JPG at 72 dpi

Discussion in 'Photography Beginners' Forum' started by MACollum, Jul 26, 2007.

  1. MACollum

    MACollum TPF Noob!

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    I'm preparing some photos for entry in the OK State Fair this fall and came across some pictures I took in JPG large format in the first month or so after I got my DSLR. I might want to enter one or two but I'm not sure what to do since they came out of the camera at 72 dpi.

    In Photoshop (under image size, pixel dimensions) it says that the width is 3888, height is 2592. The document size says width 54 inches, height 36 inches, 72 pixels/inch.

    Do I just need to change the resolution to 300 ppi and keep the Resample Image box UNchecked? On the screen the image doesn't seem to change but the image size changes to a normal print size (roughly 12 x 8 inches), which I will then resize to 8 x 10 (if I'm right). Thanks!
     
  2. Alex_B

    Alex_B No longer a newbie, moving up!

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    The dpi- or ppi-value saved with some digital files does not matter at all. 72 ppi or dpi at 36 inches is the same as 144 ppi at 18 inches and it all does not matter for the file since all which counts are the pixels. just keep all of them (in other words do not downsample.)

    300 dpi for printing is only a guideline ... if you supply images which do only 200 dpi or even 400 dpi for a given size, then they will still look great.
     
  3. MACollum

    MACollum TPF Noob!

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    I thought so...I feel like an idiot now. I'd always heard that it didn't matter but then there was the thing about wanting 300 for printing and I just wasn't too sure anymore. I'm going to be getting SOOOO many prints made and I'm so broke now it's not funny. I've got to enter the pictures by about the middle of Aug, so I can't afford to get it wrong. Thanks again!
     
  4. ANDS!

    ANDS! No longer a newbie, moving up!

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    DPI and PPI arent the same though and refer to two different things. Generally speaking (from what I understand) you want your DPI to be larger than your PPI. As for PPI 200-300 is a safe range for good looking pictures. 72PPI is fine for prints, but stretching that image out doesn't produce as good an image as one that has more pixels slotted into the same area, for example a 300PPI image.
     
  5. Alex_B

    Alex_B No longer a newbie, moving up!

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    Strictly speaking this is true! But most software mixes this up terribly. Many programmers apparently did not know about printing and terminology.
     
  6. EOS_JD

    EOS_JD TPF Noob!

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    Images are made up of pixels so the correct term when discussing resolution for a digital image is ppi (pixels per inch).

    dpi is dots per inch and refers to either a scanning resolution of your scanner or your printers output in dots per inch


    Generally speaking all of todays printers print at way higher than 300dpi. My R2400 can print at 5760 dpi x 1440 dpi.

    Correction - 200-300ppi is a safe range for good looking PRINTS.

    72ppi is nowhere near enough for a decent print (unless that print is rather large and you have enough pixels to make it). For small images, you need those pixels packed together so 200-300ppi is required. For larger images, because you view them from a greater distance, you can get away with a lower resolution although I don't think I'd ever print anything at 72ppi!
     
  7. EOS_JD

    EOS_JD TPF Noob!

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    Yes Alex this is terribly confusing for some. So long as people are aware of the differences that's all that matters. Printers print in dots, scanners scan dots and images are made up of pixels.
     
  8. Alex_B

    Alex_B No longer a newbie, moving up!

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    Hmm, but then again the scanner creates pixels ... not even the original you scan contains any dots (unless it is a print).

    That is because you never print really large i suppose. If something is going to hang in front of a building, then you will be fine even with much less than 72ppi ;)

    I have seen a 10 x 10 metre print which only had about 4 dpi or so, and it did look stunning.
     
  9. EOS_JD

    EOS_JD TPF Noob!

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    Close Alex. The output of a scanner is a digital image that is rightly measured in ppi however a scanner is an input device and scans in dots per inch. As you note final image is then digital and is measured in ppi.

    The original scanning print or sheet is scanned by the print head and you control the resolution in dpi.

    i agree with this alex. If you note I did qualify my words.

    You are correct I don't print that big usually but I am aware that large banners are printed at very low resolutions. My normal size is 19"x13" (A3+) at 180ppi and these look amazing.
     
  10. Alex_B

    Alex_B No longer a newbie, moving up!

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    I know, just wanted to add my comment as well ;)
     
  11. Alex_B

    Alex_B No longer a newbie, moving up!

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    we are splitting hairs now, ... but it is fun :)
     
  12. EOS_JD

    EOS_JD TPF Noob!

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    Just to split more hairs, here's a description of what the scanner does. http://www.scantips.com/chap3c.html:D
     

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