Dots or pixels per inch

Discussion in 'General Mac Discussion' started by MoonShadow, Apr 6, 2004.

  1. MoonShadow macrumors newbie

    Joined:
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    Idaho and Baja
    #1
    I'm trying to send a photo to a magazine and they call for a size of 8" X 10" and 300 dots per inch. When I go to image/size (in photo shop) and then select 8 X 10 inches for the size. My only choice is pixels (not inches) and when I select 300 pixels per inch my photo comes out way to large. Any ideas ?

    Thanks,

    MoonShadow
     
  2. jayscheuerle macrumors 68020

    jayscheuerle

    #2
    That's what they want. A large picture. 24 megs or so. But it won't do you any good to increase the resolution. An image has to have that resolution right off the bat for it to be clear as possible.

    Good luck. - j
     
  3. PixelFactory macrumors regular

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    Chicago
    #3
    They do mean pixel per inch. So at 8"x10" your pixels should be at 2400x3000. The image looks large on your screen because your screen displays images at about 72 pixels per inch.
     
  4. Bear macrumors G3

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    Sol III - Terra
    #4
    Pixels=Dots in this case.

    They want the image o be set 300DPI/PPI and 2400 by 3000 pixels.

    They want you to do the work of upsizing it for their printing process. This however does give you more control of what process is used to enlarge the image.
     
  5. MoonShadow thread starter macrumors newbie

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  6. MisterMe macrumors G4

    MisterMe

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    #6
    That's not quite right. They don't want MoonShadow to increase the resolution of his image to 2400 x 3000. Its original resolution has to be at least 2400 x 3000. If it is greater than 2400 x 3000, then it can be downsampled. Digitally upsizing an image, however, will not increase the number of its useful pixels. Upsizing will only create a large files with the same useful resolution.
     
  7. Bear macrumors G3

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    #7
    You can get that resolution from a slide/negative scanner and from only a couple of digital cameras. After that, you need to upsample the picture and since there are many methods to do so, making the photographer do it is probably best. Also, this way the photographer gets to choose how to crop the image since 8 by 10 is not a standard aspect ratio for any camera I know of.
     
  8. MisterMe macrumors G4

    MisterMe

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    #8
    You are correct in that you can only get 2400 x 3000 resolution using a scanner or a few digital cameras. The scanner need not be a slide or negative scanner because you can also scan a print. After all, that's what drum scanners do. However, the publisher is perfectly capable of upsampling digital images if it served a useful purpose. It does not.
     
  9. zim macrumors 65816

    zim

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    Jan 5, 2002
    #9
    They are incorrect in their wording, a mistake that has been made by many for years past and most likely years to come. All digital imagery is measured as ppi, pixels per inch, not dpi or dots per inch. dpi refers to the screen resolution or even an ink jet printer but not a digital image.
     
  10. Sparky's macrumors 6502a

    Sparky's

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    Feb 11, 2004
    #10
    As a graphics professional and being involved with commercial printing for over 30 years I see a lot of misquoted facts concerning resolution vs. lpi vs. dpi and ppi.
    dpi = dots per inch (also lines per inch, lpi) as physically printed on paper.
    ppi = pixels per inch, the actual number of pixels contained in the photo.

    I have always followed this rule of thumb: continuous tone images (grayscale, CMYK, duo-tone etc.) should be twice the resolution (300ppi) of the printed output (150lpi)
    Line art or bitmapped images should be the highest resolution possible to match the output device, i.e. an imagesetter that RIPs at 2400 dpi should have the artwork scanned to 2400 dpi.

    I have no affiliation with this company but I found this page of theirs to be extremely helpful and informative.

    http://www.printwatkins.com/support/formula01.shtml
     
  11. Nny macrumors regular

    Nny

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    Apr 7, 2004
    #11
    Kinkoid in the Forum

    Well, that can be a misquoted fact right there. Your phrasing implies that DPI=LPI in a 1:1 ratio, which is not correct. LPI & DPI are not the same value because they do not measure the same things. DPI determines the size of dots an output device will use when printing (a 300 DPI printer will print dots that are 1/300th of an inch). LPI (lines per an inch) determines spacing of halftone dots, which therefore determines maximum size of the dots. Their values are quite different: a 600 dpi printer is 106 lpi, for example.

    And I'm not a graphics pro... just a guy working at a Kinko's.
     
  12. Nny macrumors regular

    Nny

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    Apr 7, 2004
    #12
    And another thought...

    That's the rule I was always taught... your mileage may vary though. The higher the multiplier you go the smoother the result. If you want it crisp go with a lower multiplier (1.5x usually is crisper looking). Big exception to this rule is high contrast lines. Go to at least 2.5x the LPI to avoid the jaggies.
     
  13. primalman macrumors 6502a

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    #13
    I wanna chime in here, just so we are all clear.

    PPI is pixels per inch, which is how resolution in a digital realm is measured, such as the resolution of a digital image or a dispay screen.

    DPI is dots per inch, which are device measurments, such as the way a laser printer, inkjet or imagesetter produces the teeeny-tiny induvidual parts of a printed image. Or as a scanner sees each samll portion of an image to create the final image, it is seeing more than is recorded in the final image, so a 300 ppi image is seen though the eyes of 2400 dpi.

    The comsumer scanner and printer makers have jacked up this and other terminolgy over the years ina way that is nearly irreparable. Ugh.
     
  14. Sparky's macrumors 6502a

    Sparky's

    Joined:
    Feb 11, 2004
    #14
    As previously stated dpi and lpi do represent basically the same thing, [units per inch] where lpi does refer to grayscale "lines of dots" per inch and dpi are the number of "dots per inch" for bitmapped images, its the same reference, and in commercial printing often used to mean the same thing.
    Maybe reading this will help a little more.
    http://graphicdesign.about.com/library/weekly/aa070998.htm
     

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