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Thread: dpi to pixels

  1. #1
    SitePoint Guru cyjetsu's Avatar
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    dpi to pixels

    When someone asks for a graphic in a size of dpi, say 300 dpi, how many pixels do they want?

  2. #2
    Follow Me On Twitter: @djg gold trophysilver trophybronze trophy Dan Grossman's Avatar
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    That depends on how many inches they want.

    A 2" by 2" square at 300 dpi is 360000 pixels (2 inches * 300 pixels = 600 pixels long and 600 pixels wide, 600*600 = 360000 total pixels).

    People usually ask for something in a certain DPI because they intend to print it. If you give them a 72dpi image which is what most stuff displayed on a computer monitor is, it's not going to look well when printed at a reasonable size. Knowing that the graphic is for print should help you guesstimate a good physical size if they didn't provide one.

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    Programming Since 1978 silver trophybronze trophy felgall's Avatar
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    That all depends on how many pixels they have their monitor set to display per inch which in turn depends on their screen size and resolution. There is no one to one between dpi and pixels.
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    Night Elf silver trophybronze trophy Varelse's Avatar
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    I agree with Dan Grossman - "300 dpi" is a key word used by clients when the graphics is to be printed. However with no physical size (cm/in) given, this information is worthless.
    If you provide the image - let's say - 100x100px in size, it does not have any dpi resolution. Resolution only comes into play when you are going to reproduce the image at a certain device with its resolution - either print or display.
    So for that 100x100px image, saying that it is a 300 dpi one is not true (you can say it's 10dpi or 2000dpi as well), but if you say that's 1/3 by 1/3 inch large at 300 dpi, then you are right.
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    SitePoint Guru cyjetsu's Avatar
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    Thanks. I had a feeling the dpi on its own was worthless but then I thought I might be missing something that everyone else knew and would check anyway. The client was asking for a logo. Would it not be best to just give the logo in vector format so they can make it any size they want anyway.... is it me or does the client not know much about graphics?

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    Follow Me On Twitter: @djg gold trophysilver trophybronze trophy Dan Grossman's Avatar
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    That's probably the case, and you should give them the logo in vector format and rasterize it in a few common formats/sizes as well. They may not have the software to open the vector file, but might need it to pass on to another designer in the future.

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    SitePoint Guru cyjetsu's Avatar
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    Thanks for the info. I will also remember to ask them what size they intend to print it at.


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