software - How do you optimally resize and sharpen images for printing?

What is the best way to get the clearest, sharpest print without pixelation or blurring? I have tried some sharpening techniques in Photoshop, however they are geared towards sharpening for viewing on a screen, and do not generally produce great print results. Unsharp masking does not seem to produce clearer results, as it generates more psuedo-noise, and that sometimes reduces fine details

I am an avid user of Adobe Lightroom, and I use it extensively to process my work and generate prints. I am not particularly impressed with the print quality from Lightroom. Despite using custom ICC/ICM profiles tuned to my specific printer (a Canon 9500 II) and the specific papers I use, my photos tend to lack in the area of sharpness. Lightroom also seems to have some limitations on its maximum print resolution, defaulting to 240ppi, and topping out at 480ppi. I believe my printer has a standard resolution of 300ppi, and a native resolution of 600ppi, however there does not appear to be much of a difference at either 240 or 300 ppi when printed from lightroom. I am also looking to get an Epson 3880 in the future, and I believe its native resolution is 720ppi.

I've heard of qimage, however I did not have a chance to fully explore its options and resulting quality over the 14-day trial period, and I am not sure its worth the $90 or so to buy it. (If it is worth it, I may just go with Qimage.)

Most of my prints are from 12.1mp Canon RAW files generated by my 450D, rendered through custom Hahnemuehle ICC profiles for Canon papers (fine art, museum, satin or pro photo glossy), which are really just Hahnemuehle in disguise. Color tones are great in general, perhaps lacking a bit in contrast when printed on fine art or museum paper. The images definitely seem lacking in the sharpness area...details visible in smaller on-screen versions just don't appear as striking or evident when printed, and fine edges on screen often appear softer or even blurred when printed.

Answer

Unsharp mask works just fine when sharping for print, the original method was actually used when creating prints in a darkroom. You just have to know how to adjust the parameters for the specific resolution.

A good base value for the radius is 0.1 mm, which you have to translate to a value depending in the resolution:

radius = 0.1 mm * ppi / 20

So, for images intended for screen, which has a resolution around 100 ppi, you use a value around 0.5. For an image printed at 300 ppi you use a value around 1.5.

To get an approximate preview of the effect, you can zoom the image according to the resolution. An image to be printed at 300 ppi can be viewed at 33% on the screen to see roughly what the sharpening will look like.