Digital BW, The Print

--- 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