what scanning resolution to use for archival of letters?

[sybariten]

Hello fellow videopeople and happy new year.

I am planning to do a lot of scanning of documents, actually formal letters from different places

Do you have any opinions on what DPI i should use? The question is, if i for instance do them all in 300 DPI, would that good enough for printing some of them some other day ?

Frankly i could just throw these away, they are not that important, but i like to feel that i could make a gould representation of them on paper later.

The printer in question then would be some laser printer, i guess.

peace

[thecoalman]

if your scanning a 8 1/2 x 11 inch document 300 dpi is more than sufficient.

[sybariten]

uh, yeah, i forgot to say, the papers will be "A4" size, which for you yanks is very close to "lettersize", i believe. 29.5 cm x 21
Although, in a way i cant see how the physical size of the document should matter, if i am gonna reprint it i still will try to print it in the exact same size that the paper originally was.

[thecoalman]

if i am gonna reprint it i still will try to print it in the exact same size that the paper originally was.

By default yes it should print at the same size you scanned it providing you leave the resolution (dpi) as is.... A 8 1/2 x 11 paper scanned at 300 dpi is a 8.2 meagapixel image, well beyond what you would need to reprint it. http://www.nepadigital.com/bb/viewtopic.php?t=140

[bunyip]

The best format for documents (since they are mostly white space) is compressed TIFF, it is lossless and can reproduce the original perfectly. Usually anything from 100 to 200 bpi is plenty.
And if the document is monochrome or even greyscale then the file size will be quite small.

[rallynavvie]

Actually we scan legal documents to PDF for archival. A lot easier to access that way. We use the B&W printer at work to scan documents in B&W to PDF @300dpi. The full version of Acrobat allows you to create an Acrobat PDF from a scanner (as opposed to a Photoshop PDF which takes up a little more room at that resolution). 300dpi is plenty for our scanner, though I've noticed our color flatbed doesn't do as good a job at the same resolution when scanning B&W or grayscale. I guess it would depend on the scanner then. Scan one at 300 dpi and then print it on something and see if it looks OK.

[sybariten]

Thecoalman:
OK, thanks for the link to your forum post! I think one of the important factors why this area has always been a bit mystified for me, is that i havent been sure whether images have a "built-in" DPI attribute or not.
I think lots of software isnt really explaining that ... or maybe its just me making things more complicated by investigating. Anyhow i think that attribute sounds a bit useless, a picture is a picture, and its made up by a specific dimension of pixels and thats it .... desired printing size could always be given at the stage of printing. Oh, well, whatever.

Bunnyip:
thanks for the point on compression, never thought about that they contain lots of white space, but thats true.
However, in fact space isn't really an issue here. If i can fit one hundred letters on a one-dollar CD, thats fine with me. I'll probably go for compressed tiff, or png.

Rallynavvie:
here's something i've never understood: why do people scan stuff into PDF's ? PDF's are just a hassle, in a way, if you ask me. Sure, they give very great printing results when you download manuals and technical papers and such, but then we are talking about object oriented or structured graphics. Scanning documents should rather give bitmapped images, and whats the point of having those as PDFs ?
I do know that there are quite a few programs that does this though, i may even have some myself. Oh well i guess it isnt considered classy to turn stuff into TIFFs.

peace!

[rallynavvie]

Reason for PDF is it's a standard now like JPEG is. Anyone can go to Adobe and download the free Reader to be able to open and print from almost any platform (Windows, Linux, Mac, more). It is still a bitmap image but at least its print interface is a far sight better than programs meant to handle other formats like TIFF, JPEG, BMP, and so on. You can make multi-page TIFF files but it's a more native feature in Acrobat.

Other thing you may or may not want to consider, especially if all these documents are offset printed or a good clean laser print, is OCR text scanning. When we do legal documents they're generally clean copies printed on a laser printer and obviously don't have access to the original files. However the OCR software (we use OmniPage and an Acrobat plugin) can recognize the text and turn it into text data. In the PDF format this greatly cleans up the text, from OmniPage we can turn the document into a Word file or a few other publishing apps and then can make changes to it. The other handy feature of the clean Acrobat page capture is you can then use search features within the text of the document, handy when going through a DVD full of documents that are named by a simple case number.

[thecoalman]

Anyhow i think that attribute sounds a bit useless, a picture is a picture, and its made up by a specific dimension of pixels and thats it .... desired printing size could always be given at the stage of printing.

It's not completely useless because it sets the default scale of the image in inches and you need it for setting how much detail you want to scan.

Rallynavvie:
here's something i've never understood: why do people scan stuff into PDF's ? PDF's are just a hassle, in a way, if you ask me.

Rally forgot to mention that you can also lock a PDF so it can't be edited....

[ZAPPER]

I save copies of all my job reports and such at 200 by default. They print out better than lets say a fax would. Sometimes I print them to the fax on my PC if I am sending to the general office. I have seen them at the other end and they look fine. If I want them to go straight to someone in person, I print them to PDF with the distiller printer option and E-Mail it direct. The best thing about a PDF is nobody freaks out over a TIFF or differnt file type showing up in their mail and them having to pick an app to open it. Another sneaky thing I like about a PDF is when I send CAD drawings. When the receiver gets it, they can't modify it and put their name on my work. If they want the DWG or whatever CAD file they need to start coughing up cash! :P

[live4ever]

If you have the full Acrobat I'd suggest scanning them to PDF with that. Then you can do an OCR of the PDF and create a searchable layer of text while still having a scanned image visible.

[JSB]

Another sneaky thing I like about a PDF is when I send CAD drawings. When the receiver gets it, they can't modify it and put their name on my work. If they want the DWG or whatever CAD file they need to start coughing up cash! :P

I love when our design firm send me DWG's in PDF form... I just have not figured out how to plot them bigger that legal on our 36" laser potter.

JSB

[ZAPPER]

Another sneaky thing I like about a PDF is when I send CAD drawings. When the receiver gets it, they can't modify it and put their name on my work. If they want the DWG or whatever CAD file they need to start coughing up cash! :P

I love when our design firm send me DWG's in PDF form... I just have not figured out how to plot them bigger that legal on our 36" laser potter.

JSB

You should be able to print them any size you want. I will have to check on how to do it and get back tp you later. But I think that even the Reader version allows for different page sizes.

[rallynavvie]

Depends on the page size specified in the print driver. We have Xerox and Oce oversize B&W printers that contain the usual architectural sizes A-D. Just set the paper size to your desired dimension and then tell Acrobat to enlarge to fit the file to the specified paper size.

[enstg8er]

Actually we scan legal documents to PDF for archival.

agreed. especially useful for tax software. when you finish print>acrobat and save. print paper copies from that as needed, no need to hunt for software to read old tax forms......

[JSB]

Depends on the page size specified in the print driver. We have Xerox and Oce oversize B&W printers that contain the usual architectural sizes A-D. Just set the paper size to your desired dimension and then tell Acrobat to enlarge to fit the file to the specified paper size.

Drivers issue... thats what I was guessing.

My works IT/IS dept had a hell of a time getting our Oce 9400 to work when we switched from Win98c to Win2k. Along with a new DHCP system, they had their hands full.

I will have to call the HELP desk, don't get me started... (I had to write the driver install page for AutoCad 2000i for them) ... and have them start a trouble ticket. I am sure they will jump right on it

JSB

[rallynavvie]

I can't recall which model Oce we've got, either the 9400 or TDS400. Ours works just fine. I'll find out which it is and give you the trick for creating the FTP shortcut for printing PDF files if it's the same one. All you need to know is the IP of the printer.

[sybariten]

I just wanted to say thanks for your input.

I finally settled for 300 DPI mono and greyscale, after doing some qualitative tests. A friend printed some 300 and 600 DPI scans of an electricity bill on his inkjet printer. Well, you can hardly tell any difference at all.

As for file format, i think i'll stick with some bitmap like TIFF. Compressed TIFF gave, as someone suggested, very nice filesizes, although that isnt really an issue here.

As for the ideas on OCR, i have tried it before, but i won't be needing it here. Most of these papers is stuff i would throw away anyway, i'm just making some archives should i ever need to prove something legally or so. And then i guess it'd be more of a problem had i improved the documents....

peace

ps. some of the bigger packages in OCR today, i think it may be called Omnipage office or something, can achieve amazing results, and treats the text very well. It can even read the result into a speech synthesized wave file afterwards. Hell, you can even choose if you want Helga from Germany or Paul from England to read it.[/i]