Should File DPI Match Printer DPI?

Discussion in 'Digital Photography' started by DS, Jul 5, 2004.

  1. DS

    DS Guest

    I have a Hi-Ti 640 printer that has a native resolution of about 400
    dpi. Depending on various factors, the files I modify/create in
    Photoshop may have more or less dpi (most likely less). Is there any
    reason to keep the file and printer dpi somewhat equal? If not, are
    there any implictions regarding output quality? TIA

    Dale
     
    DS, Jul 5, 2004
    #1
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  2. DS

    Alex Butcher Guest

    If your camera has a resolution of 1600x1200, the largest you can print a
    shot is 4" by 3" (i.e. 1600/400 and 1200/400) without the picture
    beginning to look blocky. Note that you may not notice the blockiness
    until the print is substantially larger than 4" by 3".

    If your camera or the files you create has a different resolution, work
    out the equivalent sizes yourself.
    Best Regards,
    Alex.
     
    Alex Butcher, Jul 5, 2004
    #2
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  3. DS

    Jim Townsend Guest

    The dots of ink a printer squirts on paper and pixels in an
    image file have nothing to do with each other. The 'dots'
    in each case are completely different things.

    The accepted resolution for quality printing of an image file
    is 250-300 pixels per inch of paper. You don't gain much by going
    higher than 300 pixels per inch of paper.

    So.. If you wanted to print a 6" x 4" photo at 300 pixels per
    inch, your file would have to be 1600 pixels by 1200 pixels

    To determine the required number of pixels, just multiply

    300 pixels per inch X 6 inches of paper = 1600 pixels total
    300 pixels per inch X 4 inches of paper = 1200 pixels total

    If you don't have enough pixels in your image file, you can
    interpolate to 'make up' more.. Doing this does not add detail,
    it just prevents the image from becoming jaggy..
     
    Jim Townsend, Jul 5, 2004
    #3
  4. You seem to be getting some pretty bad advice here. You can do an
    experiment yourself to see how big you can print. Just keep enlarging
    your picture until you see some sort of degrading in the image. I think
    you'll find you can go a lot larger than 3 x 4 inches.

    Gary Eickmeier
     
    Gary Eickmeier, Jul 6, 2004
    #4
  5. DS

    Don Stauffer Guest

    In fact, to avoid confusion, I recommend not talking about the 'dots'
    per inch of the image file, referring to it as pixels per inch, ppi. As
    Jim says, pixels are not dots and vis versa.
     
    Don Stauffer, Jul 6, 2004
    #5
  6. DS

    Ron Guest

    Correction on Jim's math here. 300 X 6 = 1800 NOT 1600
     
    Ron, Jul 6, 2004
    #6
  7. DS

    Jim Townsend Guest

    LOL.. You got me. I was typing, but not thinking :)
     
    Jim Townsend, Jul 6, 2004
    #7

  8. You seem to be getting some pretty bad advice here. You can do an
    experiment yourself to see how big you can print. Just keep enlarging
    your picture until you see some sort of degrading in the image. I think
    you'll find you can go a lot larger than 3 x 4 inches.

    Gary Eickmeier
     
    Gary Eickmeier, Jul 6, 2004
    #8
  9. DS

    JPS Guest

    In message <pgoGc.24865$>,
    You need not waste paper and ink, either; you can take small critical
    sections of the images, copy and paste them as a new image, and even
    print multiple ones on a single sheet of paper, if you set the offsets
    right. It amazes me how many people never think of this, and waste a
    lot of paper and ink experimenting with printing.
    --
     
    JPS, Jul 6, 2004
    #9
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