One of the things that seem to confuse people about
document scanning is dpi. This is an abbreviation for dots per inch.So it is how many measurements the scanner will make for every inch of the document. So the greater the dpi the finer grained the resulting digital image.
For black and white images it will either be measured as black or white so it is one bit per dot. For color images there are 48 bits per dot. So the size of the resulting digital image is a function of how many dpi and if it is color or black and white.
Now you know what dpi you might think that higher is better. But this is not always the case. So what is a good dpi for your document scanning project? The most common for standard office documents is 200dpi. That is sharp enough to be used read or re-printed. It is also good enough for OCR software. Consider for a second that back when we used to fax documents we were using 75dpi and they are readable and used as legal documents.
There are people who are convinced that 300dpi (or even greater) is a requirement. There is no doubt that it will achieve a "smoother" looking document. But the same result with software that every scanning service uses. Higher resolution scanning can also pick up dots in the original. This can be distracting and then the digital images need to be "cleaned" with the same software package that could have smoothed out the 200dpi scan.
The other thing to consider is the size of the digital image. A 300dpi is not 33% larger than a 200dpi one, it is over 500% larger. With a reasonable sized project that can result is significant increases in digital storage and backup required.
Perhaps the most important thing to consider is cost. It takes three times longer to scan at 300dpi than 200dpi. This either will cost you time to run them all through or increase the cost of the job if you have it outsourced.
So before you let someone talk you into a higher resolution consider why you really need it. We can scan at any dpi you specify but the cost to do the work and the cost to store the electronic records will change accordingly.
Labels: document scanning, dpi