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Thread: DPI Question

  1. #1
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    DPI Question

    Hey guys , i need help with a question.

    I have a 600 DPi image that i want blown up, how big can i get it printed? So that it looks good.

    Thanks


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    DPI = dots per inch (i assume you actually mean pixels per inch, btw). how big is the image in inches when spec'd at 600 dpi? do you have the pixel dimensions? (pixels wide x pixels deep)

    if you just want a % enlargement factor, you need to know what halftone dot screen ruling your work will be printed at. generally that's around 150 LS (line screen), but can vary a great deal depending on the print vendor. a lower screen ruling will allow more enlargment but yield lower quality results in the printing.
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    The original size is Width - 4.115
    Height - 6.078 at 600 DPI

    I just want a rough estimate as to how big it can be blown up, without being obscured.

    Thanks

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    I believe he means DPI (which is what the image will actually print at, PPI is a measure of screen resolution).

    If you are using Photoshop go to the Image Menu and open the Image Size menu box. Now uncheck the the option at the bottom of that panel marked
    Resample Image. This should link the width, heighth & resolution of the image. Now change the resolution to 300 dpi. This should automatically change the width & heighth of the image, showing you how big it will actually be. Now 300 dpi is the standard print resolution for quality printing, you can go as low as 250 with minimal issues, but I wouldn't recomment it for portfolio work.

    Hope that helps!

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    offset print goes with roughly 300 dpi (304 i think) for stuff you hold in your hands or view very close. artprints aswell.

    in generall its best to ask the printer that will do the job on how to prepare your data for printing. (like color profiles, resolution, etc).

    if youre just printing it on a laser printer you can go as low as 200 dpi... maybe 150 but only if you have to. (depends on the printer aswell).
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    "how big it can be blown up, without being obscured" is really dependant on a number of factors, not the least of which is what you mean by "obscured." in general, for offset print, the minimum medium-quality halftone screen ruling is 133 LS. for better to best full color work, 150 LS to 200 LS is recommended. you'll have to talk to your printer about what's available; some presses can't run the finer (higher number) screens and maintain quality. this is assuming you're using offset printing. if not, you'll have to specify the type of reproduction, since there are widely varying requirements.

    the other factor is what DPI/LS ratio you use. 2 is a common standard, but as low as 1.5 can also be used, so:

    minimum line screen = 133, DPI/LS ratio = 1.5
    1.5 x 133 = 199.5 or approx 200 dpi minimum effective resolution.
    since you have
    600 x 4.115 = 2469 pixels wide by
    600 x 6.078 = 3647 pixels deep
    (check your file and see if the pixel dimensions match these calcs, btw)

    at 200dpi, your file would be 12.345" x 18.235" deep (3x the size it is now). you can go larger than this but by usual standards your image will start to degrade.

    for offset printing at 150 line screen, with effective pixel resolution of 300 dpi, that would be 8.23" x 12.156" if using the common standard DPI/LS ratio of 2, basically twice the size of what you've described.
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    Quote Originally Posted by CRW
    I believe he means DPI (which is what the image will actually print at, PPI is a measure of screen resolution).
    the image will actually print in halftone dots if being printed by offset, usually at around 150 dots per inch, usually spec'd as 150LS (150 line screen). wanted to be clear we we're talking about pixels, not halftone dots, when speaking about the 600DPI (dots per inch) spec.

    clear as mud, huh?
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    I . Miss . America -- "colored [eyes] may hypnotize..."

    "In the end, Razputin, aren't we all just dogs playing poker?"
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    Quote Originally Posted by masque
    the image will actually print in halftone dots if being printed by offset, usually at around 150 dots per inch, usually spec'd as 150LS (150 line screen). wanted to be clear we we're talking about pixels, not halftone dots, when speaking about the 600DPI (dots per inch) spec.
    clear as mud, huh?
    Masque,

    I think a clearer explanation of dpi as opposed to ppi would be thus:

    dpi or line screen (lpi): These are the color or B/W dots you would see if you were to look at a magazine or newspaper through a lupe or magnifying glass. The dots are actually in lines or rows and are usually measured by how many lines of dots fit inside a square inch. This number has nothing to do with how many pixels are in the image though a ppi number that is too low will affect image quality. The printer (the print shop, not the device connected to your computer) sets this number based on where the image will be published.

    ppi or pixels per inch: this is your actual image density. The most common formula used to determine the best quality for professional printing is: an image at the actual size it will be used should have double the ppi of whatever lpi it will print at. The most common lpi for newspaper reproduction is 85 lpi, trade magazine is 133 lpi and high concept mags like architectural digest print a 150 lpi or higher. If you know where the image will be published, it's easy to guess what ppi to create the image at or what scan settings to use. This is by no means the only formula that is used, it's just the most common one I have run into.
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    good words, figure2. i just wanted to be brief, but i guess it's a subject brevity can make unclear for those not used to juggling all the terminology. thanks!
    Continuity Break -- my sketchbook

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    ArmaRagnaGeddonRock-yer-Yuga! -- celeztial shitz 'n' gigglez
    I . Miss . America -- "colored [eyes] may hypnotize..."

    "In the end, Razputin, aren't we all just dogs playing poker?"
    -- Edgar Teglee

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    Thanks for all the info guys, the idea is (I should have mentioned it originally)
    to blow up some comic pages to a small poster size for b-day party for a friend.

    Around 20" x 26"

    Just wanted to make sure it could go that size at the current resolution.

  12. #11
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    Quote Originally Posted by Lone Wolf
    Thanks for all the info guys, the idea is (I should have mentioned it originally)
    to blow up some comic pages to a small poster size for b-day party for a friend.
    Around 20" x 26"

    Just wanted to make sure it could go that size at the current resolution.
    Assuming you don't resample the image when you enlarge it, the comic page will end up at around 140 ppi. Posters are meant to be viewed from a distance so it will probably be OK.
    Mark Hannon
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