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dpi=ppi?

 
 
Jim Townsend
Guest
Posts: n/a
 
      12-12-2003
didi wrote:

> Thank you all for the answers. In my case I was talking about just a
> picture resolution for a scanner. I scanned a pic with 300 dpi setting
> and when I look at it in photoshop it says 96 ppi. I was wondering if
> it was screwed up.


Ha.. More confusion between DPI and PPI

Your Photoshop plugged in a default PPI value.. Unless it actually sees a
predefined PPI value when loading an image file it inserts a default. In your
case, your Photoshop inserted a value of 96. Some versions insert 72.

Note you can edit the PPI.. If you'd prefer the image to be 300 PPI, then just
type in 300. If you want it to be 172 PPI, the change it to 172. Easy huh

Be aware that if you scan a 6 inch wide document at 300 dpi, you get an image
that's 6" x 300 pixels = 1800 pixels wide.

This image has 1800 pixels, but there are *no pixels per inch*.. Yet.

PPI is meaningless until you actually print your image on paper. The *inch* in
pixels per 'inch' stands for an inch of paper.

When you set the PPI value in an image file, all you are doing is supplying
instructions for your printer. The actual number of pixels in the file and
their orientation and how they look are unchanged. PPI makes no difference on
how an image looks on a monitor.. PPI is *only* a printing term.

As mentioned, you are free to change your 96 pixels per inch to anything you
want. Changing this value will only effect the size of the image when printed
on paper.

A 1800 pixel wide image printed at 96 pixels per inch will be:

1800 inches / 96 pixels per inch = 18.75 inches wide.

At 300 pixels per inch, it will be:

1800 pixels / 300 pixels per inch = 6 inches wide..

You see.. PPI is only an instruction that lets printers know how big to print
an image. You can change it at will.


 
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imbsysop
Guest
Posts: n/a
 
      12-12-2003
On Fri, 12 Dec 2003 08:57:01 +1030, "Ray Murphy"
<(E-Mail Removed)> wrote:

>
>----------
>In article <brajjd$19jku$(E-Mail Removed)-berlin.de>, "Canopus"
><(E-Mail Removed)> wrote:
>
>
>>
>>"Ray Murphy" <(E-Mail Removed)> wrote in message
>>news:(E-Mail Removed)...
>>>
>>> ----------
>>> In article <(E-Mail Removed)>, Jim Townsend
>>> <(E-Mail Removed)> wrote:
>>>
>>>
>>> >Don Stauffer wrote:
>>> >
>>> >
>>> >> For a scanner, yes. However, some of us prefer the term Samples per
>>> >> Inch, spi, to avoid any confusion, using dpi strictly for printers, and
>>> >> ppi for image pixels per inch.
>>> >
>>> >This would be ideal.. It certainly would eliminate a lot of confusion.
>>>
>>> RM: It's interesting that while we in Australia have been using metric
>>> measures for a few decades, we prefer to use ppi and dpi rather than
>>> p/mm or d/mm. It's just as well too )
>>>
>>> Ray

>>
>>LOL...they are international standard speak.

>
>RM: They (PPI, DPI + SPI) are not international speak in Europe,
>although I'm not sure if they constitute the majority of countries-
>although it's pixels/cm (not pixels/mm as I mentioned above).
>Printing screeens in much of Europe have been Lines/cm for many years
>as well - probably ever since they or the metric or system was
>invented.


You should use some update here

I've never heard or seen anyone in the amateur digicam business here
(EU) use pixel/cm and I've been into digital picts for over 2 years
now .. in every discussion PPI/DPI is used .. dunno in the
professional world but I very much doubt it ..
& printing lines /cm in printing screens ?? never seen nor used that
in over 25 yrs of computer support so I wonder where you got this
somewhat pre-historic idea(s) ?

 
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Ray Murphy
Guest
Posts: n/a
 
      12-12-2003

----------
In article <(E-Mail Removed)>, Jim Townsend
<(E-Mail Removed)> wrote:


>didi wrote:
>
>> Thank you all for the answers. In my case I was talking about just a
>> picture resolution for a scanner. I scanned a pic with 300 dpi setting
>> and when I look at it in photoshop it says 96 ppi. I was wondering if
>> it was screwed up.

>
>Ha.. More confusion between DPI and PPI
>
>Your Photoshop plugged in a default PPI value.. Unless it actually sees a
>predefined PPI value when loading an image file it inserts a default. In
>your
>case, your Photoshop inserted a value of 96. Some versions insert 72.
>
>Note you can edit the PPI.. If you'd prefer the image to be 300 PPI, then
>just
>type in 300. If you want it to be 172 PPI, the change it to 172. Easy huh
>
>
>Be aware that if you scan a 6 inch wide document at 300 dpi, you get an image
>that's 6" x 300 pixels = 1800 pixels wide.
>
>This image has 1800 pixels, but there are *no pixels per inch*.. Yet.
>
>PPI is meaningless until you actually print your image on paper. The
>*inch* in pixels per 'inch' stands for an inch of paper.


RM: The term ppi becomes quite meaningful from the moment we see our
preferred term in Photoshop.
If however we prefer to think in terms of pixels/cm, then everything
makes sense when we see the dimensions of the image in that mode.
We could also think in terms of a monitor view - say 640 x 480 and
deal directly with pixels without any reference to inches or
centimetres, but in the final analysis pixels *always* have a certain
number per inch AND *always* have a certain number per centimetre.

>When you set the PPI value in an image file, all you are doing is supplying
>instructions for your printer.


RM: We are also telling ourselves (or any viewer of our document) how
big the image will be in terms of inches or centimetres etc if the
resolution is unchanged WHEN it is eventually printed.

>The actual number of pixels in the file and
>their orientation and how they look are unchanged. PPI makes no difference
>on how an image looks on a monitor.. PPI is *only* a printing term.


RM: I'd say a pre-printing term because we use actual dimensions in
printing (inches, mm or cm). For example if we had a 200 ppi image
which was 6 inches square and we wanted to print it on a B + W laser
printer with a halftone screen ruling of 100 LPI, we would output the
image at 300 dpi or 600 dpi on the average laser printer, or 1200 dpi
on the good ones. Pixels are not an issue at that stage, although we
DO need to have 2 pixels per halftone dot if we are using a line
screen, but that is decided and set before the document is saved in
Photoshop.
>
>As mentioned, you are free to change your 96 pixels per inch to anything you
>want. Changing this value will only effect the size of the image when
>printed
>on paper.
>
>A 1800 pixel wide image printed at 96 pixels per inch will be:
>
> 1800 inches / 96 pixels per inch = 18.75 inches wide.
>
>At 300 pixels per inch, it will be:
>
> 1800 pixels / 300 pixels per inch = 6 inches wide..


RM: Or 10 inches wide at 180ppi; or 5 inches wide at 360 ppi etc......
>
>You see.. PPI is only an instruction that lets printers know how big to
>print an image. You can change it at will.


RM: As mentioned above, it also helps us to visualise our job long
before it is ever printed.

Ray
 
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Ray Murphy
Guest
Posts: n/a
 
      12-12-2003

----------
In article <(E-Mail Removed)>, imbsysop
<(E-Mail Removed)> wrote:


>On Fri, 12 Dec 2003 08:57:01 +1030, "Ray Murphy"
><(E-Mail Removed)> wrote:
>
>>
>>----------
>>In article <brajjd$19jku$(E-Mail Removed)-berlin.de>, "Canopus"
>><(E-Mail Removed)> wrote:
>>
>>
>>>
>>>"Ray Murphy" <(E-Mail Removed)> wrote in message
>>>news:(E-Mail Removed)...
>>>>
>>>> ----------
>>>> In article <(E-Mail Removed)>, Jim Townsend
>>>> <(E-Mail Removed)> wrote:
>>>>
>>>>
>>>> >Don Stauffer wrote:
>>>> >
>>>> >
>>>> >> For a scanner, yes. However, some of us prefer the term Samples per
>>>> >> Inch, spi, to avoid any confusion, using dpi strictly for printers,

>and
>>>> >> ppi for image pixels per inch.
>>>> >
>>>> >This would be ideal.. It certainly would eliminate a lot of confusion.
>>>>
>>>> RM: It's interesting that while we in Australia have been using metric
>>>> measures for a few decades, we prefer to use ppi and dpi rather than
>>>> p/mm or d/mm. It's just as well too )
>>>>
>>>> Ray
>>>
>>>LOL...they are international standard speak.

>>
>>RM: They (PPI, DPI + SPI) are not international speak in Europe,
>>although I'm not sure if they constitute the majority of countries-
>>although it's pixels/cm (not pixels/mm as I mentioned above).
>>Printing screeens in much of Europe have been Lines/cm for many years
>>as well - probably ever since they or the metric or system was
>>invented.

>
>You should use some update here
>
>I've never heard or seen anyone in the amateur digicam business here
>(EU) use pixel/cm and I've been into digital picts for over 2 years
>now .. in every discussion PPI/DPI is used .. dunno in the
>professional world but I very much doubt it ..
>& printing lines /cm in printing screens ?? never seen nor used that
>in over 25 yrs of computer support so I wonder where you got this
>somewhat pre-historic idea(s) ?


RM: It's actually the standard in the printing industry, and has been
for many years.
It's quite important for users of digicams to know about halftone
screens if they ever want to reproduce their photos in printed books
or magazines because we NEED two pixels for every halftone dot.

Let's put it this way - if we have a nice looking 200 ppi pic which
looks great on an inkjet print, and we want to print it professionally
- it becomes only HALF it's size if printed at normal quality on a
press - or looks absolutely terrible if we don't use 2 pixels per
halftone dot.
This is occurring every day and digicam users are simply not aware of
it.

Ray




 
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imbsysop
Guest
Posts: n/a
 
      12-12-2003
On Fri, 12 Dec 2003 21:13:28 +1030, "Ray Murphy"
<(E-Mail Removed)> wrote:

>
>----------
>In article <(E-Mail Removed)>, imbsysop
><(E-Mail Removed)> wrote:
>
>
>>On Fri, 12 Dec 2003 08:57:01 +1030, "Ray Murphy"
>><(E-Mail Removed)> wrote:
>>
>>>
>>>----------
>>>In article <brajjd$19jku$(E-Mail Removed)-berlin.de>, "Canopus"
>>><(E-Mail Removed)> wrote:
>>>
>>>
>>>>
>>>>"Ray Murphy" <(E-Mail Removed)> wrote in message
>>>>news:(E-Mail Removed)...
>>>>>
>>>>> ----------
>>>>> In article <(E-Mail Removed)>, Jim Townsend
>>>>> <(E-Mail Removed)> wrote:
>>>>>
>>>>>
>>>>> >Don Stauffer wrote:
>>>>> >
>>>>> >
>>>>> >> For a scanner, yes. However, some of us prefer the term Samples per
>>>>> >> Inch, spi, to avoid any confusion, using dpi strictly for printers,

>>and
>>>>> >> ppi for image pixels per inch.
>>>>> >
>>>>> >This would be ideal.. It certainly would eliminate a lot of confusion.
>>>>>
>>>>> RM: It's interesting that while we in Australia have been using metric
>>>>> measures for a few decades, we prefer to use ppi and dpi rather than
>>>>> p/mm or d/mm. It's just as well too )
>>>>>
>>>>> Ray
>>>>
>>>>LOL...they are international standard speak.
>>>
>>>RM: They (PPI, DPI + SPI) are not international speak in Europe,
>>>although I'm not sure if they constitute the majority of countries-
>>>although it's pixels/cm (not pixels/mm as I mentioned above).
>>>Printing screeens in much of Europe have been Lines/cm for many years
>>>as well - probably ever since they or the metric or system was
>>>invented.

>>
>>You should use some update here
>>
>>I've never heard or seen anyone in the amateur digicam business here
>>(EU) use pixel/cm a ....snip

>
>RM: It's actually the standard in the printing industry, and has been
>for many years.
>It's quite important for users of digicams to know about halftone
>screens if they ever want to reproduce their photos in printed books
>or magazines because we NEED two pixels for every halftone dot.


I was merely trying to pointout that AFAIK people in EU were also
using PPI/DPI and *not* PPcm or DPcm ..

 
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Jan Brittenson
Guest
Posts: n/a
 
      12-12-2003


Ray Murphy wrote:

>
> RM: It's actually the standard in the printing industry, and has been
> for many years.
> It's quite important for users of digicams to know about halftone
> screens if they ever want to reproduce their photos in printed books
> or magazines because we NEED two pixels for every halftone dot.
>
> Let's put it this way - if we have a nice looking 200 ppi pic which
> looks great on an inkjet print, and we want to print it professionally
> - it becomes only HALF it's size if printed at normal quality on a
> press - or looks absolutely terrible if we don't use 2 pixels per
> halftone dot.
> This is occurring every day and digicam users are simply not aware of
> it.


But the question is whether the halftoner can actually _resolve_
both pixels, or whether it's merely an algorithmic data appetite.
If it can't resolve it, then you can resample the data to make
sure it's spatially large enough for the halftone engine to do
its job.

 
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Ray Murphy
Guest
Posts: n/a
 
      12-12-2003

----------
In article <(E-Mail Removed)>, imbsysop
<(E-Mail Removed)> wrote:


>On Fri, 12 Dec 2003 21:13:28 +1030, "Ray Murphy"
><(E-Mail Removed)> wrote:
>
>>
>>----------
>>In article <(E-Mail Removed)>, imbsysop
>><(E-Mail Removed)> wrote:
>>
>>
>>>On Fri, 12 Dec 2003 08:57:01 +1030, "Ray Murphy"
>>><(E-Mail Removed)> wrote:
>>>
>>>>
>>>>----------
>>>>In article <brajjd$19jku$(E-Mail Removed)-berlin.de>, "Canopus"
>>>><(E-Mail Removed)> wrote:
>>>>
>>>>
>>>>>
>>>>>"Ray Murphy" <(E-Mail Removed)> wrote in message
>>>>>news:(E-Mail Removed)...
>>>>>>
>>>>>> ----------
>>>>>> In article <(E-Mail Removed)>, Jim Townsend
>>>>>> <(E-Mail Removed)> wrote:
>>>>>>
>>>>>>
>>>>>> >Don Stauffer wrote:
>>>>>> >
>>>>>> >
>>>>>> >> For a scanner, yes. However, some of us prefer the term Samples per
>>>>>> >> Inch, spi, to avoid any confusion, using dpi strictly for printers,
>>>and
>>>>>> >> ppi for image pixels per inch.
>>>>>> >
>>>>>> >This would be ideal.. It certainly would eliminate a lot of

>confusion.
>>>>>>
>>>>>> RM: It's interesting that while we in Australia have been using metric
>>>>>> measures for a few decades, we prefer to use ppi and dpi rather than
>>>>>> p/mm or d/mm. It's just as well too )
>>>>>>
>>>>>> Ray
>>>>>
>>>>>LOL...they are international standard speak.
>>>>
>>>>RM: They (PPI, DPI + SPI) are not international speak in Europe,
>>>>although I'm not sure if they constitute the majority of countries-
>>>>although it's pixels/cm (not pixels/mm as I mentioned above).
>>>>Printing screeens in much of Europe have been Lines/cm for many years
>>>>as well - probably ever since they or the metric or system was
>>>>invented.
>>>
>>>You should use some update here
>>>
>>>I've never heard or seen anyone in the amateur digicam business here
>>>(EU) use pixel/cm a ....snip

>>
>>RM: It's actually the standard in the printing industry, and has been
>>for many years.
>>It's quite important for users of digicams to know about halftone
>>screens if they ever want to reproduce their photos in printed books
>>or magazines because we NEED two pixels for every halftone dot.

>
>I was merely trying to pointout that AFAIK people in EU were also
>using PPI/DPI and *not* PPcm or DPcm ..


RM: That is what I was trying to correct. The printing industry, which
has been using digital images long before digital cameras became
popular, have been using LPI (Lines per inch) or L/cm (Lines per cm)
for halftone screens - probably for about a hundred years.

In the last decade or so since Photoshop was invented, graphic artists
and printers around the world have been familiar with the requirement
of using 2 pixels for each halftone dot, and they simply *double* the
halftone resolution they will be using when preparing digital images.
This means that if they "think" in metric terms, they double the L/cm
of the halftone screen, to get pixels per cm; or of they "think" in
inches, they double the LPI of the halftone screen to be used, to get
the correct number of pixels per inch.

This means that an American printer or graphic artist who "thinks" in
inches, and who plans to print a job with a 120 line halftone screen
(120 LPI) will prepare the job in Photoshop at 240 pixels per inch
(PPI). A French or German graphic artist who "thinks" in metric will
be using a 47 line halftone screen (47 L/cm) for the same job and will
double that figure to get the corect number of pixels - in this case
94 pixels per cm.(P/cm)

It appears from the many articles on the net, that it is becoming less
popular to use the abbreviation "/ " in references to Lines per cm or
Pixels per cm (L/cm or P/cm) and a new series of abbreviations has
surfaced:
LPI + LPC (Lines per inch + cm)
PPI + PPC (Pixels per inch + cm)
DPI + DPC (Dots per inch + cm)
SPI + SPC (Samples per inch + cm)

One of my main points was that there IS no "international standard" of
ppi and dpi, but two standards - Metric and non-metric, and we don't
know which one is used more.
It is certainly the standard on a predominantly American newsgroup
where inches are still being used, but that may not be the case in
other newsgroups where people don't normally use imperial
measurements.

Ray






 
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Ray Murphy
Guest
Posts: n/a
 
      12-12-2003

----------
In article <(E-Mail Removed)-this.com>, Jan Brittenson
<(E-Mail Removed)-this.com> wrote:


>
>
>Ray Murphy wrote:
>
>>
>> RM: It's actually the standard in the printing industry, and has been
>> for many years.
>> It's quite important for users of digicams to know about halftone
>> screens if they ever want to reproduce their photos in printed books
>> or magazines because we NEED two pixels for every halftone dot.
>>
>> Let's put it this way - if we have a nice looking 200 ppi pic which
>> looks great on an inkjet print, and we want to print it professionally
>> - it becomes only HALF it's size if printed at normal quality on a
>> press - or looks absolutely terrible if we don't use 2 pixels per
>> halftone dot.
>> This is occurring every day and digicam users are simply not aware of
>> it.

>
>But the question is whether the halftoner can actually _resolve_
>both pixels, or whether it's merely an algorithmic data appetite.


RM: I don't know how much quality is being lost when high quality
reproductions are done, and pixel images are converted to halftone
dots, but when we see the beautiful work that printing presses
produce, it doesn't look like we are losing much.
Still, we know we are losing *something* in the printing process
because we are converting a continuous tone (or digital) image into a
mosaic.

>If it can't resolve it, then you can resample the data to make
>sure it's spatially large enough for the halftone engine to do
>its job.


RM: Yes, resampling is the only way to go, but unfortunately many
people with desktop scanners and digital cameras often destroy their
master image which holds much more information than their final image.
Here's what is happening in real life. People produce family history
books with lots of pictures inserted amongst the text. They print out
good looking proofs from their digital printers and then give their
disks or CD's to professional printers for high quality output.

A few things can then happen:
(1) The printer prints the job and the customer complains because the
photos look terrible (because they have "pixelated" due to an
insufficient number of pixels). The customer then discovers that the
printer could have fixed their job to some extent by resampling their
defective Tiffs, but cannot understand why the printer will not do it
all for no payment.

(2) The printer refuses to go ahead with the job because there are not
enough pixels to make good haftones, or tells the customer to go back
to the original scans which hold more information and use them. The
customer says this is a problem because a lot of work has gone into
retouching the photos, or they have hrown out the original larger
file.

(3) The printer FIXES the job by resampling all the defective Tiffs
and asks for no payment, or the customer is asked to pay the
additional cost before it is done, but thinks the printer is trying to
breach his contract or rip them off.

What should happen?
The home publisher should ascertain what printing screen will be used
on their job, and then make their FINAL SIZE pics at TWICE the PPI of
the haltone screen being used.

This means that if a printer is doing a publication on an offset press
on bond paper with say a 100 LPI screen, then the pics need to be made
at 200 PPI. This is typical also of the popular high speed digital B+W
laser printers which are used for low grade publications.

The industry standard for the supply of photos on disk for
professional printing is 300 PPI. This allows for good quality 150 LPI
halftone screens to be used, BUT if someone has some scans or digital
camera images which are to be used for HIGH QUALITY printing - such
as 200 LPI or 300 LPI, then they need their photos at FINAL SIZE to
have 400 or 600 PPI. If they don't have this, then their 300 PPI
images need to be resampled (and therefore degraded) in order to
print them.

Another reason for using the correct ratio of pixels to halftone dots
(2:1 up to 2.5:1) is that if we are using a laser printer at home, it
will sometimes REFUSE to print if the resolution is set too high (such
as 300 PPI).
Resampling will of course fix that problem, but most people would get
pretty annoyed if they had to go back and fix up all the pictures in a
job - especially if they were in a hurry to get it finished.

Just a reminder to any new users of digital images: Laser printers
always use a halftone screen to produce pictures, stipples or tonal
graduations, unlike inkjet printers which don't need them, so it pays
to find out what resolution (in LPI) your laser printer (B+W or
Colour) is using for the various jobs you do.
You may for example just want to print out a simple newsletter in B+W
at 85 LPI on your 600 DPI printer. In that case your pics ned to be
170 PPI (at same size).

Ray






 
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imbsysop
Guest
Posts: n/a
 
      12-12-2003

"Ray Murphy" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
>

snip ..
> >
> >I was merely trying to pointout that AFAIK people in EU were also
> >using PPI/DPI and *not* PPcm or DPcm ..

>
> RM: That is what I was trying to correct. The printing industry, which
> has been using digital images long before digital cameras became
> popular, have been using LPI (Lines per inch) or L/cm (Lines per cm)
> for halftone screens - probably for about a hundred years.


thnx for the extensive clarification but you got me kind of confused
'cos I have some friends who work in the (book)printing business and all I
hear them talk about are picas and points and inches .. never cm ..
all the printers I have used in our research institute over the years were
always "stepping" in fractions of inches never metric so I wonder if despite
that there is no international standard, there might very well be a de facto
usage standard after all ..? just FWIW


 
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didi
Guest
Posts: n/a
 
      12-12-2003
"Ray Murphy" <(E-Mail Removed)> wrote in message news:<(E-Mail Removed)>...
> ----------
> In article <(E-Mail Removed)>, Jim Townsend
> <(E-Mail Removed)> wrote:
>
>
> >didi wrote:
> >
> >> Thank you all for the answers. In my case I was talking about just a
> >> picture resolution for a scanner. I scanned a pic with 300 dpi setting
> >> and when I look at it in photoshop it says 96 ppi. I was wondering if
> >> it was screwed up.

> >
> >Ha.. More confusion between DPI and PPI
> >
> >Your Photoshop plugged in a default PPI value.. Unless it actually sees a
> >predefined PPI value when loading an image file it inserts a default. In
> >your
> >case, your Photoshop inserted a value of 96. Some versions insert 72.
> >
> >Note you can edit the PPI.. If you'd prefer the image to be 300 PPI, then
> >just
> >type in 300. If you want it to be 172 PPI, the change it to 172. Easy huh
> >
> >
> >Be aware that if you scan a 6 inch wide document at 300 dpi, you get an image
> >that's 6" x 300 pixels = 1800 pixels wide.
> >
> >This image has 1800 pixels, but there are *no pixels per inch*.. Yet.
> >
> >PPI is meaningless until you actually print your image on paper. The
> >*inch* in pixels per 'inch' stands for an inch of paper.

>
> RM: The term ppi becomes quite meaningful from the moment we see our
> preferred term in Photoshop.
> If however we prefer to think in terms of pixels/cm, then everything
> makes sense when we see the dimensions of the image in that mode.
> We could also think in terms of a monitor view - say 640 x 480 and
> deal directly with pixels without any reference to inches or
> centimetres, but in the final analysis pixels *always* have a certain
> number per inch AND *always* have a certain number per centimetre.
>
> >When you set the PPI value in an image file, all you are doing is supplying
> >instructions for your printer.

>
> RM: We are also telling ourselves (or any viewer of our document) how
> big the image will be in terms of inches or centimetres etc if the
> resolution is unchanged WHEN it is eventually printed.
>
> >The actual number of pixels in the file and
> >their orientation and how they look are unchanged. PPI makes no difference
> >on how an image looks on a monitor.. PPI is *only* a printing term.

>
> RM: I'd say a pre-printing term because we use actual dimensions in
> printing (inches, mm or cm). For example if we had a 200 ppi image
> which was 6 inches square and we wanted to print it on a B + W laser
> printer with a halftone screen ruling of 100 LPI, we would output the
> image at 300 dpi or 600 dpi on the average laser printer, or 1200 dpi
> on the good ones. Pixels are not an issue at that stage, although we
> DO need to have 2 pixels per halftone dot if we are using a line
> screen, but that is decided and set before the document is saved in
> Photoshop.
> >
> >As mentioned, you are free to change your 96 pixels per inch to anything you
> >want. Changing this value will only effect the size of the image when
> >printed
> >on paper.
> >
> >A 1800 pixel wide image printed at 96 pixels per inch will be:
> >
> > 1800 inches / 96 pixels per inch = 18.75 inches wide.
> >
> >At 300 pixels per inch, it will be:
> >
> > 1800 pixels / 300 pixels per inch = 6 inches wide..

>
> RM: Or 10 inches wide at 180ppi; or 5 inches wide at 360 ppi etc......
> >
> >You see.. PPI is only an instruction that lets printers know how big to
> >print an image. You can change it at will.

>
> RM: As mentioned above, it also helps us to visualise our job long
> before it is ever printed.
>
> Ray


Ok, I am not sure what I need to do now. For a specific goal, I need a
pic that's 300x300 pixels and I was told I needed to scan it with a
resolution of 150 dpi and the file size cannot exceed 62MB. How do I
do that?
 
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