The Long-Promised Depth of Field tutorial (Part 1 of ?)

OK, so for months and months now, I’ve kept threatening to do a tutorial on how to use Depth of Field.  People like the way I use it, apparently: I have to admit I’ve pulled off some stuff with it that I really can’t believe I did without using Photoshop.  All the pics in this tutorial were done using in-viewer post-processing.  I didn’t do anything outside of my viewer except for cropping them.

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First off, what IS depth of field?  I grabbed this pic as a good example for talking about what it is, and how it works. Continue reading