Re: Tutorial how to use Irfanview 4.25 to rotate, shrink, & rename batch photos

Discussion in 'Digital Photography' started by Tim, Apr 6, 2010.

  1. Tim

    Tim Guest

    Elmo wrote:

    > Assumption: You want to automatically rotate, shrink to 100KB, set to
    > 72dpi, strip out the EXIF data, and rename the new emailable files
    > based on the EXIF date & EXIF gps coordinates for all photographs in
    > a Windows folder.


    Why are you setting the resolution to 72 pixels per inch? If they are to be
    emailed and viewed on screen the resolution doesn't matter at all, if they
    are to be printed then 72 ppi is way too low.
    Despite the common misconception, on screen images don't need to have a
    resolution of 72 ppi. The only thing that effects its size and quality on
    screen is its size in pixels. The size can be changed if it's incorporated
    into a web page by a scaling factor, but it's best to make a copy that is
    the correct size (in pixels) to start with, and in either case resolution is
    irrelevant. For on screen images, the resolution only comes in to play when
    the image is displayed in a page based format, like Word or a desktop
    publishing program, where the software makes an inaccurate attempt to show
    the virtual piece of paper at the same physical size as it is in the real
    world.

    --
    Tim
    Tim, Apr 6, 2010
    #1
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  2. Tim

    Ray Fischer Guest

    Tim <> wrote:
    >Elmo wrote:


    >> Assumption: You want to automatically rotate, shrink to 100KB, set to
    >> 72dpi, strip out the EXIF data, and rename the new emailable files
    >> based on the EXIF date & EXIF gps coordinates for all photographs in
    >> a Windows folder.

    >
    >Why are you setting the resolution to 72 pixels per inch? If they are to be
    >emailed and viewed on screen the resolution doesn't matter at all, if they
    >are to be printed then 72 ppi is way too low.


    Does _anything_ pay attention to the DPI setting?

    --
    Ray Fischer
    Ray Fischer, Apr 6, 2010
    #2
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  3. Tim

    Tim Guest

    Elmo wrote:
    > On Tue, 6 Apr 2010 11:02:22 +1000, Tim wrote:
    >
    >>> Assumption: You want to automatically rotate, shrink to 100KB, set
    >>> to 72dpi, strip out the EXIF data, and rename the new emailable
    >>> files

    >> Why are you setting the resolution to 72 pixels per inch? If they
    >> are to be emailed and viewed on screen the resolution doesn't matter
    >> at all

    >
    > Good question!
    >
    > I thought reducing the DPI from whatever it is from the camera down
    > to 72 DPI lowered the file size (in bytes on disk).
    >
    > Can you clarify the relationship of DPI with bytes on disk?
    >
    > Assuming two photographs are exactly the same, except one is 72 DPI
    > and the other is, say, 1,200 DPI, wouldn't one would be vastly larger
    > in file size (bytes on disk) than the other?
    >
    > If the answer is Yes, then that's why I recommend 72DPI for emailed
    > photos. If the answer is No, then ... you're right ... it's a waste
    > of time to set the DPI in Irfanview Batch Mode.
    >
    > What is the right answer to recommend to batch shrink common photos
    > to be emailed?


    There will be absolutely no difference in file size. The only difference
    will be a few bytes in the file header that read will 72 in one image and
    1200 in the other. The part of the image that contains the image
    information will be identical.
    As an example, here are two images. Both are 800 x 600 pixel JPGs that were
    saved with the same settings for compression, but one has a resolution of 72
    ppi and the other is 1200 ppi. Both have a file size of 95,277 bytes.
    http://www.fileden.com/files/2008/6/28/1979560/Res72.jpg
    http://www.fileden.com/files/2008/6/28/1979560/Res1200.jpg

    Resolution is only applicable to printed images, or applications that show
    your image on a virtual piece of paper. Something like a word processor, a
    desktop publishing application or something with "print preview". This
    doesn't apply to web browsers, email programs, image viewers or image
    editors (in their normal mode).
    If you have an image that is 3600 x 2400 pixels and it has a resolution of
    1200 pixels per inch, it will print at a size of 3 inches by 2 inches. If
    you change the resolution to 600 pixels per inch it will print at a size of
    6 inches by 4 inches. That's all resolution means... a conversion factor
    from "pixels", which have no fixed size, to a physical measurement such as
    inches. It doesn't mean that each pixel contains more information at higher
    resolution. A pixel just contains the colour of one dot. Resolution doesn't
    mean the same as the resolving power of a lens.
    A good page about all of this is http://www.scantips.com/no72dpi.html

    --
    Tim
    Tim, Apr 6, 2010
    #3
  4. Tim

    Paul Furman Guest

    Re: Tutorial how to use Irfanview 4.25 to rotate, shrink, & renamebatch photos

    Tim wrote:
    > Elmo wrote:
    >> Tim wrote:
    >>
    >>> Why are you setting the resolution to 72 pixels per inch? If they
    >>> are to be emailed and viewed on screen the resolution doesn't matter
    >>> at all

    >>
    >> What is the right answer to recommend to batch shrink common photos
    >> to be emailed?

    >
    > Resolution is only applicable to printed images, or applications that show
    > your image on a virtual piece of paper. Something like a word processor, a
    > desktop publishing application or something with "print preview".


    Setting 72 ppi could be useful if people want to print a low res web
    image; that'll cause it to print by default at a size similar to what
    you see on screen, where a 300 ppi setting would come out of the printer
    at postage stamp size, but it has no effect on file size on disk.


    --
    Paul Furman
    www.edgehill.net
    www.baynatives.com

    all google groups messages filtered due to spam
    Paul Furman, Apr 6, 2010
    #4
  5. Tim

    me Guest

    On Tue, 06 Apr 2010 08:35:37 -0700, Paul Furman <>
    wrote:

    >Setting 72 ppi could be useful if people want to print a low res web
    >image; that'll cause it to print by default at a size similar to what
    >you see on screen, where a 300 ppi setting would come out of the printer
    >at postage stamp size, but it has no effect on file size on disk.


    That implies a fair amount of assumption about the
    application/feature/driver set up used to print he photo, doesn't it?

    html browser vs image viewer vs image editor vs image printing app.
    me, Apr 6, 2010
    #5
  6. Tim

    Paul Furman Guest

    Re: Tutorial how to use Irfanview 4.25 to rotate, shrink, & renamebatch photos

    me wrote:
    > On Tue, 06 Apr 2010 08:35:37 -0700, Paul Furman <>
    > wrote:
    >
    >> Setting 72 ppi could be useful if people want to print a low res web
    >> image; that'll cause it to print by default at a size similar to what
    >> you see on screen, where a 300 ppi setting would come out of the printer
    >> at postage stamp size, but it has no effect on file size on disk.

    >
    > That implies a fair amount of assumption about the
    > application/feature/driver set up used to print he photo, doesn't it?
    >
    > html browser vs image viewer vs image editor vs image printing app.


    Html would change things but any program that prints jpegs should use
    dpi by default for sizing. That's what it's there for. Same if you drag
    into a Word document. Granted, I often have my printer default set to
    'best fit' to fill the page.

    --
    Paul Furman
    www.edgehill.net
    www.baynatives.com

    all google groups messages filtered due to spam
    Paul Furman, Apr 7, 2010
    #6
  7. Tim

    Paul Furman Guest

    Re: Tutorial how to use Irfanview 4.25 to rotate, shrink, & renamebatch photos

    Elmo wrote:
    > On Tue, 06 Apr 2010 08:35:37 -0700, Paul Furman wrote:
    >
    >> Setting 72 ppi ... [will] cause it to print by default at a size similar to what
    >> you see on screen, where a 300 ppi setting would come out of the printer
    >> at postage stamp size, but it has no effect on file size on disk.

    >
    > Interesting.
    >
    > Ummm... so what PPI/DPI settings SHOULD we recommend for batch shrinking
    > and renaming suitable for emailing family photos to others?


    Something like 300 if it's high res pics but for grandma to print 100k
    email snaps, more like 75 dpi as she'd expect them to print the same
    size as on screen.

    > 300?
    > 600?
    > 1200?
    > ?



    --
    Paul Furman
    www.edgehill.net
    www.baynatives.com

    all google groups messages filtered due to spam
    Paul Furman, Apr 7, 2010
    #7
  8. Re: Tutorial how to use Irfanview 4.25 to rotate, shrink, & renamebatch photos

    Elmo wrote:
    > On Tue, 06 Apr 2010 08:35:37 -0700, Paul Furman wrote:
    >
    >> Setting 72 ppi ... [will] cause it to print by default at a size similar to what
    >> you see on screen, where a 300 ppi setting would come out of the printer
    >> at postage stamp size, but it has no effect on file size on disk.

    >
    > Interesting.
    >
    > Ummm... so what PPI/DPI settings SHOULD we recommend for batch shrinking
    > and renaming suitable for emailing family photos to others?
    >
    > 300?
    > 600?
    > 1200?
    > ?


    It's PPI, and definitely not DPI for what you're talking about. If
    they're just for viewing on screen, 800 x 600 is a reasonable size. If
    for printing, I'd resize to the lesser of 1000 x 1500 or whatever is the
    native number of pixels of the image.

    --
    John McWilliams
    John McWilliams, Apr 7, 2010
    #8
  9. Tim

    Tim Guest

    Paul Furman wrote:
    > Tim wrote:
    >> Elmo wrote:
    >>> Tim wrote:
    >>>
    >>>> Why are you setting the resolution to 72 pixels per inch? If they
    >>>> are to be emailed and viewed on screen the resolution doesn't
    >>>> matter at all
    >>>
    >>> What is the right answer to recommend to batch shrink common photos
    >>> to be emailed?

    >>
    >> Resolution is only applicable to printed images, or applications
    >> that show your image on a virtual piece of paper. Something like a
    >> word processor, a desktop publishing application or something with
    >> "print preview".

    >
    > Setting 72 ppi could be useful if people want to print a low res web
    > image; that'll cause it to print by default at a size similar to what
    > you see on screen, where a 300 ppi setting would come out of the
    > printer at postage stamp size, but it has no effect on file size on
    > disk.


    Maybe if you have a very old Mac, but otherwise not particularly close. That
    old line about 72 pixels per inch being the screen's resolution is much
    repeated, but quite wrong and is exactly the theme of the Scantips "Say No
    to 72dpi" site (http://www.scantips.com/no72dpi.html).
    The nominal screen resolution in Windows is 96 dpi, but that is the same for
    a 14 inch laptop or a 27 inch desktop monitor.
    On my laptop the 15 inch screen is 1400 x 1050 pixels. The screen is 12
    inches wide. So the real resolution is 1400/12 = 116.7 pixels per inch. Low
    res web images that have their resolution changed to 72 ppi would print 62%
    larger than they appear on screen.
    My 22 inch desktop screen is 1680 x 1050 pixels. The screen is 18.7 inches
    wide. The real resolution in this case is 1680/18.7 = 89.8 pixels per inch.
    Low res web images that have their resolution changed to 72 ppi would print
    25% larger than they appear on screen.


    --
    Tim
    Tim, Apr 8, 2010
    #9
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