Resolution

Discussion in 'Photography Beginners' Forum' started by Trentlee07, Oct 9, 2007.

  1. Trentlee07

    Trentlee07 TPF Noob!

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    Ok I am new to photography. I work for a mail order company and design the annual catalog and maintain the website. We are taking all of our own photos for our catalog. My problem is that when i put the photo i have taken on my computer the resoultion is only 72 DPI. is there a way to get it to come over at higher DPI? My question is very amature i am sure but i would appreciate your help. Thanks in advance..
     
  2. Big Mike

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

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    Welcome to the forum.

    The resolution is set at 72 PPI (Pixels Per Inch) because that is sufficient for monitor display. That number really isn't important though. The important number is the actual size of the image, in pixels.
     
  3. Sideburns

    Sideburns TPF Noob!

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    It's usually pretty important for printing...when you put it on a layout page, if it's too low it shows up poo...You can always change it though when you do the final layout.
     
  4. Big Mike

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

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    I'm talking about the PPI...which is actually what the OP was asking about (whether they knew it or not). And it isn't' important. You could change it to 12 or 12,000 (without re sampling) and it wouldn't change the image one bit (except for how large your monitor wants to display it).

    If the image is 3504 x 2336 (pixels)....that is what is important.

    Now when you switch from talking about a digital image on the screen...to an image that will be printed...then you will want to consider the number of pixels per inch (of print). Most people will say that 300 is the number to use....so for an 8x10 print, you would want an image file that is at least 2400 x 3000 pixels.

    DPI (dots per inch) is a printer setting/function for how many dots of ink that are laid down onto the paper...and this doesn't necessarily have anything to do with the number of pixels in the image.
     
  5. Digital Matt

    Digital Matt alter ego: Analog Matt

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    Embedded ppi / dpi in a jpg is meaningless. The print size is determined by the pixel resolution of the file divided by DPI setting of the printer. The embedded resolution number only becomes meaningful if you want to resize your file to a certain print size, or if the printer itself demands that the PPI be set to a certain size. For posting on the web, it is certainly meaningless.
     
  6. Helen B

    Helen B TPF Noob!

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    Trentlee,

    What software are you using? You should be able to set the image ppi and/or image size somewhere in the software. For example in Photoshop you would select 'Image' on the menu bar, then 'Image Size'. There you can set the ppi and image size you want, with or without resampling. In most cases that is what determines the print size, not the dpi setting of the printer.

    As Big Mike says, the ppi set in the image file is unrelated to the dpi setting in the printer driver. For example you can print a 300 ppi file at 1440 dpi or at 760 dpi, and the print will be 300 ppi in both cases - ie exactly the same size.

    All the above is in reference to print output.

    Best,
    Helen
     
  7. Alex_B

    Alex_B No longer a newbie, moving up!

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    I think we should place this statement somewhere visible on this forum.

    maybe we need a tutorial on resolution to which we can refer whenever the question emerges? After all this dpi / ppi / pixel / inches confusion is something which really confuses 80% of all beginners!
     
  8. Helen B

    Helen B TPF Noob!

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    But it isn't meaningless when you print, or more importantly, when you send files to be printed.
     
  9. Digital Matt

    Digital Matt alter ego: Analog Matt

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    99% of the time, it is actually. The DPI of the printer trumps any embedded PPI.
    Since print resolution is a factor of Pixel Resolution / DPI, what you have embedded in the file (PPI) is really meaningless. It is there so when you are resizing an image, you don't have to calculate the math in your head. If your intended output is 4x6 @ 300 DPI, you would change your PPI to 300 in order to determine the pixel resolution you need in your file. Photoshop, or whatever program you are using then knows to resize the image to 1200 x 1800 pixels.

    The only instance I have seen where this is different is a small dye-sub printer we have at work, which takes into account the PPI embedded into the file. Most photo printers print at the DPI they are set to regardless. I've seen many cds of jpgs sized to 1200x1800 at 72 DPI sent to the lab, and the prints came back as 4x6s.

    Now, just to clarify, when I'm sending my files to be printed, they are sized accordingly and the PPI is set to 300, not because it needs to be, but because it is part of my workflow when resizing pictures for print, as it makes it easier to visualize the intended outcome.
     
  10. Helen B

    Helen B TPF Noob!

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    If you send a file to an online printing service, how do they know what size to print, if you don't ask for it to be sized to fit the paper, and if they don't specify 300 ppi and always print at 300 ppi? Only by setting the print size and ppi in the file itself. Some labs print at 300 ppi (and 300 dpi, if it is an LED or laser printer such as a Chromira or Lambda) no matter what the ppi embedded in the file is, but some labs do print at the embedded ppi. Ezprints is one such lab (and excellent they are, by the way).

    When I send a file to one of my printers (three 2200s, one R2400, one R800, one 3800), how do I set the print size? By setting the print size in the file. The dpi of the printer has absolutely nothing to do with the print size. Send an 8x10, 300 ppi jpg file to a printer and it will print at 8x10, no matter what the printer dpi is set to. There may be an option to adjust the print size in the printer driver, which complicates the issue.

    One of the things that resizing to the output ppi or dpi (if dpi is appropriate) does is to determine which piece of software does the interpolation, and then the sharpening. Edit for clarification (? maybe!): this is only the relationship between the pixel dimensions of the file and the ppi it is printed at, it is not necessarily a function of the embedded ppi, but embedding the optimum ppi is the easiest way of fixing the relationship. Finding the optimum ppi for your printer can be a worthwhile exercise - as an example, for the 2200 it is 288 ppi in some instances.

    Print resolution is not pixel resolution / dpi if the printer dpi is higher than the file ppi.

    As a blanket statement it is not true to say that the ppi embedded in a jpg is meaningless - it needs to be qualified.

    Best,
    Helen
     
  11. Big Mike

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

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    Any on-line printing service that I have used, asks for the print size, somewhere in the ordering process.
     
  12. Helen B

    Helen B TPF Noob!

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    Isn't it more accurate to say that they all ask for the paper size, not the image size? I should have written "If you send a file to an online printing service, how do they know what size to make the image,..." to make my point slightly clearer. Perhaps. Or maybe not. Well, I know what I mean.

    Best,
    Helen
     

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