tricks

I need to scan some large photos using a good but not great scanner. I can't get the negivtive, so this is my only choice. I have seen some programs online that you take a group of digital pictures of the same subject with different exposures, and combine them in photoshop to get better lattitude. Will this work with scans? Can I take 5 scans, in varous steps of under/over exposure, and combine them into one with a greater lattitude than the scanner normailly allows? Does anyone know of a shareware program. or photoshop plug in that I can use?

I forgot where I red about the program or its name.
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Old Jul 4, 2003, 4:44 PM   #2
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Once a picture is scanned in, it's a file. The computer doesn't have a clue where the file came from... camera or scanner. You can photo stitch the pictures together into panoramas or even mosaics. Point your web browser to photostitch. There are lots of good ones out there, but can't speak for free ones. If you have Photoshop Elements, that will do it as well as cropping, touching up, etc.

Once you have the consolidated pictures, you'll need to figure out a way to print them. Wide carriage inkjets will do nice 13 X 19s. Your original post said "large pictures". That may not be large enough.
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Old Jul 4, 2003, 6:21 PM   #3
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Don't under estimate how much memory and processing power you will need. At some point your pc will be holding all 5 scans in memory, together with an undo copy and then expect to work on the sum of pics and prepare the printout as one file.
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Old Jul 4, 2003, 11:02 PM   #4
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I have a computer with 1 gig of ram, and a RAID array hard drive. I guess I should be clearer. I have an 8x10 portrait. at 1200 DPI it will be a huge file. I want to scan it 5 times or so. Each scan will be at different exposures. Some exposures will capture the hightlights, others the midtones, and others the dark area's. I want to combine them using a software product that I read about but cant remember that would allow me to combine the scans into one file will alot better dynamic range.

If my theroy is correct, this would be a great way to get better quality out of a flat bed scanner.
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Old Jul 4, 2003, 11:16 PM   #5
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You really only need to scan the photo once.
You can then manipulate the file as many different ways as you wish in an image editing application, saving the image under a different filename each time.
You can then combine those image files again in the image editing application in any way you wish.
To some degree you will be able to duplicate the technique of multiple shots of the same scene using different exposures and combining them later in an image editor.
I suggest you do some research on the various techniques involved or just experiment, all it takes really is imagination, time and practice.
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Old Jul 4, 2003, 11:22 PM   #6
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[quote="Richard Howes"]You really only need to scan the photo once.
You can then manipulate the file as many different ways as you wish in an image editing application, saving the image under a different filename each time.

All scanners have a limited latitude. Latitude is how many shades of brightness the scanner can accurately record. If you over expose a scan, you can bring out details in the shadows. If you under expose a scan, you bring out details in the highlights. Most flat bed scanners cant do both well at the same time.

Im hoping to trick the scanner into performing a higher latitude scan.
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Old Jul 5, 2003, 4:22 AM   #7
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Quote:
"Don't under estimate how much memory and processing power you will need"
As I said, each image will be 1.1Gbyte, you've got 5 of them to merge, so that's 5.6Gbyte plus the undo copies that's 10 Gbyte in memory or disk cached and Photoshop or something else has to process that lot in separate passes! Faster cryogenic cooled CPU's aren't readily available yet.

Since your inkjet printer is probably one of those Epsons with virtually no onboard buffer memory, your printer spool file from a 1.1Gbyte image file will be HUGE as well.

So if you have to start thinking that each scan can realistically be at 300dpi or less. Is one 10X8 scanned in a single pass at 1200dpi going to be better or worse than 5 scans each at 300dpi and merged for more contrast range?

There is a solution, and that's a clever program that scans and saves the top and bottom 10% or so of highlight/lowlight info only on each scan pass at different brightness settings and merges this smaller data set. Now that might be realistic.
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