JPG Image Size & Internet

Discussion in 'Digital Photography' started by Rhobes, Jun 27, 2013.

  1. Rhobes, Jun 27, 2013
    Last edited: Jun 27, 2013

    Rhobes macrumors 6502


    Oct 28, 2004
    Bigfork, MT
    Hi All-

    I can't recall where but I heard or read that resizing eg a 300ppi file to 72ppi for net use is not necessary anymore, but I don't remember the reason why. Can anyone tell me if that is true to a certain extent and why?

    I can say for myself that the two (a 300ppi file & a 72ppi file) will download at the same rate on my system. But, I know there are times it may not download a large jpg as fast as other times, yet infrequently.

    I know your sending more file then the monitor uses but if a 300 vs a 72ppi pic opens at equal speed is there reason to re-size images every time you send one?

    I have been told, "lets not pollute the Internet with large ,jpg files that are meant for hi-res Printers. More detail is just a waste of bandwidth." Is that a true statement? Is sending eg. a 240ppi pic to someone misuse of the internet? polluting it?

    Thanks for your comments.
  2. Laird Knox macrumors 68000

    Jun 18, 2010
    PPI, DPI and LPI do not have any impact on your files size. If your image is 2000 x 3000 pixels then it is 2000 x 3000 pixels at 72, 300 or 44,000 PPI. If you ask a browser to display it it will be 3000 pixels wide.

    Depending on the use and web site I typically constrain my images to between 400 and 800 pixels wide. Yeah, but at what DPI? I don't know. I never pay attention to that as it doesn't impact the display.

    Note: The new retina displays may change this slightly. I have not worked with one yet and am not sure of the ramifications.
  3. ChrisA macrumors G4

    Jan 5, 2006
    Redondo Beach, California
    You heard right. the PPI setting is almost universally ignored. and all it is, is just a one number in the file header someplace. For photos headed to the web it is a useless setting.

    All that matters is the total number of pixels and the "quality" setting. The amount of compression makes a huge difference in size of the file and is controlled by the "quality" setting when you save the jpg file.

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