This article is intended to help you determine the best system for a project involving digitizing a relatively high volume of documents.
1. Scanning speed
Most of the times when we are presenting a solution to a client, there is one question that always pops up: "What is the speed of your scanner?" Almost everyone thinks that higher the speed of the scanner, the higher the output. Well, my personal opinion is that it is not so all the times. Beyond a certain level, the scanner will be idle due to the inability to feed documents at that speed, especially when scanning mixed documents. If the documents are different sizes, it is not possible to use the scanner at full speed.
The scanning speed is measured either in ppm (pages per minute) for simplex scanners or ipm (images per minute) for duplex scanners. Today there are scanners ranging from 20 ppm to 200 ppm. Unless the application is for a service bureau (or a similar operation of scanning very high volumes of the same document type) I prefer a scanner in the range of 40 ppm or below.
2. Document size (max & min)
One of the main factors that determines the price of a scanner is the maximum size of a document that can be scanned. Generally there are scanners which can scan either up to
*A4 / legal
*larger than A3
Most of the documents that we get are either in A4 or legal size. But in practice I prefer to go for a A3 scanner, since there are lot of non standard size documents. (I wrote a separate post about the importance of document sizes here.)
Also there are few scanners that can scan extra long documents such as
Production scanners come either with the Auto feeder only or with the flatbed. Some new scanner models (like Kodak 1400 series) have a detachable flatbed which could be very ergonomic depending on the work layout.
A flatbed is required if you need to scan bound documents, books, fragile or very delicate documents as well as files without separating papers etc. Especially when it comes to scanning of legal documents such as contracts or deeds a flatbed is required since these come in double legal size and cannot be separated.
Unless if you are specifically going to scan single sided documents, it is always better to go for a duplex scanner.
5. Scanning Mode - Colour / B&W
There are 3 main output formats in document scanning:
*B&W / bitonal
Most of today's scanners can scan in all three formats. However there could be models that do not support colour scanning. (One such model is Kodak file master, a book scanner that cannot scan in colour; I think this has been discontinued now.)
Also there are some scanners (Kodak i150 and most of others) that support dual stream outputs; that is it can scan a colour document and save two images in two formats at the same time, e.g. B&W and colour.
When it comes to selecting a scanner, (especially for high quality scanning) resolution is a main factor. There are two resolutions to consider.
1. Optical resolution: This represents the actual scanning resolution the scanner is capable of scanning. So this is the important measurement.
2. Output resolution: This is the enhanced or the maximum resolution that the scanner can produce using interpolation. Output resolution is always greater than the optical resolution. It does not add more resolution but just enlarges the image by adding extra pixels artificially. So this is not as important a measurement as the optical resolution.
(This article on scantips.com gives a detailed explanation on image interpolation.)
7. Drivers and capture software
Any of today's scanners come bundled with one or several scanning applications and drivers. There are few things to consider here.
*Drivers : there are two main sets of drivers: Twain and ISIS. Twain is an open and freely available set of drivers intended for consumer level scanners. ISIS is a proprietary standard recommended for high speed production scanners. Most scanners support both drivers. However if you intend to use a separate specialised capture application instead of the one that comes with the scanner, you need to check on the driver compatibility. As an example the recently introduced capture tool Kofax Desktop works with Twain drivers only. Also the famous scan snap series by Fujitsu does not support both these drivers and works on a scan snap specific driver only.
*Output formats: The combination of the scanner and the capture application will decide what are the file types (TIFF, PDF, PDF/A, etc) that can be produced.
*Image enhancements: There are interesting and very useful image enhancement features associated with different scanners. A good example is the "perfect page" feature in Kodak scanners. (pdf perfect page matrix)