Camera 72dpi --> Print 300dpi

Discussion in 'Digital Photography' started by thomas, Feb 27, 2004.

  1. thomas

    thomas Guest

    I'm a little confused as what methods I should be using to print. I'm quite
    familiar with web graphics, but printing is something different.

    I just purchased a Canon i965 photo printer. Let's say my camera took this
    image

    http://img2.dpreview.com/gallery/canoneos300d_samples2/originals/030912-1336
    -50.jpg (2048x3072px).....

    If I open this image in Photoshop 7, and print. The resulting print off is
    very very blocky. However, if I resample this image in photoshop to 300
    pixels per inch, then the print comes out fine. I'm just totally confused
    tho how to control the size of the image. For example, lets say I wanted to
    get the above image printed (best fit) onto A4 size photo paper, I'm not too
    sure the right way to go about it.

    thomas
    thomas, Feb 27, 2004
    #1
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  2. thomas

    al-Farrob Guest

    thomas wrote:

    > I'm a little confused as what methods I should be using to print. I'm
    > quite familiar with web graphics, but printing is something different.
    >
    > I just purchased a Canon i965 photo printer. Let's say my camera took this
    > image
    >
    >

    http://img2.dpreview.com/gallery/canoneos300d_samples2/originals/030912-1336
    > -50.jpg (2048x3072px).....
    >
    > If I open this image in Photoshop 7, and print. The resulting print off is
    > very very blocky. However, if I resample this image in photoshop to 300
    > pixels per inch, then the print comes out fine. I'm just totally confused
    > tho how to control the size of the image. For example, lets say I wanted
    > to get the above image printed (best fit) onto A4 size photo paper, I'm
    > not too sure the right way to go about it.
    >
    > thomas


    Let's say 300 dpi is normally accepted almost as a standard for printing
    But if you come down to 200 dpi, it will not be that bad.
    More than 300 dpi is useless.
    Nothing like try and error, though :)

    --
    al-Farrob
    --
    http://www.al-farrob.com
    al-Farrob, Feb 27, 2004
    #2
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  3. thomas

    Jim Townsend Guest

    thomas wrote:

    > I'm a little confused as what methods I should be using to print. I'm quite
    > familiar with web graphics, but printing is something different.
    >
    > I just purchased a Canon i965 photo printer. Let's say my camera took this
    > image
    >
    > http://img2.dpreview.com/gallery/canoneos300d_samples2/originals/030912-1336
    > -50.jpg (2048x3072px).....
    >
    > If I open this image in Photoshop 7, and print. The resulting print off is
    > very very blocky. However, if I resample this image in photoshop to 300
    > pixels per inch, then the print comes out fine. I'm just totally confused
    > tho how to control the size of the image. For example, lets say I wanted to
    > get the above image printed (best fit) onto A4 size photo paper, I'm not too
    > sure the right way to go about it.


    Pixels per inch PPI (often called dots per inch DPI) is probably the most
    misunderstood aspect of digital photography.

    Despite being SO simple ;-)

    For example.. If you have an image that's 1000 pixels across, and you
    print it 10 inches wide on paper, then you've spread 1000 pixels across
    10 inches of paper.

    As a result, 100 pixels go into making up each inch of the printed image.

    Or in other words, you've just printed at 100 pixels per inch. There
    HAS to be 100 pixels in each inch. There CAN'T be anything else.

    Here's the math.. 1000 pixels / 10 inches = 100 pixels per inch

    PPI in this case is a printing term. It's the relationship between the
    number of pixels in the X and Y axis of the image and, the physical
    dimensions of the image when it's printed on the paper.

    If you have a 3072 pixel wide file, and you want to print it at
    300 PPI, then 3072 pixels / 300 PPI = 10.4 inches.

    A 3072 pixel wide file printed at 300 PPI MUST be 10.4 inches wide.
    It simply can't be anything else.

    That's IT ! There's no more to know about pixels per inch.

    ---

    Now. To answer your question. You say when you print an image, it's
    blotchy.. HOW are you printing it, how big are you printing it.. And
    most importantly.. DO YOU HAVE [RESAMPLE IMAGE] CHECKED ?

    If you have 'resample image' checked, -and- you set the Inches and PPI
    to some fixed value, then you are *no longer* printing a 2048 x 3072 file.

    Try this.. Load the 2048 x 3072 picture you showed a link to.

    With 'Resample image' checked, set your document size to 6 inches wide
    and 4 inches high at 72 PPI..

    NOTE.. Your image has just shrunk !!

    It is now only 432 pixels by 288 pixels. You've just told Photoshop
    you want to print 6 inches wide with 72 pixels making up each inch.

    Photoshop reduced the number of pixels in the image to accommodate your
    request. Unfortunately, a great deal of image information was lost.

    You are no longer printing out the full sized image. You just changed
    a 6.0 Mp image to a 0.12 Mp image. Will it print blotchy ? You bet :)

    Now uncheck the 'Resample Image' box.. NOTE that the Pixel Dimensions
    in 'Image Size' just grayed out. If you go into the Document settings
    and with your 2048 x 3072 image, set the document size to 4 x 6 inches,
    you'll see the PPI changes to 512..

    3072 pixels / 512 pixels per inch = 6 inches.. See.. All Photoshop is
    doing now is the simple math required to calculate PPI.

    Spreading 3072 pixels across 6 inches must result in 512 pixels being
    deposited in every inch.

    Bottom Line:

    When printing, make sure your resample image box is UNCHECKED.
    That way you will get the maximum number of pixels possible for
    each inch of paper.

    Always remember.. When you change your PPI with Resample checked,
    you are doing TWO things.. You're setting PPI -- AND -- you're
    changing the number of pixels in the file.

    This is probably what makes the concept so confusing :)

    --

    One last thing.. If you want to take your 1000 pixel image and print
    it 10 inches wide at 300 PPI, you can.. But remember, it involves
    changing the number of pixels in the file. (Otherwise it's
    mathematically impossible).

    Now if 'resample' is on and and you set the 1000 pixel wide image to
    print 10 inches wide at 300 PPI, it will interpolate the image
    and create the extra pixels required. The 1000 pixel wide image
    will now be 3000 pixels wide.

    The 3000 pixels spread over 10 inches = 300 PPI. In this case, it's
    good because you made the image bigger.

    Note, you are not *gaining* any picture information doing this and if
    you save the file, it will be larger.. But.. It can result in a slightly
    smoother printout.
    Jim Townsend, Feb 27, 2004
    #3
  4. On Fri, 27 Feb 2004 17:42:46 -0600, Jim Townsend wrote:

    > If you have a 3072 pixel wide file, and you want to print it at 300 PPI,
    > then 3072 pixels / 300 PPI = 10.4 inches.
    >
    > A 3072 pixel wide file printed at 300 PPI MUST be 10.4 inches wide. It
    > simply can't be anything else.
    >
    > That's IT ! There's no more to know about pixels per inch.


    That *should* be it. However, some clueless so and so put a "DPI" field in
    the JPEG header, which much software uses as a "hint". So people get
    confused, because they say "my camera produces an xyz dpi jpeg". This is
    of course total rubbish, as size in inches is not really an attribute
    digital images possess until printed, but is still confuses the life out
    of people.

    Canon cameras typically seem to set this field to 180dpi. It's utterly
    meaningless, but if you try to print with stupid software, the print will
    end up being sized around 180dpi.

    Mike.
    Mike Brodbelt, Feb 28, 2004
    #4
  5. thomas

    thomas Guest

    "Jim Townsend" <> wrote in message
    news:...
    > thomas wrote:
    >


    >
    > Bottom Line:
    >
    > When printing, make sure your resample image box is UNCHECKED.
    > That way you will get the maximum number of pixels possible for
    > each inch of paper.


    thanks for all that, it was very very helpful!

    Just one last question, if printing at 512 or 300, would I notice a
    difference in the output quality? or are the values too high to notice?
    thomas, Feb 28, 2004
    #5
  6. thomas

    Rabid Guest

    Jim this is one of the best explanations I've seen. I too have always
    struggled to comprehend this. Its not been a problem in the past as I just
    printed any old way and left the software to it. For some reason got better
    prints by putting an image in to word re sizing and printing from there!

    Thanks for taking the time. P

    "Jim Townsend" <> wrote in message
    news:...
    > thomas wrote:
    >
    > > I'm a little confused as what methods I should be using to print. I'm

    quite
    > > familiar with web graphics, but printing is something different.
    > >
    > > I just purchased a Canon i965 photo printer. Let's say my camera took

    this
    > > image
    > >
    > >

    http://img2.dpreview.com/gallery/canoneos300d_samples2/originals/030912-1336
    > > -50.jpg (2048x3072px).....
    > >
    > > If I open this image in Photoshop 7, and print. The resulting print off

    is
    > > very very blocky. However, if I resample this image in photoshop to 300
    > > pixels per inch, then the print comes out fine. I'm just totally

    confused
    > > tho how to control the size of the image. For example, lets say I wanted

    to
    > > get the above image printed (best fit) onto A4 size photo paper, I'm not

    too
    > > sure the right way to go about it.

    >
    > Pixels per inch PPI (often called dots per inch DPI) is probably the most
    > misunderstood aspect of digital photography.
    >
    > Despite being SO simple ;-)
    >
    > For example.. If you have an image that's 1000 pixels across, and you
    > print it 10 inches wide on paper, then you've spread 1000 pixels across
    > 10 inches of paper.
    >
    > As a result, 100 pixels go into making up each inch of the printed image.
    >
    > Or in other words, you've just printed at 100 pixels per inch. There
    > HAS to be 100 pixels in each inch. There CAN'T be anything else.
    >
    > Here's the math.. 1000 pixels / 10 inches = 100 pixels per inch
    >
    > PPI in this case is a printing term. It's the relationship between the
    > number of pixels in the X and Y axis of the image and, the physical
    > dimensions of the image when it's printed on the paper.
    >
    > If you have a 3072 pixel wide file, and you want to print it at
    > 300 PPI, then 3072 pixels / 300 PPI = 10.4 inches.
    >
    > A 3072 pixel wide file printed at 300 PPI MUST be 10.4 inches wide.
    > It simply can't be anything else.
    >
    > That's IT ! There's no more to know about pixels per inch.
    >
    > ---
    >
    > Now. To answer your question. You say when you print an image, it's
    > blotchy.. HOW are you printing it, how big are you printing it.. And
    > most importantly.. DO YOU HAVE [RESAMPLE IMAGE] CHECKED ?
    >
    > If you have 'resample image' checked, -and- you set the Inches and PPI
    > to some fixed value, then you are *no longer* printing a 2048 x 3072 file.
    >
    > Try this.. Load the 2048 x 3072 picture you showed a link to.
    >
    > With 'Resample image' checked, set your document size to 6 inches wide
    > and 4 inches high at 72 PPI..
    >
    > NOTE.. Your image has just shrunk !!
    >
    > It is now only 432 pixels by 288 pixels. You've just told Photoshop
    > you want to print 6 inches wide with 72 pixels making up each inch.
    >
    > Photoshop reduced the number of pixels in the image to accommodate your
    > request. Unfortunately, a great deal of image information was lost.
    >
    > You are no longer printing out the full sized image. You just changed
    > a 6.0 Mp image to a 0.12 Mp image. Will it print blotchy ? You bet :)
    >
    > Now uncheck the 'Resample Image' box.. NOTE that the Pixel Dimensions
    > in 'Image Size' just grayed out. If you go into the Document settings
    > and with your 2048 x 3072 image, set the document size to 4 x 6 inches,
    > you'll see the PPI changes to 512..
    >
    > 3072 pixels / 512 pixels per inch = 6 inches.. See.. All Photoshop is
    > doing now is the simple math required to calculate PPI.
    >
    > Spreading 3072 pixels across 6 inches must result in 512 pixels being
    > deposited in every inch.
    >
    > Bottom Line:
    >
    > When printing, make sure your resample image box is UNCHECKED.
    > That way you will get the maximum number of pixels possible for
    > each inch of paper.
    >
    > Always remember.. When you change your PPI with Resample checked,
    > you are doing TWO things.. You're setting PPI -- AND -- you're
    > changing the number of pixels in the file.
    >
    > This is probably what makes the concept so confusing :)
    >
    > --
    >
    > One last thing.. If you want to take your 1000 pixel image and print
    > it 10 inches wide at 300 PPI, you can.. But remember, it involves
    > changing the number of pixels in the file. (Otherwise it's
    > mathematically impossible).
    >
    > Now if 'resample' is on and and you set the 1000 pixel wide image to
    > print 10 inches wide at 300 PPI, it will interpolate the image
    > and create the extra pixels required. The 1000 pixel wide image
    > will now be 3000 pixels wide.
    >
    > The 3000 pixels spread over 10 inches = 300 PPI. In this case, it's
    > good because you made the image bigger.
    >
    > Note, you are not *gaining* any picture information doing this and if
    > you save the file, it will be larger.. But.. It can result in a slightly
    > smoother printout.
    >
    >
    Rabid, Feb 28, 2004
    #6
  7. thomas

    al-Farrob Guest

    al-Farrob, Feb 28, 2004
    #7
  8. thomas

    Don Stauffer Guest

    The exact method of resizing is a bit different from program to program,
    but the best bet is usually to set desired physical size first (i.e, 8 x
    10), and then check ppi. Adjust ppi to desired value (200-300ppi).
    Then be sure to RECHECK physical size. Some software has an interaction
    to these changes, and will change on when you change the other, but you
    can force it to whatever you want. So be sure to check both before
    actually selecting the print command.

    thomas wrote:
    >
    > I'm a little confused as what methods I should be using to print. I'm quite
    > familiar with web graphics, but printing is something different.
    >
    > I just purchased a Canon i965 photo printer. Let's say my camera took this
    > image
    >
    > http://img2.dpreview.com/gallery/canoneos300d_samples2/originals/030912-1336
    > -50.jpg (2048x3072px).....
    >
    > If I open this image in Photoshop 7, and print. The resulting print off is
    > very very blocky. However, if I resample this image in photoshop to 300
    > pixels per inch, then the print comes out fine. I'm just totally confused
    > tho how to control the size of the image. For example, lets say I wanted to
    > get the above image printed (best fit) onto A4 size photo paper, I'm not too
    > sure the right way to go about it.
    >
    > thomas


    --
    Don Stauffer in Minnesota

    webpage- http://www.usfamily.net/web/stauffer
    Don Stauffer, Feb 28, 2004
    #8
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