RE: [Leica] Scanning slides

["Clive Moss" <chmphoto@sbcglobal.net>]

"Real World Photoshop" by Blatner and Fraser recommends sharpening both
after scanning, if needed, and before printing.  
One day I will burn through enough time, paper, and ink to figure out the
answer myself -- but for now I will listen to the expert opinions -- if I
could only figure out which to listen to :-)
- -- 
Clive
http://clive.moss.net

> -----Original Message-----
> From: owner-leica-users@mejac.palo-alto.ca.us 
> [mailto:owner-leica-users@mejac.palo-alto.ca.us] On Behalf Of 
> Michael Chmilar
> Sent: Thursday, July 17, 2003 11:49 AM
> To: leica-users@mejac.palo-alto.ca.us
> Subject: RE: [Leica] Scanning slides
> 
> 
> Clive Moss <chmphoto@sbcglobal.net> said:
> 
> > Hmmm -- that is not what I thought. When I do print, I have 
> been resizing
> > and resampling, then sharpening at the resampled 
> resolution, viewing the
> > image on the screen at 1-1 pixel resolution.
> > 
> > What should one do about sharpening if one does not resample? 
> 
> 
> First, what is sharpening:
> 
> The sharpening algorithm works by increasing the contrast at the
> borders between contrasting image regions. For example, if you
> have a region of light gray and a region of dark gray, with a
> sharp border between them, the sharpener will change some light
> gray pixels towards white, and some dark gray pixels towards black,
> right along the border. This makes the border "stand out" more
> strongly to our visual system.
> 
> I have read/heard about two schools of thought about sharpening:
> 
> 1)  Sharpen after scanning.
> 
> This would be done to counter any deficiencies in the scanner,
> that could "soften" the image. However, with any reasonable
> modern scanner, this probably isn't necessary.
> 
> Some people may still sharpen after scanning because they think
> that the image looks better onscreen.
> 
> Personally, I would not recommend sharpening after scanning.
> If you think about the sharpening algorithm as described above,
> all you are doing by sharpening at this step is just mucking
> up your data.
> 
> 2)  Sharpen before printing.
> 
> This will create the perception of extra sharpness in the print.
> 
> The sharpening should be done after the image has been resampled
> for the printer. If you are going to print two different sizes,
> say 8x10 and 16x20, you will sharpen separately for each print
> size.
> 
> This is because the sharpening effect depends on both the
> _amount_ the local contrast is increased, and the _area_ it
> affects.
> 
> If you are going to rely on your printer's driver to resample
> the image, then you will have to use trial-and-error to find
> the right sharpening settings. On-screen inspection on your
> computer's monitor will not be very useful.
> 
> You must be careful when using sharpening. If you apply it too
> zealously, you can introduce unwanted artifacts in your image,
> like "ringing" effects along edges. You can also end up sharpening
> the film grain, which you probably don't want to do.
> 
> I have seen some grossly oversharpened images that look super
> sharp at first glance, but look truly awful on closer inspection.
> 
> btw: If you want to learn more about this kind of stuff, I
> highly recommended taking the course "Digital Printing for the
> Fine Art Photographer" offered through http://www.calypsoinc.com
> It is worth the price of admission just to learn about sharpening!
> 
> later,
> Mike

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