Digital BW, The Print

skippy13312000 wrote:
> I'm new to digital printing and I'm curious as to the effect of the DPI 
> setting on print quality when I convert my RAW files for CS2.  I've 
> read here and there people setting 360 or 720 or whatever.  Is that the 
> optimal DPI and why?  I have a fair amount of book knowledge on the 
> subject but I'm still not quite catching the relationship between Epson 
> printers, 720/360 dpi, and print quality.
>
> I think it's because the "native" (if that's what you call it) DPI for 
> epson printers is 720 and 360 is half of that so that kinda makes sense.
>
> Thanks for any info.
>
> Brian Skipper
>   
First, we are sending the file to the driver in ppi, not dpi. We can't 
specify a dot pattern, we can only specify down to the pixel level.

The native resolution for the Epson drivers appears to be 720 ppi for 
the desktop printers and 360 ppi for the wide format printers. What this 
means is that if you give the driver some other file resolution, the 
driver will either up-size or down-size your file for you before it 
creates the dither pattern that it sends to the printer. The Epson 
driver actually does a pretty good job of this.

Note that we are talking about the Epson driver here. The printer itself 
doesn't appear to know or care so long as whatever software is talking 
to it sends it a dither pattern that it can print. A driver like the 
StudioPrint RIP seems to make use of all the information you can send it 
- it seems to create its dither pattern without up-sizing or down-sizing 
to a specific ppi setting.

As to the relationship between the file's output resolution and print 
quality, that's easy enough to see for yourself. Print one of your 
images at a handful of different output resolutions. That is, for the 
same physical dimensions of the final print, vary just the ppi. Then put 
the resulting prints side by side and judge print quality for yourself. 
For the desktop printers, I'd suggest 720ppi, 360ppi, 240ppi, and 
160ppi. The results of such a test might surprise you.
-- 
Bruce Watson
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