Digital BW, The Print

Helen Bach wrote:
> Ernst,
> 
> The tests you give the link to are subtly different from the ones I
> did because they involve sending a file to the printer at only one ppi
> value (720 ppi, according to the instructions). As such they do not
> represent true comparisons between, say, 360 ppi and 720 ppi. To
> assess 360 ppi you have to send a true 360 ppi file to the printer,
> not a 720 ppi file with pseudo-360 ppi data in it. 
> 
> By sending checkerboard and lines to the printer at different ppi
> values you can see how the driver maps pixels to the matrix produced
> by the print heads. 
> 
> Best,
> Helen

Helen,

The 1440 and 2880 dpi printer resolutions you had in your test 
message should result in 720 PPI native resolution on your 
2200. (I have no desire to load the printer driver and check 
that with Qimage's preview window). If so the 360 PPI file you 
send to the printer gets a 360>720 upscaling in the driver. 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).

That doesn't say you will see 720 PPI or even 360 PPI quality 
on the paper. It could be an odd number ranging from say 187 
to 411 PPI if the test shows such in between steps. It doesn't 
tell you the native resolution but the actual print resolution 
for the combination of printer driver settings and the paper 
used. Yet we have to use the 720 PPI native resolution to get 
there. Gloss papers give better results, matte less. 
Theoretically, extrapolation software without any flaws would 
allow you to use actual print quality PPI as input and the 
rest could be hidden from the user and result in best quality 
possible. But who does all the quality checks on all the 
papers + settings to feed the printer the most economic PPI 
file for each job ? Better use an application then that makes 
the best of the file you already have. Too much data is often 
more a problem in spooling etc than not enough, the last often 
shows more quality than expected.

Ernst
                    --
           Ernst Dinkla


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