Understand DPI, it affects many things in Scan Tailor

[Misty]

It does vary a bit over the course of scanning a book, because the first page in a book is going to be a little closer to the camera and will take up more of the frame. I haven't typically found that it causes much difference to Scan Tailor, however. The only time I've had a very significant change was when the book was within less than a foot of the camera while scanning militia handbooks; in that case, I did have variations of up to 70DPI or so over the course of the book, but that didn't cause undesired results in Scan Tailor either.

[univurshul]

For Mac users as myself, finding the correct DPI works as follows.
I use the shareware GraphicConverter from http://www.lemkesoft.de/. It has some rudimentary processing possibilities...This is very exact, but in my experience, it could vary a bit...

I just tried this and am liking it; precise numbers, accuracy and makes sense. Thanks TJ-Shredder!