Alin Flaider wrote:
>
[snip, snip]
> The 2400 dpi resolution is achieved via two 1200 dpi, half shifted
> sensor rows, that HP calls staggered pixel sensor and claims it
> delivers lower noise levels than a true 2400 dpi single row. There's a
> third 600 dpi sensor row for fast, sub-1200 dpi paper scans.
> I scanned both negatives and slides at maximum resolution, and I
> must say that the HP's compromise shows up. It's clearly better than
> 1200 dpi, but definitely not a true 2400dpi scan.
That's really to be expected. Two staggered 1200dpi sensors result
in a pixel pattern rather like this:
* . * . * . * . * . * . *
. * . * . * . * . * . * .
(where the '*'s are the pixel centres, and the '.'s are just grid marks)
repeat this pattern a few times, and you end up with the following:
* . * . * . * . * . * . *
. * . * . * . * . * . * .
* . * . * . * . * . * . *
. * . * . * . * . * . * .
* . * . * . * . * . * . *
. * . * . * . * . * . * .
* . * . * . * . * . * . *
This looks astonishingly like a regular pixel grid rotated 45 degrees.
The true pixel spacing isn't 2400dpi - its 2400/sqrt(2), or 1700dpi.
The intermediate '.' pixels are generated solely by interpolation.
Fuji, incidentally, use exactly the same bogus pixel counting method
in their '6 megapixel' consumer digital camera; they rotate a 3.1 MP
array by 45 degrees, and double the pixel count by interpolation (in
addition to the chroma interpolation common to most digital cameras).
--
John Francis [EMAIL PROTECTED] Silicon Graphics, Inc.
(650)933-8295 2011 N. Shoreline Blvd. MS 43U-991
(650)932-0828 (Fax) Mountain View, CA 94043-1389
Hello. My name is Darth Vader. I am your father. Prepare to die.
-
This message is from the Pentax-Discuss Mail List. To unsubscribe,
go to http://www.pdml.net and follow the directions. Don't forget to
visit the Pentax Users' Gallery at http://pug.komkon.org .
