How to increase dpi??

Discussion in 'Photoshop Tutorials' started by LoShue, Aug 31, 2003.

  1. LoShue

    LoShue Guest

    I have a jpg image which has 230 dpi. Can anyone advise how I can increase
    the dpi of that image to 300 or more? Thanks.
     
    LoShue, Aug 31, 2003
    #1
    1. Advertisements

  2. LoShue

    J Stafford Guest

    Let me be the one to break this in a gentle way. :) There is no such thing
    as DPI. But you mean pixels-per-(inch,cm,mm,whatever) and the answer is a
    qualified Yes. Yes, you can add pixels. Just reset the Image Size. BUT you
    will not increase 'resolution', per se. You cannot add detail that is not
    there in the original.
     
    J Stafford, Sep 1, 2003
    #2
    1. Advertisements

  3. LoShue

    Eric Gill Guest

    (J Stafford) wrote in
    And upsampling tends to damage the image. If you have been told you need a
    higher-rez image and you have no way of getting one without upsampling,
    just tell them this is the best you've got.
     
    Eric Gill, Sep 1, 2003
    #3
  4. LoShue

    edjh Guest

    Your image does not have 230 dpi. That is a fictional number. You can go
    to Image>Image Size and increase to 300 dpi with Resampling OFF but you
    will still have the same number of pixels. The "physical size" will
    appear smaiier.
     
    edjh, Sep 1, 2003
    #4
  5. LoShue

    Peter Guest

    Surely the Dpi or Ppi reading refers to the picture at the stated size. So
    that changing the resolution without resampling results in a smaller image.
    I know that when I have a large image and need to resize for a magazine
    picture I ask for the size at which it will be published and then resize to
    that leaving the resolution to increase to the maximum the new size will
    allow. It always works in practice but am I totally wrong?
    And of course referring back to an earlier reply. Dpi does exist - once the
    image goes to print.
    Cheers,
    Peter
     
    Peter, Sep 1, 2003
    #5
  6. Yes, you are. You should not allow the resolution to increase above the
    resolution the magazine is printed at, because it only means you are
    sending a too large file. The printing resolution is normally 300 dpi.
    If needed, you SHOULD resample to downsize the image to the requested
    size @ 300 dpi.
     
    Johan W. Elzenga, Sep 1, 2003
    #6
  7. LoShue

    edjh Guest

    Once you go to print. But you have to be clear that the picture consists
    of a set amount of pixels. Resampling will add or throw out pixels but
    can only degrade picture quality. Size expressed in anything other than
    the pixel dimensions is a fiction. There are no inches, centimeters,
    etc. in the computer.
     
    edjh, Sep 1, 2003
    #7
  8. I should have said s-spline - they have a gallery at the webiste also.
     
    Adrian McKenna, Sep 2, 2003
    #8
  9. LoShue

    Peter Guest

    Thanks for that. Just to clarify one point. Does resampling down also
    degrade the quality?
    Peter
     
    Peter, Sep 2, 2003
    #9
  10. LoShue

    Eric Gill Guest

    The technical answer is "yes", as you are throwing out information.
    Downsampling also tends to blur the image.

    However, if you are downsampling to hit the target resolution of an output
    device (and you do it properly), you will not be able to tell the
    difference. I do so all the time with the magazines I produce and it makes
    for much smaller files, a big time saver in transmitting and outputting the
    files.

    Further, remember that downsampling is a one way trip. If there is any
    possibility you will need to output that image again at a larger size, keep
    a copy of the original.
     
    Eric Gill, Sep 2, 2003
    #10
  11. LoShue

    Rogier Guest

    S-Spline might be just what you need. Check out the demo version here:
    http://www.shortcut.nl/redirect.php?page=downloads.product&id=ssplinepro

    Simply change the 230 dpi to 300 and check out the result. If you like
    it, you have to register the program to save it :)
     
    Rogier, Sep 2, 2003
    #11
  12. LoShue

    Peter Guest

    Many Thanks,
    Peter
     
    Peter, Sep 2, 2003
    #12
  13. LoShue

    Eric Gill Guest

    You bet.

    Something I left out, though - downsampling doesn't add the artifacting
    that upsampling does. It's safe to do when the application would benefit
    from it.
     
    Eric Gill, Sep 3, 2003
    #13
  14. LoShue

    itachi

    Joined:
    Nov 9, 2009
    Messages:
    1
    Likes Received:
    0
    Hi,

    I know this post is outdated, but I had the same problem and searched for quite some time for an answer. So for all those out there with images with low dpi..
    Try this: dpiguy.com.
    I had to increase the dpi for my figures for a scientific paper. You can upload your images there and they provide them back as 300 dpi increasing the resolution. Whenever I tried increasing the dpi my images shrank.

    cheers.
     
    itachi, Nov 9, 2009
    #14
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.