eugene wrote:
> Someone has asked me to give them an image with 350 dots per inch. Is this
> the same as 350 pixels per inch?
>
> thanks
>
>
There will be no doubt another long debate about ppi vs. dpi, but yes if
they asked for 350 dots per inch it is a very good bet that what they
really meant was 350 pixels per inch.
Scott W added these comments in the current discussion du jour
....
> eugene wrote:
>> Someone has asked me to give them an image with 350 dots per
>> inch. Is this the same as 350 pixels per inch?
>>
>
> There will be no doubt another long debate about ppi vs. dpi,
> but yes if they asked for 350 dots per inch it is a very good
> bet that what they really meant was 350 pixels per inch.
>
re: another long debate. I think you may be right here, Scott! As
best I can tell, the term DPI originated in the printing industry
for the earliest of what we now know as half-tone printing, which
is the laying down of a pattern of "dots" in a geometrically
regular pattern at an angle, often 45 degrees. In the days of B &
W newspapers, the number and size of the "dots" laid down roughly
to approximate the shades of gray in a continuous tone photo of
the day allowed the black dots and white news print to fool the
human eye into thinking they were looking at a real photo.
Later, the same idea was applied to color photos.
Much, much later, when computer scanners were invented, the term
DPI now had real meaning, in that it specified how many "dots"
the user wanted the scanner to "sample" or scan per linear inch
across the paper and down its length. Each "dot" resulted in a
pixel in the final image. AFAIK, that definition of "DPI" is
still valid.
I won't go into the debate about DPI for ink jet printers except
to say that the number of "dots" laid down by the printer in
order to "dither" to get the desired colors and density isn't at
all the same sort of definition I used above. Yes, of course the
printer is actually producing N DPI but it seems difficult for
them that aren't mathematicians to understand what is really
happening.
For us normal folk, who just want to get "good" prints from a
given pixel resolution raster graphics image, I agree with you
and most others in that "DPI" really means "PPI". I do not get
any of my images printed by pro shops nor do I dabble in
"printing" my images in publications that use today's version of
half-tone printing, but I suppose there are places that are set
up to calculate the finished print size using "DPI". One can
obviously do the exact same thing using "PPI" but perhaps older
print machines and/or older software may want DPI.
HEMI-Powered wrote:
> Scott W added
>>eugene wrote:
>>
>>>Someone has asked me to give them an image with 350 dots per
>>>inch. Is this the same as 350 pixels per inch?
>>
>>There will be no doubt another long debate about ppi vs. dpi,
>>but yes if they asked for 350 dots per inch it is a very good
>>bet that what they really meant was 350 pixels per inch.
There can only be one interpretation if asked for a digital file. It
would only mean printer dot resolution if the request was for a paper print.
> re: another long debate. I think you may be right here, Scott! As
> best I can tell, the term DPI originated in the printing industry
> for the earliest of what we now know as half-tone printing, which
> is the laying down of a pattern of "dots" in a geometrically
> regular pattern at an angle, often 45 degrees. In the days of B &
> W newspapers, the number and size of the "dots" laid down roughly
> to approximate the shades of gray in a continuous tone photo of
> the day allowed the black dots and white news print to fool the
> human eye into thinking they were looking at a real photo.
Interestingly, half-tone requires a huge resolution in digital files
because it's based on the photographic process of developing through a
screen with a grid of holes... with a film transparency overlaid. The
brighter areas burn each dot down to a smaller dot, the dark areas make
bigger black dots. And it's measured in lpi (lines per inch) just to
make things more confusing... halftones can also be done with lines
where the line simply gets fatter or thinner according to the exposure.
Digital is not good at achieving this because digital can only jump by
full pixels and cannot make gradual size increments like film.
> Later, the same idea was applied to color photos.
>
> Much, much later, when computer scanners were invented, the term
> DPI now had real meaning, in that it specified how many "dots"
> the user wanted the scanner to "sample" or scan per linear inch
> across the paper and down its length. Each "dot" resulted in a
> pixel in the final image. AFAIK, that definition of "DPI" is
> still valid.
>
> I won't go into the debate about DPI for ink jet printers except
> to say that the number of "dots" laid down by the printer in
> order to "dither" to get the desired colors and density isn't at
> all the same sort of definition I used above. Yes, of course the
> printer is actually producing N DPI but it seems difficult for
> them that aren't mathematicians to understand what is really
> happening.
>
> For us normal folk, who just want to get "good" prints from a
> given pixel resolution raster graphics image, I agree with you
> and most others in that "DPI" really means "PPI". I do not get
> any of my images printed by pro shops nor do I dabble in
> "printing" my images in publications that use today's version of
> half-tone printing, but I suppose there are places that are set
> up to calculate the finished print size using "DPI". One can
> obviously do the exact same thing using "PPI" but perhaps older
> print machines and/or older software may want DPI.
>
> And with that, let the debate begin!
Don Stauffer in Minnesota wrote:
> On Sep 19, 7:49 am, bugbear <bugbear@trim_papermule.co.uk_trim> wrote:
>
>
>>You didn't mention the correct units for sensor resolution ;-)
>>
>> BugBear
>
>
> Which I would say would be "samples per inch."
How about "sensel pitch", usually stated in nanometres (nm)?
I think it depends on the manufacturer, as this seems to be rarely
described as a feature of a camera's sensor by most manuafacturers, some
describe it also as a "pixel pitch", it's usually only described with an
overall megapixel (mp) rating and it's inch-size (as in: 2/3") or crop
factor (as in: 1.5x).
On Sep 19, 8:27 am, dj_nme <dj_...@hotmail.com> wrote:
> Don Stauffer in Minnesota wrote:
>
> > On Sep 19, 7:49 am, bugbear <bugbear@trim_papermule.co.uk_trim> wrote:
>
> >>You didn't mention the correct units for sensor resolution ;-)
>
> >> BugBear
>
> > Which I would say would be "samples per inch."
>
> How about "sensel pitch", usually stated in nanometres
> (nm)?
I think you meant micrometers ( AKA microns ), 0.000001 meters.
In article <Zd9Ii.9124$z_5.8493@nlpi069.nbdc.sbc.com>, paul-@-edgehill.net
says...
>There can only be one interpretation if asked for a digital file. It
>would only mean printer dot resolution if the request was for a paper print.
The first sentence above is correct, dpi can only mean pixels per inch there.
The second is not correct, or at least is quite hasty and rather incomplete.
There can only be one interpretation of dpi as concerning any image file, at
least if from a scanner or a camera, any and all those images we have to work
with. Both terms dpi or ppi are only about paper, because the only place
inches exist is on the paper. Regarding images, all inches are on paper.
Technically, the image file only has pixels.
Certainly the term can never mean ink drops if about image files. There are
no dithered ink drops in image files, which I think was your meaning. But we
do print those image files to our printers too, at perhaps 300 dpi, meaning
pixels per inch on paper. Then after inside the printer, there may be
another definition that comes into play to create the ink drops to do that
job of printing 300 pixels per inch on paper.
This whole notion of sematics about dpi is really dumb. For example, my big
dictionary has 116 definitions for the word "set". First one is to put
something in a particular place, and the last one is stubborn or obstinate.
The analogy is that some of us (I do not mean you Paul, I think your
intentions were good, but I mean others in past days) are obstinate,
insisting words can only have one meaning, specifically insisting the only
possible valid definition is the one they are able to understand. And when
newbies figure out there are two definitions, some of them go crazy inventing
their own rules for the rest us to abide by. Which is nonsense, because in
the real world, image resolution has always been called dpi (meaning pixels
per inch), and always will be called dpi. Just a name, but that is simply
the name that has always been used. So much easier to just accept that it is
used, because it definitely is used.
Saying PPI is fine too, no problem at all with ppi, that is indeed what it
means, but we absolutely must understand it either way, ppi or dpi, because
we absolutely will hear it both ways. It is very much like the word "set"
too, we need to understand the usage context determines the meaning.
I do not argue about which is "correct". Both are correct. Ppi may be more
clear to newbies, use it if you wish, but the name of the term has always
been dpi, and it is fully correct too. Always has been.
I only argue that both terms are used with the same meaning.
The point being that the only correct answer to such questions is that it is
called both dpi and ppi, either one interchangeably. Pick one and use it
yourself, but understanding that both are used is essential, or else we don't
know much, and we will remain confused.
"eugene" <eugene@home.com.invalid> wrote in message
news:upednfyRr6VMQ23bnZ2dnUVZ8qminZ2d@bt.com...
> Someone has asked me to give them an image with 350 dots per inch. Is this
> the same as 350 pixels per inch?
>
> thanks
No. Which program are you using? You should be able to change it to whatever
they want without resizing.
On second thought, maybe they did mean they wanted it 350 pixels wide,. Is
it for web?
dots per inch? 
Linear Mode
