On 10/26/2010 4:14 PM, Chuck Norcutt wrote:
> ... As far as I'm concerned the image is dimensionless until it comes time
> to print.
Yup, in a sense. In another sense, it has dimensions in pixels, but not in
physical dimensions.
> Then the image is cropped if necessary and resized to produce a 250 or 300
> dpi output print.
Here, I think you may be mishearing Bob. He's saying that there is no reason to
resize at all if the native pixel
dimensions of the image and the chosen physical output dimensions result in a
ppi between 180 and 400+. Although almost
certainly empirically based, I can see where this could come from.
No matter how it starts, your image has to go through a great deal of
processing before flying print heads squirt teeny
droplets of ink onto the paper. (Yes Veronica, inquiring folks have pretty
convincingly demonstrated that ideas of
"native resolution" have no discernible effect on output quality.)
When you send it to the printer, it goes through at least three steps of
processing. The first two occur in the printer
driver or RIP*.
The first is conversion to colors the printer understands, as generally with
inkjets, RGB to CYMK, and adjustment to the
particular printer, ink and paper characteristics to as accurately as possible
match the image colors. This may involve
use of proprietary data the maker has put in their printer driver or ICC
profile matching.
The second is conversion of the image data into a string of commands in the
printer's own language.
The third occurs as the printer's firmware interprets the commands into a
series of electrical signals to the physical
print mechanism.
Now that's a lot of processing, that ends up not with an even pattern of dots
of single colors, but in a pattern of dots
of various colors. Four color is long gone in photo printers. The one sitting
here has eight cartridges, although two
are blacks and one isn't a color at all, but a surface. So CYMK now is
translated again, to CcYMmK, or CYMKkRB, or
whatever inks that particular printer uses
What it produces on paper isn't like screen printing, where color dots in a
fixed pitch vary in size in an analog way.
Although we think so, do we even know if the droplets are put down in a fixed
pitch? The printer makers sure aren't
telling the details of how they hope to do better than their competitors. Are
the drops all one size?
According to their specs, these printers are laying down dots at a much finer
pitch than the pixel pitch sent to them.
So they are, in effect producing a rather subtle matrix or mist of colored dots
that, together with the color of the
paper, add up to the image.
I go into this detail to suggest that, within a fairly broad range,the dpi of
the input may have little effect on the
process of printing it.
Some of these RIPs/drivers are very clever. QImage, for example, is a print
manager that includes it's own RIP. A few
years ago, a friend needed slides of some people/things he didn't have pics of.
He searched the web, only to come up
with some very low res images. I tried all sorts of things to upres/enhance
them. Nothing in PS, either its own or a
couple of plug-ins, really did much to improve the prints.
I tried QImage. Just amazing. I don't know what it did, but images printed with
it and its sizing and sharpening
functions were at least an order of magnitude better. They almost made me
believe in those TV shows where eight pixels
are "enhanced" so you can read the license plate.
Am I going to mess around resizing my images to some old standard idea? Nope,
they are going into QI at whatever
camera/scanner native pixels I have and I'll tell QI what size prints to make.
Clearly, it does its processing with
prior knowledge of how the printer will render what it puts out. That's way
smarter than me deciding what ppi to resize
my image to.
Print Me Moose
* Raster Image Processor. RIP is to printer driver roughly as Giclée is to
inkjet. They do the same thing, but one has
more pretentions, costs more and may be better than the other.
> It gets sharpened after the resizing.
Again, I do resharpening for web images, but not for printing with QI.
> I don't see any reason to go to 400 dpi.
As above, try not resizing at all between 180 (maybe even 150) and something
over 400 ppi. let the smart soft/firmware
do it's job.
> There aren't many Mooses around. :-)
Pick one:
How blessed are they who know one. :-P
Thanks for small favors.
But keep your choice to yourself, There will be a test later. :-)
Moose
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