Re: Print Quality

Sandy,

Below is an Epson Tech PDF on maximum print length for Epson Wide Format and
Desktop printers.

http://files.support.epson.com/pdf/pro76u/pro76ups.pdf

Interestingly it states that current desktop models rasterize the file at 720
ppi and Large Format Models rasterize the file at 360 ppi. What this
implies is that for desktop printers, files get interpolated UP to 720 or DOWN to
720 when sent to the printer. For the large format printers it's the same
deal, only the file is interpolated to 360 instead of 720.

Remember, it takes a few printer dots to render the tone and color of a
pixel.

Artifacts usually seem to rear their ugly heads in some images when the
resolution of the file sent to the printer is not a multiple of the above—240, 360,
480, 720

All this being said, don't expect fine detail in an image at 720 ppi to get
rendered clearly when sent to a printer (with printer resolution set at 2880).
 For one thing, dot gain takes over and so does the dither pattern. Fine
detail seems to start to go south around 480 ppi. You can also get puddling
with some surfaces.

Most of these issues are loupey—you have to look at the print with a loupe to
see what is going on. To the bare naked eye, you may not see any
difference. I have 5 different Epson printers here that I have tested for digital
negatives and I doubt that most people could see any difference in their printing
from a distance of two feet—well, maybe 2' 3.5"

High *Printer* resolutions (dpi) are really not so great with matte papers.
They print better with 1440 or 720 dpi, though there are a few papers with
coatings that can hold the dot gain with the higher printer resolutions. The
matte papers also give better color at these lower printer resolutions because
the inks don't mix and get muddy.

The newer printers like the Epson R800 boast 5760 x 1440. The higher
number, in this case 5760, is in the vertical direction. This is a function of the
paper advance. So, it's not a 5760 dpi x 5760 dpi printer. The lower
resolution is the "true" resolution—1440. However, this printer has a very small
variable dot size capability, 1.5 picoliters. The advantage of that 5760
figure, is that the printer can advance the paper in very fine increments and
overlap the ink spray coming from the print head. This gives a smoother pattern
of the ink, finer detail, less banding—so there is an advantage. Sort of
like going over a piece of furniture with a paint sprayer a number of passes
instead of trying to do it in one pass—smoother coat and less running.

Other brands of printers have their own optimum resolutions, but I don't have
any of those.

I don't know why these companies aren't more forthcoming with what optimum
file resolutions should be sent to their output devices. Obviously some of it
is partly hype. Sometimes the people you talk to don't even know—including
service bureaus and sales personell. This morning I had breakfast with
representatives of a company that sell a very high end ($250,000+) digital imaging
device. They couldn't tell me the optimum file size to send to the damn
thing. Finally the inventor of the device joined us and he could answer the
question. This information should be stamped on the side of the damn machine for
that much money.

In the end, you have to find ways to test your printer wth different targets
and see what settings work the best for different media. Be sure to run a
print head allignment on the media you are testing, or you won't get valid
results.

Hope that helps

Mark Nelson
Precision Digital Negatives

In a message dated 4/17/04 11:15:20 PM, sanking@clemson.edu writes:

> Don,
>
> Thanks for your comments.
>
> Yes, I meant 5760 X 2440.
>
> I am primarily trying to understand what the higher (5760 dpi) figure
> means. In other words, all other thing being equal, what would be the
> advantage of a printer that advertises resolution of 5760 X 1440 over
> one that is rated at 2240 X 1440?  Since this is a printer and not
> scanner I assumed that interpolation was not an issue?
>
> BTW, my Epson 2000P is only 1440 X 720 dpi, and yet it is capable of
> making very sharp prints and negatives.
>
> Sandy
>
>
>
>
>
> >Sandy,
> >
> >I assume that the 5760 (2 x 2880) is an interpolated dpi value and not a
> >native printer value. Also do you mean 2880 instead of 2440? The native
> >printer values for print dpi are usually multiples of 360 - 720.
> >
> >But to answer your question the difference in print quality depends on the
> >image and the substrate you are printing on. High frequency images (one
> with
> >fine detail) usually benefit from a higher printer dpi, but it is subtle
> >when compared to 1440.
> >
> >Also the amount of ink put down at 2880 may worsen the print quality if the
> >ink cannot be absorbed into the substrate easily or tends to pool. And
> >different inks can come into play as well; I assume you are using Epson OEM
> >pigs.
> >
> >One would suppose that your 2000P should provide better results though than
> >a 4 headed printer at the same dpi.
> >
> >Perhaps one of our real digital experts can explain this to us.
> >
> >Don
> >
> >
> >>  -----Original Message-----
> >>  From: Sandy King [mailto:sanking@clemson.edu]
> >>  Sent: Saturday, April 17, 2004 5:26 PM
> >>  To: alt-photo-process-l@sask.usask.ca
> >>  Subject: Print Quality
> >>
> >>  Should one expect to see much difference in print quality between a
> >>  printer rated at 5760 X 1440 dpi and one rated at 2440 X 1440 dpi?
> >>
> >>  Sandy King
>
Received on Sun Apr 18 01:06:59 2004