Digital BW, The Print

For the 2200.
In 1440 mode, there are 720x1440 dots, and three sizes of dots are
available.
In 2880 mode, there are 1440x2880 dots, and only the smallest dot size
available.
I believe OPM uses 1440; it does for the R200.

The dots the printer puts out are “screened” from the image data.  Google
halftone and stochastic screening for info.

The link Ernst provided was for print evaluation of photographic images;
more appropriate than checkerboards, give it a try.

Best regards,
John Moody

-----Original Message-----
From: DigitalBlackandWhiteThePrint@yahoogroups.com
[mailto:DigitalBlackandWhiteThePrint@yahoogroups.com]On Behalf Of Helen Bach
Sent: Tuesday, March 14, 2006 1:41 PM
To: DigitalBlackandWhiteThePrint@yahoogroups.com
Subject: Re: [Digital BW] File Resolution

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Ernst Dinkla
<E.Dinkla@...> wrote:

> I think it is better to start with 720 PPI right away then,
> instead of creating a pseudo 720 PPI test image with 2x lines
> and squares if the extrapolation does nearest neighbour (not
> bad in this case).

Ernst,

I must have explained it badly, because that is exactly my point.
The resolution tests you gave a link to did not print a true 360 ppi
file. They printed a 720 ppi file with psuedo-360 ppi images in it -
which is not a true representation of a 360 ppi file.

My tests were with files at true ppi values, no resampling, no
interpolation. I'm testing the match between the file and the printed
image. The best match between the file and the image occurred when a
288 ppi file was sent to the Epson driver and at 360 ppi with OPM.
That's not necessarily the best file resolution to use, it's just a
test for me to try to understand what the two drivers are doing.

If 720 ppi is the native resolution of a 2200, as Epson say, how many
dots are there per pixel? How many dot sizes? How many possible
colours? Why does a 720 ppi file get altered - ie why isn't one file
pixel mapped exactly to one printer pixel? These are the questions I'm
asking myself, not rhetorical questions.

Best,
Helen




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