RAW Files and DPI? (5D Mark III)

Discussion in 'Digital Photography' started by Mac In School, Jun 13, 2012.

  1. Mac In School macrumors 65816

    Joined:
    Jun 21, 2007
    #1
    I enjoy RAW files and feel I understand most of their benefits, but what I don't understand is, do they have a DPI, just like other raster-based image formats do? If so, does anyone know what the DPI is on the RAW file of a 5D Mark III?

    It seems like some cameras have high DPI / small dimensions, while others have low DPI / large dimensions. I could be wrong. I probably am.

    What I'm getting at, is I'm trying to figure out what DPI to specify in Aperture for my external editor DPI. If the RAW file is 72, I don't want to leave set it to 300 and unnecessarily bloat the file when I'm roundtripping it while editing.

    Thanks.
     
  2. Prodo123 macrumors 68020

    Prodo123

    Joined:
    Nov 18, 2010
    #2
    All images do not have a set DPI.
    DPI is only determined by the paper size that you use to print your photos on.
    If the Canon 5D Mark III (5760px across) prints a 3"x5" image, then the DPI will theoretically be 1152 (5760/5). However, when printed on a 12"x18", the same photo will be 320 DPI (5760/18).

    Do not depend on the DPI setting of Aperture's export format. Keep it at 300 and you will be fine. The image that exports from Aperture will still be of the same resolution anyway (5760x3840), regardless of the "set DPI."
     
  3. Mac In School thread starter macrumors 65816

    Joined:
    Jun 21, 2007
    #3
    Thanks for the reply. Just to be clear, we're talking about exporting to my external editor, not exporting for output. That stuff still applies, right?
     
  4. joemod macrumors regular

    Joined:
    Jun 8, 2010
    Location:
    Athens, Greece
    #4
    Yes. According to wikipedia "DPI is used to describe the resolution number of dots per inch in a digital print and the printing resolution of a hard copy print dot gain; the increase in the size of the halftone dots during printing. This is caused by the spreading of ink on the surface of the media." (source)
     
  5. Designer Dale macrumors 68040

    Designer Dale

    Joined:
    Mar 25, 2009
    Location:
    Folding space
    #5
    DPI dosen't really apply in the sense that the op is asking. A raw file is a digital negative and an analogy with film can be made here. Film is made up of grains of silver salts that react to light, so each grain could be considered a sensor element, a dot if you will. My 7D has an 18 MP sensor so it has about 18,000,000 light sensitive elements. Dots, if you will (again). This gives me files that are 4623 × 3082. If I print at 300 dpi the print is about 11x17. If I "print" for the web at 72dpi, the size becomes 48x72 (4 feet by 6 feet). If I keep messing with the Image Size settings in PhotoShop until the image size is about the same as the sensor size so that it is equal to a film negative, the pixels/inch is around 4000. So I could say my 7D has a dpi of 4000.

    The OP has more.

    Hope this muddies everything up...

    Dale
     

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