dpi Question

Discussion in 'Film Discussion and Q & A' started by pixie09, Nov 16, 2009.

  1. pixie09

    pixie09 TPF Noob!

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    I took my 35 mm film in to be developed, ordering 4x6 prints & a cd. I then downloaded the pictures from the cd to my computer. When opened one of the tifs up in Photoshop CS4 and went to "image size" it came out as the following:

    width: 25 in
    Height: 16.875
    Resolution: 72


    Why are they coming out this way, as opposed to 300 dpi in 4x6 size?

    Thanks in advance for any clues!
     
  2. lbridges

    lbridges TPF Noob!

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    If you change just the DPI in CS4, the image size will drop down to something like you were expecting. I suspect (but haven't actually checked) the 72 DPI is some sort of Photoshop default - it will not adversely affect your photo - reiterating - change just the DPI to 300, and watch the image size change,
     
  3. pixie09

    pixie09 TPF Noob!

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    Thank you very much! I will give that a try.

    Have a great day!!
     
  4. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    It's not DPI (dots per inch)...it's PPI (pixels per inch) and it doesn't mean anything. It's just telling the computer how large to display the image on a computer screen.
    72 PPI is the typical resolution of a computer monitor...which is why it's often the default setting for digital images.

    In the 'Image Size' box, you can simply change it.
    First, uncheck the 'resample image' box...then change the PPI to 300 (or whatever)....then recheck the 'resample Image' box. You image will now have a different PPI...but will otherwise be exactly the same.
    The 'document size' will change...but that's just how large it is (at 100% zoom) on your computer screen. The actual pixel dimensions won't change.
     
  5. apertureman

    apertureman TPF Noob!

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    Just make sure you have "Resample Image" check box UNCHECKED when you change the image resolution.

    25" at 72 dpi = 6" at 300 dpi
    16.875" at 72 dpi = 4.05" at 300 dpi


    You're still good.

    There's no need to recheck the box, just hit OK.
     
    Last edited: Nov 16, 2009
  6. Dwig

    Dwig TPF Noob!

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    Correct. PS will default to 72ppi when it encounters a file that has no PPI value set in its header. This is the common choice from most apps that deal with PPI. You would have to read through the EXIF data in the header to see whether the lab's software specified 72ppi (which I doubt) or whether it left the field blank.
     

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