Rafe, thanks for your excellent response. I'm not exactly a newbie at
scanning and Photoshop, but I obviously still have a lot to learn. Thanks
for providing the definitions of "resize" and "resample." In the past, when
I would resize in Photoshop, I always left the "Resample" box checked. I
would first memorize how many pixels the image had, then I would enter the
document size I wanted for my print, then I would change the resolution until
I ended up with exactly the original number of pixels. In other words, I was
resizing to get the print size I needed, but I was using some extra effort to
keep the pixel count the same because I didn't want to resample and destroy
any image information. But now, I know that all I have to do is uncheck the
"Resample" box and Photoshop won't let the pixel count change. Then I can
enter what ever print size I want and Photoshop automatically changes the
resolution to keep the pixel count constant. Absolutely amazing! And what a
time saver for me.
Also, good information on using 1600 ppi for the 1640 scanner, rather than
3200 ppi. I have a Microtek ScanMaster 5 flatbed that also has asymmetrical
resolution. I should run some tests to see if it makes any difference with
my scanner if I use the lower resolution value when scanning.
In a message dated 7/8/2001 4:09:45 AM Pacific Daylight Time,
rafeb@channel1.com writes:
Roger, there were a couple of points in your recent
post to Rick Decker that I'd like to comment on.
My experience with the 1640 SU is that there is
absolutely no advantage to setting 3200 dpi
resolution (as compared to 1600.) There are a
number of scanners out there with "assymetrical"
resolutions, and it's usually a shell game.
Ditto for printer resolutions. The number
that matters is the lower one. The higher
number is simply for ad copy. "Looks good on
the side of the box" -- as the marketing guys
say.
The other is the matter of resizing/resampling
the image in Photoshop. You (and Rick) should
understand the difference.
In Photoshop's Image->Image Size dialog, there's
a check-box labeled "Resample Image."
If you CHECK this box, PS will either "create" or
throw away pixels according to the resolution,
height, and width that you ask for, and the
resolution, height and width of the existing
image.
If you UN-CHECK this box, PS will neither create
nor destroy pixels; it merely changes and internal
tag, somewhere in the image file, that determines
the physical size of the printed image.
If you scanned a 35 mm frame on the 1640SU, you
get a file that's 1600 x 2400 pixels (let's use
round numbers here.) If you set target size at
100% in the scanner driver (I'm working from
memory here) it will arrive in Photoshop sized
at 1" x 1.5". If you print it that way, you'll
get a 1" x 1.5" print.
So you want to resize or resample. Which to
choose? Fortunately in Photoshop, it doesn't
matter much -- Photoshop does a good job
resampling. But just bear in mind -- with
"Resampling" an entirely new image is created,
pixel by pixel. With "Resize" the original
pixels in the image remain untouched. (So
"Resize" happens almost instantaneously,
whereas "Resample" takes some time, maybe
15-30 seconds on this image, on a reasonably
fast machine.)
A "Resize" of this 1600 x 2400 image might
yield, for example:
-- an image 2" x 3" at 800 dpi
-- an image 4" x 6" at 400 dpi
-- an image 8" x 12" at 200 dpi
and so on.
"Resize" is probably more of a purist's
approach. There's no possibility of degrading
the image in any way.
"Resample" will either create new pixels (by
interpolation) or throw them away (by averaging
and decimation.) With "Resample" an entirely
new image is created for you.
Finally... bear in mind that the scanner's
rated dpi has almost nothing to do with sharpness.
I can prove to you easily that the 1640's
so-called "1600 dpi" yields an image much less
sharp than a Polaroid SprintScan Plus working
at 1350 dpi -- half its rated resolution.
