I have been learning how to use Nikon's ViewNX, the free software that comes with their digital SLRs. My interest is mainly in working with NEF (Nikon Electronic image Format) "raw" files. I am also getting ready for a beginners' class in digital photography and digital darkroom that I will teach this Summer.
The "Quick Adjustment" tools include Sharpening, with a range of 0-10. I must assume for the present that this is similar to the 0%-100% range seen in other software (I am most familiar with Irfanview; by the way, with its plugin package, Irfanview can handle NEF files).
For the sake of my students, I created this montage. Click on it for the 900x600 original. Printed on a 6x4 inch sheet, it shows the effect of the sharpening levels noted at 300 dpi and 150 dpi, as printed. The clips are from an image of a dogwood tree, taken in full sun, ISO 200, f/8, 1/320 sec.The unsharpened image shows the raw resolution of the lens and sensor combination. The D40's sensor has a pitch of 8µ, and the circle of confusion for f/8 at 600nm is 4.8µ. Thus the slight "fuzziness" of the Sharp0 clips primarily shows lens performance. Not quite diffraction-limited, but within a factor of two. The "Sharp2" images have the look of being diffraction-limited, while the Sharp4 and Sharp8 images look over-sharpened. At Sharp8 the sky is getting a granular look also. I like the look of Sharp2 the best, at both resolutions.
I know what is really happening. A 100% sharpened image is created and proportionally added to the unsharpened image, but the images with just a little sharpening added look as good as images would with a specific algorithm (using Fourier transform) to deconvolve the fuzziness of the unprocessed image.
A Tip: When using ViewNX, if your PC is a few years old, as mine is, have a book with you. Each sharpening operation took more than half a minute on a 6Mpx image, saving intermediate results took about an equal amount of time, and converting to a 'jpg' file took almost a minute.
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