...but image restoration. There is no reason to use it for images that do not suffer from blur of some kind. However, for blur (shake, OOF, diffraction, lens flaws) removal it is the tool to use.
For an image that already has pretty good overall sharpness, deconvolution can be a useful form of sharpening (keeping in mind that sharpening is, essentially, edge contrast enhancement).
Deconvolution is not sharpening in the same sense unsharp mask is; it is
not edge contrast enhancement. Instead a deconvolution kernel is applied to the image to remove the blur. If the point spread function is well known, even major blur can be restored - indeed it image restoration rather than sharpening. In typical photography the PSF can only be estimated to reasonable degree, limiting the image restoration to degree. Astrophotographers have the advantage of having point light sources to help in the hunt of the proper PSF (which itself is not the same across the image as the lens in use also modifies the function).
It isn't free of artifacts, however, and must be applied conservatively.
With a very good PSF estimation one can apply loads of deconvolution and the results will be amazing. However, if the PSF is somewhat off, the results won't be great, so it's better to be safe than sorry. Wit a decent PSF and proper use there won't be artifacts to quack of.
For example, it tends to introduce artifacts into out of focus areas of your image (it can take nice bokeh and render it not-as-nice with ease).
Only if your PSF is really off, but then your sharp areas won't look as they should either. Also, if one really needs to restore a blurred image, one is also likely to use deconvolution selectively on parts of the image.
And sharpening Foveon images introduces its own little kinks into the worfklow as you cannot approach it the same way as you do images derived from Bayer interpolated images.
This is false as long as we're not operating on the actual raw-files or capture sharpening.
There are a couple of differences with Foveon and
most color filter array equipped cameras. Most importantly the antialias filter. Cameras with it do need capture sharpening, those without don't need it, and should not be given any. For
output sharpening there is no difference between Foveon, Bayer, scans etc. (other than handling of noise).
I recomment anyone interested in deconvolution to try out (free/donationware)
Image Analyzer (
http://meesoft.logicnet.dk/ ). It's not perfect, but instead quite easy to get into this. For heavy use there is ImageJ and a couple of plugins one may want to look into, but they're a bit more complex to use (but much more powerful).
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Quack!
