I've done enough sharpening for web to have a decent grasp of it but haven't printed alot of those pictures and what I have printed have been small (no bigger than 5x7). I'm wanting to print bigger (16x20) but don't want to waste a ton of paper practicing too much.
So, what are the differences between sharpening for web and sharpening for print?
There are probably those who can give you a more technical answer but I have found a simple solution for me. After resizing the file for the larger print size I then view it at 50% size and sharpen until it looks just oversharp. The large prints then seem to come out just about right.
Basically you need to sharpen at 1 point per 100 dpi, at 100%.
So if you going to print at 300 dpi then your unsharp mask needs to be 100% at 3 points, for the web (72 dpi) your unsharp mask needs to be at 1 point or less for 100%
I have found that unsharp mask works great for web based images, but I use the high pass filter on a duplicate layer, set to overlay for print sharpening. Try adjusting the amount in the high pass filter between 2 and 5, depending on the size of the image. You can then vary the opacity of the layer to vary the effect.
If you don't want to waste paper, you can try sharpening the whole print, then select an area of detail and crop, so that your are only printing a 2" x 2" or 3" x 3" sample. This saves paper and ink, but you are not down sizing, just printing a small sample of the large image to check the details as printed.
You might pick one or two test images, sharpen each at several varying amounts, and place 100% cropped selections all on one print so you can compare and save paper. See what settings work for you and your images and your printer ...
When using Unsharp Mask, I often apply "lighter" settings twice instead of a more substantial setting once -- I find it sometimes helps prevent halos from forming.
