Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Paul" <roark.paul@...> wrote:
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> "dlruckus" <dlruckus@> wrote:
> >
> > 
> > ... film scans in the "olden days" ...
> 
> (I still have my favorite MF film cameras and a freezer with lots of MF Tech Pan in it, not to mention 25 years of MF negs [not in the freezer].  I do understand those who stay with or go back to film.  There is some magic in a B&W neg that is just not there in a digital file. But then the digital file has its own magic also.)
> 
> 
> > it comes to mind that the image sizing and mathematics methods might even have some application to improving slightly out of focus areas in any image.
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> I've read of some people doing work to "decode" out of focus areas.  The math they are using is well beyond my rudimentary undergrad math.
> 
> 
> > It might even be better used with color to black and white conversions.  Even today with digital captures it seems that a major problem has been color fringing which, to me, is very similar in effect to other focus issues.
> 
> Very interesting observation.  At least some of the fringing may be due to the fact that lenses are just slightly different focal lengths for the different colors.
> 
> My conversion process almost always uses a "split channels" step.  This results in 3 B&W images, each filtered with either a red, green or blue filter. With very good lenses, these should be perfectly aligned already, but with a lens that fringes badly, they won't be.  
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> I have not tried this, but these could be made into layers and then the "Edit > Auto-Align Layers" routine used.  This just might eliminate the fringing.  I suspect the layers could then also be re-assembled for color work as well as simply making sharper B&W images.
> 
> Paul
> www.PaulRoark.com
>
Most if not all of the panoramic (stitching) creation software can correct for lateral chromatic aberration. 

Hugin is an open source option and there are two others that I know of and have used PTAssembler, there is also PTGui and for anyone on a Mac there is PTMac.

These all use to some degree the library of math functions created originally by Professor Helmut Dersch, a German physics professor, who kindly donated his work to the world.

These above software, or some branches from the panorama software also has options for focus stacking and exposure stacking (yes HDR is the term ommonly used) but there are good and bad uses of that technique.

Anyway just thought I'd mention that for anyone interested in investigating the possibilities

BTW the sharpening of out of focus (reconstruction of image data) is called deconvolution.

I saw an example years ago when a paedophile was caught fro a photo that he'd run a swirl filter on his face to hide his identity and a technician had unswirled the result to recreate the photo

Glenn