Google| Subject | Re: Lenses and sharpening |
| From | Floyd L. Davidson |
| Date | 09/13/2014 13:55 (09/13/2014 03:55) |
| Message-ID | <87k35720r3.fld@barrow.com> |
| Client | |
| Newsgroups | rec.photo.digital |
| Follows | Alfred Molon |
| Followups | Alfred Molon (8h & 28m) > Floyd L. Davidson |
Alfred Molon <alfred_molon@yahoo.com>wrote:
Alfred MolonSharpening up the focus can be done to a limited extent. UnSharp Mask is probably the most limited of various sharpening tools. Likewise any sort of "smart sharpen" that tries to isolate tonal edges will be less useful.
Sometimes a soft lens can be very effectively compensated by some unsharp mask in post processing and you get a sharp, natural looking image.
But sometimes no matter how much sharpening you apply or what parameters you choose, you get that unnatural, "sharpened" look.
It probably depends on the unsharpness of the lens, its (spatial) frequency response or whether the sharpness is caused by the lens glass itself (i.e. lens not being sharp enough), inaccurate focus or some motion blur.
For instance I have a 70-300 lens which at the tele end generates a bit soft images, which however respond well to unsharp masking in post- processing. But that's not the case for the another lens I have (a mid- range one).
Has somebody analysed this (i.e. how to best sharpen an image, what unsharpness can be eliminated in post-processing)? Is there perhaps some web page with details?
A true (not what Adobe labels as HP) high pass sharpen tool will be fairly good. The problem is that most image editors do not let the user set all the parameters, and often limit user configuration to just an amount.
One better option might be wavelet sharpen.
But probably the most useful would be Richardson-Lucy Deconvolutional sharpening. Using just standard default filters (Gaussian and perhaps exponantial) for the point spread function should work better than other sharpen tools, but it would also be possible to develop a very accurate point spread function for any given specific lens (think of the Hubble Telescope), and that would be very significantly better than other methods.
-- Floyd L. Davidson http://www.apaflo.com/ Ukpeagvik (Barrow, Alaska) floyd@apaflo.com
09/13/2014-
