Blur Width

In order to focus an image, Focus Magic needs to know the amount by which the image is out of focus.  This is specified by the “Blur Width” and is the distance that an edge has spread (in pixels).  When you open an image, Focus Magic auto-detects the Blur Width, but it is advisable to experiment a little.

Examples of Different Blur Widths for an Edge

Blur widths of an edge in an image

The “Blur Width” can also be thought of the diameter of the circle to which a single pixel spreads when the image goes out of focus.  Knowing this, a fairly accurate way to determine the blur width of an image is to look for point sources and measure their diameter.

"Focus Magic is a remarkable piece of software. It's an honest-to-God real sharpening algorithm that works as a stand-alone program or a Photoshop plug-in. I'll spare you the math about how it works. What's important is that this is not a mere edge-enhancement routine like most so-called sharpening filters; this one actually undoes the blur."
Ctein (Photographer & Author)
Photographer, artist, author