Resizing images for whatever reason, whether it be for the web or for printing, sharpening is typically required. Depending on the lens used I will typically sharpen for the web and for print, some lens required more sharpening than other.
Additionally, when resizing images for the web it is critical to sharpen progressively as the image is downsized, this will get you a crisp image rather than a soft blurred version. Basically progressive sharpening means reducing the image dimensions whilst sharpening at different dimensions, ie sharpen image @ full size, resize to 50% then sharpen again, reduce image size to desired size and sharpen again.
As a rough guide here are some basic settings for sharpening when using Capture NX2, however they concept and qualitative values are applicable across most programs.
Typical for soft lens image, combined HDR image, image taken at slightly lower shutter speed then needed.
Unsharp Mask: Intensity 5-10, Radius 50-70, Threshold 0
Unsharp Mask: Intensity 50-75, Radius 2, Threshold 0
Image Downsizing and Progressive Sharpening
Example for resizing to a typical web size of 800x800pixels, this is a fairly light sharpening, including a another step with a larger radius like on the above example may be required for some images…
Size/Resolution to 50%
Unsharp Mask: Intensity 15, Radius 3, Threshold 0
Fit image to 800×800 pixels
Unsharp Mask: Intensity 25, Radius 3, Threshold 0