Advice needed for saving images to disc

Discussion in 'Photography Beginners' Forum' started by joeamy05, Apr 13, 2010.

  1. joeamy05

    joeamy05 TPF Noob!

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    I took some family portraits for a friend. I want to save them to a disc so she can then go and have the images printed at whatever printer she chooses. I have done this before and just saved the edited images as jpegs and then burned them to a disc, and it worked fine.
    However, I know one image in particular she wants to make a rather large print...and of course it is an image I have cropped in quite a bit. I have photoshop cs4, isn't there a way to increase the image size? Does that result in a huge loss of quality? How should I save these images for her to get the best image quality...and how will she (or the printer) know what is the max print size for each image?
     
  2. KmH

    KmH Helping photographers learn to fish Supporting Member

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    Yes you can resize the image in Photoshop.

    First the image needs to be in the correct aspect ratio.

    Most digital SLRs make images in the 3:2 aspect ratio. Put another way the long side of the image is 1.5x the short side.

    8 x 10's have a 5:4 aspect ratio so an image cropped to 3:2 won't work as an 8 x 10 but will as an 8 x 12.

    Pixel dimension and resolution determine how big a image can be printed

    If an image is 3000 pixels by 2000 pixels (3:2 aspect ratio) and it has a resolution of 300 ppi (pixels per inch) it can be printed 10 inches wide (3000/300 = 10) and 6.67 inches high (2000/300 = 6.67)

    That same 3000 pixel x 2000 pixel image printed at a resolution of 100 ppi can be printed 30 inches wide (3000/100 = 30) and 20 inches high (2000/100 = 20).

    It's all just 5th grade math.
     
  3. joeamy05

    joeamy05 TPF Noob!

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    At what resolution (ppi) do you start to lose image quality? ..and thanks for the help...now I need to go ask my 5th grader to do some math for me..ha
     
  4. vtf

    vtf No longer a newbie, moving up!

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    I new I shouldve studied harder!:lol:
     
  5. KmH

    KmH Helping photographers learn to fish Supporting Member

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    It varies by image.
    One of the most popular online consumer print labs is Mpix.com. They will not accept (stake their reputation on) prints made from image files at a resolution of less than 100 ppi.

    If you upload a file that is 99 ppi, they won't print it.

    So, that would be the minimum I would recommend.

    Here is a link to Mpix's "How To Prepare Images" support page:
    Mpix.com - Help
     
  6. aliciaqw

    aliciaqw TPF Noob!

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    What's the difference between DPI and PPI?
     
  7. Big Mike

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

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    DPI - Dots Per Inch - is a printer function. It's the number of dots of ink that are printed onto the paper.

    PPI - Pixels Per Inch - is a number that tells the computer how large an image should be displayed on a monitor.

    They are often used interchangeably, and that is wrong. DPI should be left up to the printer, no need to think about it. PPI doesn't really matter either.
    The important number to know, is the size of the image...in pixels.

    For example, if you have a file that is 2000x3000 pixels, you can set the PPI to 300 and it will look very large on a computer screen (or you will be viewing it at 25% zoom etc. You can change the PPI to 72 (without re-sampling) and it will only change the size on the screen. If it's still 2000x3000 pixels (in actual size) you haven't lost any quality.

    Now, when it comes to printing...you do need enough resolution/information and this is also PPI....but in this case, it's pixels per inch of print. As mentioned, you don't want to go lower than 100, but 300 is a typical standard that people use for high quality photo images.
    If your image is set to a lower PPI, you can change it to a higher number, but that won't necessarily increase your image size. In Photoshop, you can check a button to 're-sample' when you change the PPI, and thus increase the actual size (number of pixels)...but when you do this, Photoshop has to make up the new pixels, and thus the quality will drop.

    So remember, the most important number to know, is the actual size of the image (in pixels). You can use that number to decide how large of a print you think you can make.
     
  8. Boomn4x4

    Boomn4x4 TPF Noob!

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    Jooeamy.... All of your questions can be answered if you post the ppi of the image, and its images size in pixels (ie 1944x2592)
     
  9. joeamy05

    joeamy05 TPF Noob!

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    2259x3153... Thanks again
     
  10. Boomn4x4

    Boomn4x4 TPF Noob!

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    If the image is 100 pixels per inch (ppi);

    2259/100 = 22.6"
    3153/100 = 31.5"

    so you can make up to a 22.6" x 31.5" print without loss of image quality.

    If the image is 300 ppi

    2259/300 = 7.5"
    3153/300 = 10.5"

    so you can make up to a 7.5" x 10.5" print without loss of image quality.
     
  11. KmH

    KmH Helping photographers learn to fish Supporting Member

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    How large an image is displayed on a monitor is only governed by the monitor's resolution setting and the image's pixel dimensions.

    PPI only has meaning when an image will be printed.
     

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