Digital BW, The Print

Austin,

Here is a reply from Kennedy McEwan on the x7x list on the same subject. He
seems to believe (has proved?) that the Epson driver upsamples to 720 or 360
ppi depending on the model.


"Well, if you look through the archives of this list you should find a
posting made over a year ago by either Royce or Chris Bair which
referenced a test pattern which clearly demonstrated the limitations of
the Epson driver's resampling algorithm when printing at other than the
optimum resolutions.  First resamplng to 360ppi (for large format
printers) or 720ppi (for desktops) using bicubic interpolation certainly
made a very visible improvement on that image.

In addition, one of the first prints I ever made on my Epson was a
synthesised resolution test pattern and this certainly produced very
visible artefacts due to the Epson resampling - in fact, that is how it
was possible to determine what fundamental resolution of the Epson
driver was.  A 1440ppi line resolution test image can quite literally
change from black to white simply by moving the lines one pixel left or
right, whilst sub-optimal resolution tests close to 720ppi produce broad
aliasing bands - all of which would be significantly reduced if not
eliminated by the use of adequate quality resampling methods.

So there are certainly cases where the difference between leaving it to
the printer and using a higher quality resampling algorithm do make a
very visible difference to the output but, as I mentioned in another
thread, this is usually only true of synthetic images, for reasons
already explained in that posting.

I also prefer to let the printer sort it out, although within slightly
different bounds, when using real images from cameras or scanners, but
always resample digital art to 720ppi with bicubic interpolation or
resize the entire artwork to yield a suitable resolution.

Also, if you check the "DCC" or "Digital Camera Correction" box on the
driver you will find that the driver produces much less "stair stepping"
on low resolution images.  With that mode, it uses bilinear resampling
rather than nearest neighbour to get up to the fundamental resolution of
the printer."


----- Original Message -----
From: "Austin Franklin" <darkroom@...>
>
> It COULD work that way...but there is no reason it has to.
>
> > Let's say the code routine in the driver which perfroms the pixels->dots
> > conversion has been written so that it can only accept an input
resolution
> > of 360ppi. There will be a routine in the driver which would then first
> > check to see whether the image resolution passed to it by the imaging
> > application/print spooler is at the correct resolution to be passed to
the
> > pixels->dots function, and if not, it will do this resampling.
>
> Understood, but again, that's an assumption that it works that way.
>
> > Note there
> > are two separate things happening here in the print driver:
>
> In this hypothetical print driver, yes.