Printer DPI

pjmoriarty.TakeThisOut@gmail.com wrote:
> Discussion Preface: a given printer is listed as having a dpi of
> 2400dpi x 1200dpi
>
> Question: If an inch is already a square unit of measure, what is the
> meaning of the second value?

It isn't, it's a linear inch. So the next two paragraphs are mostly
irrelevant.

> 2400dpi would mean (by my logic) that 2400 dots may fit in a given
> square inch...why then also a listing of 1200dpi?
>
> Are dots rectangular? are they stacked like bricks...allowing for more
> layers on the vertical axis of a given squared inch than on the
> horizontal?

A dot is a bit of one ink color. Of most importance -- a dot is *NOT* a
pixel; each dot can be one of the ink colors the printer has, and can
often be different sizes, but it *cannot* be all 16 million colors a
24-bit system can represent.
 >> Stay informed about: Printer DPI 

On Fri, 23 Mar 2007 15:15:34 -0700, pjmoriarty wrote:

> Discussion Preface: a given printer is listed as having a dpi of
> 2400dpi x 1200dpi
>
> Question: If an inch is already a square unit of measure, what is the
> meaning of the second value?

Answer: an inch is a linear unit of measure - the area measure is a square
inch. They're trying to tell you it does 2400 dots per inch in (probably)
the horizontal direction and 1200 dots per inch in the other - probably
vertical direction.

>
> 2400dpi would mean (by my logic) that 2400 dots may fit in a given
> square inch...why then also a listing of 1200dpi?

It does not say 2400 dots per square inch.

>
> Are dots rectangular? are they stacked like bricks...allowing for more
> layers on the vertical axis of a given squared inch than on the
> horizontal?

Dots are actually dots - they are round - but they are so small it doesn't
matter much. There are two stepping motors which control where dots are
placed - there is no reason why the vertical and horizontal should match
at all. One stepper pulls the head along in the horizontal direction, the
other pulls the paper by some fixed amount.

>
> If anyone is familiar with these conventions, please help. I'm finding
> this to be rather curious.
>
> PJ Moriarty
 >> Stay informed about: Printer DPI 

pjmoriarty.DeleteThis@gmail.com wrote in
news:1174688134.429862.5830@y80g2000hsf.googlegroups.com:

> Discussion Preface: a given printer is listed as having a dpi of
> 2400dpi x 1200dpi
>
> Question: If an inch is already a square unit of measure, what
> is the meaning of the second value?

Horizontal vs vertical, as I recall.

Not that either is actually a resolution.

--
"What is the first law?"
"To Protect."
"And the second?"
"Ourselves."

Terry Austin
 >> Stay informed about: Printer DPI 

This gets messy! <G>
An inkjet printer dot has a certain size, with variations due to paper, ink
amount, etc.
The dot rating by a printer mfr has to do with--
The vertical and horizontal positioning accuracy of the printer mechanism
(Usually, horizontal positioning is more accurate than vertical, but not
always, due to such things as bidirectional printing, and high speed
printing.)
The number and spacing of the ink nozzles on the head
which nozzles can be used and when

And you thought there was a simple answer!

For example a printer mechanism based positioning capability might be 360th
of an inch. The head has multiple nozzles that cannot be fired all at once,
but multiple nozzles can be fired.
Assuming that the spacing between nozzles is now the determing factor
(without moving the head) some number of dots can be printed in a pattern.
Assuming that the head is now moved one 360th of an inch. The new head
position plus which nozzles are fired determines the relative position of
the dots between the two head positions, previously printed dots, and such
things as the numbers in the "2400dpi x 1200dpi". Obviously, the head
positions overlap in the example.


How this actually happens in printing a page is a really involved process,
usually involving OEM algorithms and is generally not well documented, even
in some of the programmers guides. How a printer prints a specific color
other than that of the printers ink colors is another area that the OEMs
don't like to document for the rest of us.


There are some Epson documents somewhere on the web that lists the basic
printer command sequences that can be combined to print dot patterns up to
about 720 dpi.
Epson is carful to not document the higher resolutions that the printer
specs usually list.

"Jack Splat =(" <nospam.TakeThisOut@nospam.com> wrote in message
news:46046aac$0$14092$742ec2ed@news.sonic.net...
> <pjmoriarty.TakeThisOut@gmail.com> wrote in message
> news:1174688134.429862.5830@y80g2000hsf.googlegroups.com...
> > Discussion Preface: a given printer is listed as having a dpi of
> > 2400dpi x 1200dpi
> >
> > Question: If an inch is already a square unit of measure, what is the
> > meaning of the second value?
> >
> > 2400dpi would mean (by my logic) that 2400 dots may fit in a given
> > square inch...why then also a listing of 1200dpi?
> >
> > Are dots rectangular? are they stacked like bricks...allowing for more
> > layers on the vertical axis of a given squared inch than on the
> > horizontal?
> >
> > If anyone is familiar with these conventions, please help. I'm finding
> > this to be rather curious.
> >
> > PJ Moriarty
> >
>
>
> Also at least for HP the printer can use up to 36 dots to make one color.
> The ink is not opaque and the printer can layer them, overlap them by
> different amounts, etc. There was a really interesting program on one of
the
> educational channels (like Discovery, etc.) on the "How Its Made" show
about
> inks and they talked about how inks for inkjet printers are made and how
the
> printers use them. They dealt only with HP, but it was interesting.
>
> =(
>
 >> Stay informed about: Printer DPI 

<pjmoriarty.RemoveThis@gmail.com> wrote in message
news:1174688134.429862.5830@y80g2000hsf.googlegroups.com...
> Discussion Preface: a given printer is listed as having a dpi of
> 2400dpi x 1200dpi
>
> Question: If an inch is already a square unit of measure, what is the
> meaning of the second value?
>
> 2400dpi would mean (by my logic) that 2400 dots may fit in a given
> square inch...why then also a listing of 1200dpi?
>
> Are dots rectangular? are they stacked like bricks...allowing for more
> layers on the vertical axis of a given squared inch than on the
> horizontal?
>
> If anyone is familiar with these conventions, please help. I'm finding
> this to be rather curious.
>
> PJ Moriarty
>
It means 2400 columns and 1200 rows of dots in one square inch. Thus, a
given square inch has 2400 times 1200 dots.
Pixels are square. Dots are round.
Jim
 >> Stay informed about: Printer DPI 

"Jim" <j.n RemoveThis @nospam.com> wrote in message
news:boZMh.10290$Um6.4783@newssvr12.news.prodigy.net...
>
> <pjmoriarty RemoveThis @gmail.com> wrote in message
> news:1174688134.429862.5830@y80g2000hsf.googlegroups.com...
>> Discussion Preface: a given printer is listed as having a dpi of
>> 2400dpi x 1200dpi
>>
>> Question: If an inch is already a square unit of measure, what is the
>> meaning of the second value?
>>
>> 2400dpi would mean (by my logic) that 2400 dots may fit in a given
>> square inch...why then also a listing of 1200dpi?
>>
>> Are dots rectangular? are they stacked like bricks...allowing for more
>> layers on the vertical axis of a given squared inch than on the
>> horizontal?
>>
>> If anyone is familiar with these conventions, please help. I'm finding
>> this to be rather curious.
>>
>> PJ Moriarty
>>
> It means 2400 columns and 1200 rows of dots in one square inch. Thus, a
> given square inch has 2400 times 1200 dots.
> Pixels are square. Dots are round.
> Jim
>


Which is 2,880,000 dots per printer inch. That is a lot of dots in such a
small space. But, then since the HP's at least can need 36 dots of ink to
make on color I guess those 2,880,000 dots go pretty fast.

=(
 >> Stay informed about: Printer DPI 

On 23 Mar 2007 15:15:34 -0700
pjmoriarty.TakeThisOut@gmail.com wrote:

> Discussion Preface: a given printer is listed as having a dpi of
> 2400dpi x 1200dpi
>
> Question: If an inch is already a square unit of measure, what is the
> meaning of the second value?
An inch is a linear measure - a square inch is a measure of area.
>
> 2400dpi would mean (by my logic) that 2400 dots may fit in a given
> square inch...why then also a listing of 1200dpi?
Your logic is flawed.



--
Neil
Reverse 'r' and 'a', delete 'l' for email.
 >> Stay informed about: Printer DPI 

<pjmoriarty DeleteThis @gmail.com> wrote in message
news:1174688134.429862.5830@y80g2000hsf.googlegroups.com...
> Discussion Preface: a given printer is listed as having a dpi of
> 2400dpi x 1200dpi
>
> Question: If an inch is already a square unit of measure, what is the
> meaning of the second value?
>
> 2400dpi would mean (by my logic) that 2400 dots may fit in a given
> square inch...why then also a listing of 1200dpi?
>
> Are dots rectangular? are they stacked like bricks...allowing for more
> layers on the vertical axis of a given squared inch than on the
> horizontal?
>
> If anyone is familiar with these conventions, please help. I'm finding
> this to be rather curious.
>
> PJ Moriarty
>
An inch is a linear unit of measurement, not square.

--
Skip Middleton
www.shadowcatcherimagery.com
www.pbase.com/skipm
 >> Stay informed about: Printer DPI 

It's not my logic, it's the printer mfrs. Don't blame me if it stinks!
The carrage may increment horizontally in smaller steps than the paper can
be advanced vertically.
The 2:1 ratio goes back to that and that alone. (two horizontal steps = 1
vertical)

"Neil Ellwood" <cral.elllwood2 RemoveThis @btopenworld.com> wrote in message
news:20070324084754.08b1eee3@Games...
> On 23 Mar 2007 15:15:34 -0700
> pjmoriarty RemoveThis @gmail.com wrote:
>
> > Discussion Preface: a given printer is listed as having a dpi of
> > 2400dpi x 1200dpi
> >
> > Question: If an inch is already a square unit of measure, what is the
> > meaning of the second value?
> An inch is a linear measure - a square inch is a measure of area.
> >
> > 2400dpi would mean (by my logic) that 2400 dots may fit in a given
> > square inch...why then also a listing of 1200dpi?
> Your logic is flawed.
>
>
>
> --
> Neil
> Reverse 'r' and 'a', delete 'l' for email.
 >> Stay informed about: Printer DPI 

Dots can be stacked on top or overlapping. In addition, the size of the dots
can be changed. (ink bleeds)
"Skip" <shadowcatcher RemoveThis @cox.net> wrote in message
news:WJ9Nh.105761$6P2.21288@newsfe16.phx...
> <pjmoriarty RemoveThis @gmail.com> wrote in message
> news:1174688134.429862.5830@y80g2000hsf.googlegroups.com...
> > Discussion Preface: a given printer is listed as having a dpi of
> > 2400dpi x 1200dpi
> >
> > Question: If an inch is already a square unit of measure, what is the
> > meaning of the second value?
> >
> > 2400dpi would mean (by my logic) that 2400 dots may fit in a given
> > square inch...why then also a listing of 1200dpi?
> >
> > Are dots rectangular? are they stacked like bricks...allowing for more
> > layers on the vertical axis of a given squared inch than on the
> > horizontal?
> >
> > If anyone is familiar with these conventions, please help. I'm finding
> > this to be rather curious.
> >
> > PJ Moriarty
> >
> An inch is a linear unit of measurement, not square.
>
> --
> Skip Middleton
> www.shadowcatcherimagery.com
> www.pbase.com/skipm
>
>
 >> Stay informed about: Printer DPI 

On Mar 23, 6:28 pm, "Chuck" <Chuckk2nos....TakeThisOut@cox.net> wrote:
> This gets messy! <G>
> An inkjet printer dot has a certain size, with variations due to paper, ink
> amount, etc.

The fact that the dots may be different sizes on different paper is
known as dot gain. Many printer drivers and some photo editing
programs allow you to input a correction for dot gain to account for
this. See your printer manual and manual for the editor. Incorrect
values alter the contrast and gamma from what is shown on monitor, so
you essentially need to have a correction on this for every different
paper you use.
 >> Stay informed about: Printer DPI