Dots per inch question

"Swingman" wrote in message
...

(snip)

That is a very excellent explanation of the issue, however I
don't understand it in a practical way. To use your
example, is it best to resample an image to 3200x3600 @
300ppi if you wish to make a 10x12 print, or do the photo
apps handle this in the background before they send the data
to the printer?

-------------

So I have been told by others, and a view I tend to agree with, is that the
image should be resized in an image editor for the best control. Even there,
it is said to be something of a technical advantage to resize (where a
significant change in size is made) in several steps rather than in one big
jump. After the final resize there is also, if you are working in a proper
edit application, the probability that you will want to apply sharpening and
other tweaks before actually printing.

You CAN re-scale in the printer (most) but with little or no control simply
by telling the printer to print "full page" (or ANYTHING other than the
native 100% scaled image size - whether that might be a larger or smaller
value) and it will do that - such that you could take that example image of
1600x1800 @300ppi (5.3x6inches) and just tell the printer to print it (scale
it) to the full paper size. The printer may not actually resample beyond
just managing the image to (as if it were) a lower PPI value to make it fit.
Thus the 3,5x6 inch image you intended to print @300ppi will actually print
more like @120 - 150 because it is being stretched to fit the paper size.
The output quality will be affected if you do that.

Here is a general rule of thumb for printing (on you own printer as well as
sending images for commercial printing,) and that should always be done
before printing. Scale the image and image resolution to the full size
you want it to print at in an editor before printing. The printer is
then only being asked to do one thing - manage the ink as it is applied to
the paper but not manage the ink as well as also trying, at the same time,
to resample the image to make it fit (either adding additional data or
removing data that it can not use at the print settings you have selected =
resampling.)

ON A RELATED ISSUE...

Scanner gurus will also tell you that when scanning the same rule of thumb
applies - that is, to ALWAYS select the desired output size (inches/pixels)
and resolution (PPI) of the END USE output and then scan the original medium
to produce that file. Thus, scanning for only web use you can select a
resolution of 72ppi and at a physical size (scaled in pixels) to fit a
computer screen; but for printing you can (and should) select something
higher (150, 200, 300ppi resolutions) and at the native image size (100%
scaled in inches) it is to ultimately be printed. For our example image - to
make a scan for a nominal computer screen (see note) that will be 3.5x6
INCHES on screen, and assuming that many / most monitors will display at
72ppi then the 100% scaled image need only be 252pixels wide x 432pixels
long (instead of the 3.5x6 inches printing example of 1600x3200) and with
the obvious saving in image file size that results.

Note: As a computer screen can vary in two ways independent of the image
itself: physical dimension (14", 15", 17" ect) and by screen resolution (a
selectable value) the same image will not display at the same size on a
screen set to display 600x800pixels as on one set to 768x1024pixels... or...
on screens with different physical sizes from the one you work on, but even
where the screen pixel dimensions may be the same. Screen display should
always be thought of in pixels rather than inches. It is not a complex
problem but one that requires some thought and consideration in constructing
a web page.

Better?

Journalist

"Swingman" wrote in message
...

(snip)

That is a very excellent explanation of the issue, however I
don't understand it in a practical way. To use your
example, is it best to resample an image to 3200x3600 @
300ppi if you wish to make a 10x12 print, or do the photo
apps handle this in the background before they send the data
to the printer?

-------------

So I have been told by others, and a view I tend to agree with, is that the
image should be resized in an image editor for the best control. Even there,
it is said to be something of a technical advantage to resize (where a
significant change in size is made) in several steps rather than in one big
jump. After the final resize there is also, if you are working in a proper
edit application, the probability that you will want to apply sharpening and
other tweaks before actually printing.

You CAN re-scale in the printer (most) but with little or no control simply
by telling the printer to print "full page" (or ANYTHING other than the
native 100% scaled image size - whether that might be a larger or smaller
value) and it will do that - such that you could take that example image of
1600x1800 @300ppi (5.3x6inches) and just tell the printer to print it (scale
it) to the full paper size. The printer may not actually resample beyond
just managing the image to (as if it were) a lower PPI value to make it fit.
Thus the 3,5x6 inch image you intended to print @300ppi will actually print
more like @120 - 150 because it is being stretched to fit the paper size.
The output quality will be affected if you do that.

Here is a general rule of thumb for printing (on you own printer as well as
sending images for commercial printing,) and that should always be done
before printing. Scale the image and image resolution to the full size
you want it to print at in an editor before printing. The printer is
then only being asked to do one thing - manage the ink as it is applied to
the paper but not manage the ink as well as also trying, at the same time,
to resample the image to make it fit (either adding additional data or
removing data that it can not use at the print settings you have selected =
resampling.)

ON A RELATED ISSUE...

Scanner gurus will also tell you that when scanning the same rule of thumb
applies - that is, to ALWAYS select the desired output size (inches/pixels)
and resolution (PPI) of the END USE output and then scan the original medium
to produce that file. Thus, scanning for only web use you can select a
resolution of 72ppi and at a physical size (scaled in pixels) to fit a
computer screen; but for printing you can (and should) select something
higher (150, 200, 300ppi resolutions) and at the native image size (100%
scaled in inches) it is to ultimately be printed. For our example image - to
make a scan for a nominal computer screen (see note) that will be 3.5x6
INCHES on screen, and assuming that many / most monitors will display at
72ppi then the 100% scaled image need only be 252pixels wide x 432pixels
long (instead of the 3.5x6 inches printing example of 1600x3200) and with
the obvious saving in image file size that results.

Note: As a computer screen can vary in two ways independent of the image
itself: physical dimension (14", 15", 17" ect) and by screen resolution (a
selectable value) the same image will not display at the same size on a
screen set to display 600x800pixels as on one set to 768x1024pixels... or...
on screens with different physical sizes from the one you work on, but even
where the screen pixel dimensions may be the same. Screen display should
always be thought of in pixels rather than inches. It is not a complex
problem but one that requires some thought and consideration in constructing
a web page.

Better?

Journalist

"Journalist-North" wrote in message =
.uk...
=20
"Swingman" wrote in message
...
=20
(snip)

That is a very excellent explanation of the issue, however I
don't understand it in a practical way. To use your
example, is it best to resample an image to 3200x3600 @
300ppi if you wish to make a 10x12 print, or do the photo
apps handle this in the background before they send the data
to the printer?

-------------
=20
So I have been told by others, and a view I tend to agree with, is =
that the
image should be resized in an image editor for the best control. Even =
there,
it is said to be something of a technical advantage to resize (where a
significant change in size is made) in several steps rather than in =
one big
jump. After the final resize there is also, if you are working in a =
proper
edit application, the probability that you will want to apply =
sharpening and
other tweaks before actually printing.
=20
You CAN re-scale in the printer (most) but with little or no control =
simply
by telling the printer to print "full page" (or ANYTHING other than =
the
native 100% scaled image size - whether that might be a larger or =
smaller
value) and it will do that - such that you could take that example =
image of
1600x1800 @300ppi (5.3x6inches) and just tell the printer to print it =
(scale
it) to the full paper size. The printer may not actually resample =
beyond
just managing the image to (as if it were) a lower PPI value to make =
it fit.
Thus the 3,5x6 inch image you intended to print @300ppi will actually =
print
more like @120 - 150 because it is being stretched to fit the paper =
size.
The output quality will be affected if you do that.
=20
Here is a general rule of thumb for printing (on you own printer as =
well as
sending images for commercial printing,) and that should always be =
done
before printing. Scale the image and image resolution to the full =
size
you want it to print at in an editor before printing. The printer =
is
then only being asked to do one thing - manage the ink as it is =
applied to
the paper but not manage the ink as well as also trying, at the same =
time,
to resample the image to make it fit (either adding additional data or
removing data that it can not use at the print settings you have =
selected =3D
resampling.)
=20
ON A RELATED ISSUE...
=20
Scanner gurus will also tell you that when scanning the same rule of =
thumb
applies - that is, to ALWAYS select the desired output size =
(inches/pixels)
and resolution (PPI) of the END USE output and then scan the original =
medium
to produce that file. Thus, scanning for only web use you can select a
resolution of 72ppi and at a physical size (scaled in pixels) to fit a
computer screen; but for printing you can (and should) select =
something
higher (150, 200, 300ppi resolutions) and at the native image size =
(100%
scaled in inches) it is to ultimately be printed. For our example =
image - to
make a scan for a nominal computer screen (see note) that will be =
3.5x6
INCHES on screen, and assuming that many / most monitors will display =
at
72ppi then the 100% scaled image need only be 252pixels wide x =
432pixels
long (instead of the 3.5x6 inches printing example of 1600x3200) and =
with
the obvious saving in image file size that results.
=20
Note: As a computer screen can vary in two ways independent of the =
image
itself: physical dimension (14", 15", 17" ect) and by screen =
resolution (a
selectable value) the same image will not display at the same size on =
a
screen set to display 600x800pixels as on one set to 768x1024pixels... =
or...
on screens with different physical sizes from the one you work on, but =
even
where the screen pixel dimensions may be the same. Screen display =
should
always be thought of in pixels rather than inches. It is not a complex
problem but one that requires some thought and consideration in =
constructing
a web page.
=20
Better?
=20
Journalist

Yes, that IS better - thanks!

"Journalist-North" wrote in message =
.uk...
=20
"Swingman" wrote in message
...
=20
(snip)

That is a very excellent explanation of the issue, however I
don't understand it in a practical way. To use your
example, is it best to resample an image to 3200x3600 @
300ppi if you wish to make a 10x12 print, or do the photo
apps handle this in the background before they send the data
to the printer?

-------------
=20
So I have been told by others, and a view I tend to agree with, is =
that the
image should be resized in an image editor for the best control. Even =
there,
it is said to be something of a technical advantage to resize (where a
significant change in size is made) in several steps rather than in =
one big
jump. After the final resize there is also, if you are working in a =
proper
edit application, the probability that you will want to apply =
sharpening and
other tweaks before actually printing.
=20
You CAN re-scale in the printer (most) but with little or no control =
simply
by telling the printer to print "full page" (or ANYTHING other than =
the
native 100% scaled image size - whether that might be a larger or =
smaller
value) and it will do that - such that you could take that example =
image of
1600x1800 @300ppi (5.3x6inches) and just tell the printer to print it =
(scale
it) to the full paper size. The printer may not actually resample =
beyond
just managing the image to (as if it were) a lower PPI value to make =
it fit.
Thus the 3,5x6 inch image you intended to print @300ppi will actually =
print
more like @120 - 150 because it is being stretched to fit the paper =
size.
The output quality will be affected if you do that.
=20
Here is a general rule of thumb for printing (on you own printer as =
well as
sending images for commercial printing,) and that should always be =
done
before printing. Scale the image and image resolution to the full =
size
you want it to print at in an editor before printing. The printer =
is
then only being asked to do one thing - manage the ink as it is =
applied to
the paper but not manage the ink as well as also trying, at the same =
time,
to resample the image to make it fit (either adding additional data or
removing data that it can not use at the print settings you have =
selected =3D
resampling.)
=20
ON A RELATED ISSUE...
=20
Scanner gurus will also tell you that when scanning the same rule of =
thumb
applies - that is, to ALWAYS select the desired output size =
(inches/pixels)
and resolution (PPI) of the END USE output and then scan the original =
medium
to produce that file. Thus, scanning for only web use you can select a
resolution of 72ppi and at a physical size (scaled in pixels) to fit a
computer screen; but for printing you can (and should) select =
something
higher (150, 200, 300ppi resolutions) and at the native image size =
(100%
scaled in inches) it is to ultimately be printed. For our example =
image - to
make a scan for a nominal computer screen (see note) that will be =
3.5x6
INCHES on screen, and assuming that many / most monitors will display =
at
72ppi then the 100% scaled image need only be 252pixels wide x =
432pixels
long (instead of the 3.5x6 inches printing example of 1600x3200) and =
with
the obvious saving in image file size that results.
=20
Note: As a computer screen can vary in two ways independent of the =
image
itself: physical dimension (14", 15", 17" ect) and by screen =
resolution (a
selectable value) the same image will not display at the same size on =
a
screen set to display 600x800pixels as on one set to 768x1024pixels... =
or...
on screens with different physical sizes from the one you work on, but =
even
where the screen pixel dimensions may be the same. Screen display =
should
always be thought of in pixels rather than inches. It is not a complex
problem but one that requires some thought and consideration in =
constructing
a web page.
=20
Better?
=20
Journalist

Yes, that IS better - thanks!