Digital BW, The Print

outdoornm schreef:
> 
> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, "hflockwood"
> <hflockwood@...> wrote:
>> 
> Harry,
> 
> You are not reading what Michael has said.   He said that a higher
> resolution scan created a file that showed more grain and was softer.
> We all know the mantra to scan at high res for possible future use,
> but possibly higher res scans magnify grain.  Has this issue been
> covered?
> 
> Lincoln

Make it "aliased" grain.

Compare what a scanner with a true higher optical  resolution resolves
and one with a lower resolution. Both will make aliased grain but not
the same.

Reduce the aliased grain in both a lower resolution and higher
resolution scan from the same scanner and compare the scans on detail.
If there is no extra detail the scanner just doesn't resolve more than
what the lower resolution already did.

The Epson 4870 has resolution settings that go way above the actual
optical resolution it has. So higher resolutions will not create more
detail yet the grain particle will be made with more pixels than a lower
resolution scan that gives the same detail, the same result you would
get with upsampling. At pixel view the grain will be bigger, the image
softer.

The Epson hardware already oversamples by nature. Not a bad thing as it
can create a bit more dynamic range that way due to lower noise as a
result of oversampling. The scan can use a lot of sharpening so some
softness isn't an issue. Either use multi sampling in the driver or the
highest resolution, it will bring similar results.

True optical resolution of that scanner is  1500 -2000 PPI depending on
the scan method. But you will need a higher resolution (actually
sampling rate) set in the driver to get that true optical resolution or
use an odd number say 2351 PPI to force the driver to the highest
sampling rate and let the driver do the downsampling. As the last will
not have the best anti-aliasing on downsampling I would prefer to use
the highest sampling rate and the downsampling done by one of the better
downsampling programs.

http://www.xs4all.nl/~bvdwolf/main/foto/down_sample/example1.htm

Your image doesn't have to have repeating detail to make a good
anti-aliasing filter necessary, grain or more correct aliased grain in
the scan behaves the same in downsampling.

Or use a noise reducer like Neat Image and do the downsampling after
that to a resolution that holds the detail but removes the void pixels.

So in one case we think we see larger (aliased) grain but it is just
more pixels per grain particle, in the other case we get larger aliased
grain because aliased grain is even more aliased in downsampling.

Check Time Vitale's PDF on aliased grain:
http://cool.conservation-us.org/coolaic/sg/emg/library/pdf/vitale/2007-04-vitale-filmgrain_resolution.pdf

http://www.boeringa.demon.nl/menu_technic_ektar100_grainstructure.htm

What might be an interesting route to smaller aliased grain sizes is the 
use of ultraviolet light source in a B&W film scanner. I think the blue 
filtered sensor will still be sensitive enough down to 350Nm. The lens 
will cope as well and other glass in the optical path has to be tested. 
Whether an Epson 4870 will be the right Guinea pig is another matter.

-- 
Met vriendelijke groeten,   Ernst

Try: http://tech.groups.yahoo.com/group/Wide_Inkjet_Printers/

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