Archived posting to the Leica Users Group, 2002/07/14
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At 10:52 AM -0700 7/14/02, Darrell Jennings wrote:
>Sounds like I am operating the same way you are Paul.
>
>However, if you don't see improvement after 360DPI,
>aren't you better off to down res to that size and
>save the disk space?
>
>Have you run any tests on just scanning at 360DPI to
>begin with vs. at full res and then downsizing the
>DPI?
>--- Paul Chefurka <paul@chefurka.com> wrote:
>> On Sun, 14 Jul 2002 19:19:18 +0200, "Steve Unsworth"
>> <mail@steveunsworth.co.uk> wrote:
>>
>> >Don
>> >
>> >I always print files at 360 DPI (a multiple of the
>> 1440 DPI my printer
>> >is capable of) I've always sort of assumed that
>> having the one directly
>> >divisible by the other makes things easier for the
> > printer driver (I'm
<snip>
There is a big difference in scanning at 360dpi and outputting to a
printer at 360dpi, and a printer having a nominal 2880 resolution.
Usually, it's best to scan at the highest resolution the scanner can
handle; at least with colour and chromogenic B&W film. That way you
get the most info out of the film. This may be 4000dpi or whatever.
It relates to the dimensions of the film, so if you have 35mm film,
which usually has images of 24mm in the short direction, you get just
under 4000 pixels of information in the short direction. If things
are all aligned properly, and the MTF of the system is 1.0, you get
4000 pixels of useful information with a bit depth of 24 or more
each. If you then want to make an 8x10 print, you have to resize the
image, which gets you 4000/8 or 500dpi at the very best that you can
output to the printer. If you now send 720dpi or anything above
500dpi to the printer pads the file with no useful information. It
slows things down, but doesn't send more real information.
As others have noted, 360dpi is a reasonable maximum to send to a
1440 or 2880dpi printer. These 1440 or 2880 numbers refer to the
maximum theoretical resolution of the printer, which has to make up a
given tone on the paper by combining various amounts, spacings and
number of dots of the various inks to represent one of the 360dpi
that the computer sends it. The printer has a resolution of 1440 or
2880dpi so that the tones will appear smooth, and you won't see the
individual squirts of ink. 360dpi is close to the maximum that paper
prints can resolve, in any case.
So.... the best thing usually is to import your hi-res scan, do your
Photoshop layers, curves, etc, resize to 8x10 at 360dpi and then do
your sharpening. Then send that to the printer. It's efficient, sends
the maximum amount of useful info to the printer and will give you
the best quality.
You'll note that if you have 4000dpi of info in the short dimension,
and you want to make an 11x17 print, you'll have 4000/11 or 363dpi
worth of info at best. That's why 4000dpi scanners are deemed
excellent for up to 11x17 prints. The nice thing is that if you are
making larger prints, whether wet or digital, as they get larger you
expect your audience to step back a bit, and the print will still
look good even if for a 24x36 print you only have 166dpi worth of
real info to send to the printer.
- --
* Henning J. Wulff
/|\ Wulff Photography & Design
/###\ mailto:henningw@archiphoto.com
|[ ]| http://www.archiphoto.com
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