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RE: filmscanners: image samples of digital artifacts



Hi, Dan--

That looks like "Posterization" to me (at least, tha's whut ah calls it! :-) 
--cf definitions (-:|:-) ). I'd say it's probably a result (in this case, 
anyway) of pushing the sizing and JPEG compression too far. A good reference 
is Larry Berman's Compression Comparisons (BermanGraphics--You can look it 
up--I can't access the URL without losing my link on this service).

No, it's not "jaggies." Jaggies are usually those obvious "stair-steps" you 
sometimes see on contrasty diagonals in the picture, a result of not enough 
anti-aliasing or too few colors (posterization is also a result of too few 
colors). Rob G, OTOH has all sorts of dagger-shaped "jaggies" produced by 
his LS30 stepper and/or software. Here again, same term, different visual 
appearance.

Best reagards--LRA


>From: "Dan Honemann" <danh@selectsa.com>
>Reply-To: filmscanners@halftone.co.uk
>To: <filmscanners@halftone.co.uk>
>Subject: RE: filmscanners: image samples of digital artifacts
>Date: Thu, 19 Jul 2001 17:44:41 -0400
>
>Lynn, Rafe, Rob and others:
>
>One thing I've always been curious about is what causes the topographical
>map type of lines you see in the blue sky portion of this image:
>
>http://www.chebucto.ns.ca/~taiji/gallery/t21.htm
>
>???
>
>I see this sort of artifact a lot in jpegs on the web.  Is this what is
>called "jaggies?"  Do they show up in prints?
>
>Thanks,
>Dan
>


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