picture resolution

Discussion in 'Digital Photography' started by Bill Bowden, Aug 1, 2007.

  1. Bill Bowden

    Bill Bowden Guest

    I want to print 4X6 photos and maintain good resolution. The original
    JPG files from my 'cannon power shot 460' vary around 1.2 to 2 megs.
    When I load these photos into photoshop, the dimensions vary from
    36X27 inches to 22X16 at 72 pixels per inch.

    If I change the image size in photoshop to 4X6 inches and 72 pix per
    inch, producing a much smaller file, will I get the same resolution on
    the small print that I would get on a larger 36X27?

    Is there any advantage to adjusting the pix/inch to a higher number
    above 72, or will the printer at WalMart be able to use it?

    Thanks,

    -Bill
    Bill Bowden, Aug 1, 2007
    #1
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  2. Bill Bowden wrote:
    > I want to print 4X6 photos and maintain good resolution. The original
    > JPG files from my 'cannon power shot 460' vary around 1.2 to 2 megs.
    > When I load these photos into photoshop, the dimensions vary from
    > 36X27 inches to 22X16 at 72 pixels per inch.
    >
    > If I change the image size in photoshop to 4X6 inches and 72 pix per
    > inch, producing a much smaller file, will I get the same resolution on
    > the small print that I would get on a larger 36X27?
    >
    > Is there any advantage to adjusting the pix/inch to a higher number
    > above 72, or will the printer at WalMart be able to use it?


    You've got the wrong idea here. You don't resample your images to
    downsize them, you just change the inches dimensions, and let the
    program increase the pixel pitch accordingly. If you aren't getting more
    ppi at the smaller sizes, then you are doing something wrong or your
    photo program is shit. Recommend Photoshop Elements.

    Gary Eickmeier
    Gary Eickmeier, Aug 1, 2007
    #2
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  3. Bill Bowden

    Dave Cohen Guest

    Bill Bowden wrote:
    > I want to print 4X6 photos and maintain good resolution. The original
    > JPG files from my 'cannon power shot 460' vary around 1.2 to 2 megs.
    > When I load these photos into photoshop, the dimensions vary from
    > 36X27 inches to 22X16 at 72 pixels per inch.
    >
    > If I change the image size in photoshop to 4X6 inches and 72 pix per
    > inch, producing a much smaller file, will I get the same resolution on
    > the small print that I would get on a larger 36X27?
    >
    > Is there any advantage to adjusting the pix/inch to a higher number
    > above 72, or will the printer at WalMart be able to use it?
    >
    > Thanks,
    >
    > -Bill
    >

    The 72 number is applicable to the monitor, which will always display
    the same pixel per inch depending on the settings. Forget it.
    What you are looking for is the file data. For a 4x6 print 1600x1200 or
    higher resolution is fine. From the file size you quote sounds like you
    are shooting a little higher than that. Just crop to select the content
    you want to retain. Not familiar with PS but aim to crop to a 3:2 ratio
    and the print will be pretty much what you see on the monitor.
    Dave Cohen
    Dave Cohen, Aug 1, 2007
    #3
  4. Bill Bowden

    DaveB Guest

    On Tue, 31 Jul 2007 19:52:06 -0400, Gary Eickmeier <>
    wrote:

    >
    >
    >Bill Bowden wrote:
    >> I want to print 4X6 photos and maintain good resolution. The original
    >> JPG files from my 'cannon power shot 460' vary around 1.2 to 2 megs.
    >> When I load these photos into photoshop, the dimensions vary from
    >> 36X27 inches to 22X16 at 72 pixels per inch.
    >>
    >> If I change the image size in photoshop to 4X6 inches and 72 pix per
    >> inch, producing a much smaller file, will I get the same resolution on
    >> the small print that I would get on a larger 36X27?
    >>
    >> Is there any advantage to adjusting the pix/inch to a higher number
    >> above 72, or will the printer at WalMart be able to use it?

    >
    >You've got the wrong idea here. You don't resample your images to
    >downsize them, you just change the inches dimensions, and let the
    >program increase the pixel pitch accordingly. If you aren't getting more
    > ppi at the smaller sizes, then you are doing something wrong or your
    >photo program is shit. Recommend Photoshop Elements.
    >
    >Gary Eickmeier


    Downsizing in PhotoShop is a poor option. It only has last-century's bicubic
    resampling built-in. You will lose all manner of fine detail when using it for
    any image manipulation methods like resizing, leveling, perspective corrections,
    lens-distortion filters, etc. All your downsized images will be soft and appear
    to lose focus. Find a program that uses Lanczos routines. If you want a program
    better than and does more than PhotoShop try PhotoLine 32. It even includes the
    latest Lanczos-8 option for all image manipulation tools. You presently can't
    get better than that. Even freeware IrfanView's Lanczos algorithm beats
    PhotoShop for downsizing.

    You really don't get what you pay for these days. This is concrete proof.
    DaveB, Aug 1, 2007
    #4
  5. Bill Bowden

    ray Guest

    On Tue, 31 Jul 2007 16:23:30 -0700, Bill Bowden wrote:

    > I want to print 4X6 photos and maintain good resolution. The original
    > JPG files from my 'cannon power shot 460' vary around 1.2 to 2 megs.
    > When I load these photos into photoshop, the dimensions vary from
    > 36X27 inches to 22X16 at 72 pixels per inch.
    >
    > If I change the image size in photoshop to 4X6 inches and 72 pix per
    > inch, producing a much smaller file, will I get the same resolution on
    > the small print that I would get on a larger 36X27?
    >
    > Is there any advantage to adjusting the pix/inch to a higher number
    > above 72, or will the printer at WalMart be able to use it?


    They should print fine, as is.


    >
    > Thanks,
    >
    > -Bill
    ray, Aug 1, 2007
    #5
  6. Bill Bowden

    Victek Guest

    > Is there any advantage to adjusting the pix/inch to a higher number
    > above 72, or will the printer at WalMart be able to use it?
    >


    You don't need to mess with the ppi at all. Just crop the pictures to the 4
    x 6 aspect ratio. If you don't crop them the way you want in advance the
    machine at Wal-mart will crop them for you, and the result may not be what
    you expect.
    Victek, Aug 1, 2007
    #6
  7. Bill Bowden wrote:
    > I want to print 4X6 photos and maintain good resolution. The original
    > JPG files from my 'cannon power shot 460' vary around 1.2 to 2 megs.
    > When I load these photos into photoshop, the dimensions vary from
    > 36X27 inches to 22X16 at 72 pixels per inch.
    >
    > If I change the image size in photoshop to 4X6 inches and 72 pix per
    > inch, producing a much smaller file, will I get the same resolution on
    > the small print that I would get on a larger 36X27?


    No, and please don't do that! You'd do that only for web display or
    E-mailing a small image.

    You are best off not resizing at all unless you are over 400 or so ppi.
    >
    > Is there any advantage to adjusting the pix/inch to a higher number
    > above 72, or will the printer at WalMart be able to use it?



    PPI means little for monitor display in PS, as most default settings
    will show the whole image.

    OTOH, you might want to check "Unsampled" in Image Size in PS, and set
    it to a ppi such as 300; the size in inches will then appear as a more
    realistic number. That will also allow you to get used to pixel
    dimensions and allow you to, ah, size up a photo for its printing
    potential at high rez.

    --
    john mcwilliams
    John McWilliams, Aug 1, 2007
    #7
  8. Bill Bowden

    Jim Townsend Guest

    Bill Bowden wrote:

    > I want to print 4X6 photos and maintain good resolution. The original
    > JPG files from my 'cannon power shot 460' vary around 1.2 to 2 megs.
    > When I load these photos into photoshop, the dimensions vary from
    > 36X27 inches to 22X16 at 72 pixels per inch.


    Pixles per inch is derived by dividing the pixels in an image by
    the desired print size in inches. The formula is:

    PPI = Pixels divided by Inches

    The PPI your photoediting program is showing you is NOTHING MORE
    than the formula above (Grab a calculator next time you're editing
    some images and you'll see that's ALL it is).

    The PPI you see assigned to an image in your editing program or
    whatever image viewer you use is showing you the PROPOSED print
    size. It has nothing to do with the quality of the file as it sits
    on your memory card or disk. It has nothing to do with the file size
    or the quality of the pixels. Until an image is actually printed,
    this PPI value is completely meaningless.

    That's it. That's *everything* there is to know about PPI.

    Now for some practical examples:

    If you have an image that's 1000 pixels wide and spread those
    pixels across 10 inches of paper, then you will have a print
    resolution of 1000 pixels / 10 inches = 100 PPI

    Now take the SAME 1000 pixel image and spread those pixels
    across 2 inches and you have 1000 pixels / 2 inches = 500 PPI

    If someone says they printed an image 6 inches wide at 300 PPI,
    then the image was 300 PPI X 6 inches = 1800 pixels wide.

    Your 36 x 27 image @ 72 PPI is about 2592 X 1944 Pixels

    36 inches X 72 PPI = 2592 Pixels
    27 inches X 72 PPI = 1944 Pixels

    If you change the inches in your editor (with resample image off)
    to 8.5 X 6.48 then the PPI will change from 72 to 300. You're
    spreading your pixels across a smaller area, so you get more pixels
    in each inch.

    Just hand your images to your printer as they are. They will print
    it to the size you specify.

    > If I change the image size in photoshop to 4X6 inches and 72 pix per
    > inch, producing a much smaller file, will I get the same resolution on
    > the small print that I would get on a larger 36X27?


    A 4 X 6 image resampled to 72 PPI would be:

    4 inches X 72 PPI = 288 pixels
    6 inches X 72 PPI = 432 pixels

    You DON'T want to try print a 288 X 432 pixel image.

    Resampling is used when you want to force printing at a
    certain PPI.

    For example. You have an image that's 2000 pixels wide.
    You want to print that image across 10 inches of paper
    at 300 Pixels per inch. You can't do this.

    This is mathematically impossible.

    2000 pixels / 10 = 200 pixels per inch. There is no
    way to spread 2000 pixels across 10 inches of paper and
    have 300 pixels on every inch.

    In this case you would turn resample image on and tell
    photoshop you want the image printed 10 inches at 300 PPI.

    Now Photoshop will resample the image and add pixels increasing
    them from 2000 pixels to 3000 pixels. This resampled image can
    now print at 300 PPI.

    3000 pixels / 10 inches = 300 PPI
    Jim Townsend, Aug 1, 2007
    #8
  9. Bill Bowden

    Bill Bowden Guest

    On Jul 31, 6:22 pm, John McWilliams <> wrote:
    > Bill Bowden wrote:
    > > I want to print 4X6 photos and maintain good resolution. The original
    > > JPG files from my 'cannon power shot 460' vary around 1.2 to 2 megs.
    > > When I load these photos into photoshop, the dimensions vary from
    > > 36X27 inches to 22X16 at 72 pixels per inch.

    >
    > > If I change the image size in photoshop to 4X6 inches and 72 pix per
    > > inch, producing a much smaller file, will I get the same resolution on
    > > the small print that I would get on a larger 36X27?

    >
    > No, and please don't do that! You'd do that only for web display or
    > E-mailing a small image.
    >
    > You are best off not resizing at all unless you are over 400 or so ppi.
    >


    I need to resize because I want to copy and paste picture segments
    from different pictures into a new one. Some of the segments need to
    be larger, and others smaller.


    >
    >
    > > Is there any advantage to adjusting the pix/inch to a higher number
    > > above 72, or will the printer at WalMart be able to use it?

    >
    > PPI means little for monitor display in PS, as most default settings
    > will show the whole image.
    >
    > OTOH, you might want to check "Unsampled" in Image Size in PS, and set
    > it to a ppi such as 300; the size in inches will then appear as a more
    > realistic number. That will also allow you to get used to pixel
    > dimensions and allow you to, ah, size up a photo for its printing
    > potential at high rez.
    >


    If I set pix/inch to 400, with resample off, the size reduces to 6.5 X
    4.8 inches, but the filesize is still huge at 650K. Do I really need
    that much resolution for the printer at Wal-Mart, or will a picture at
    72 pix/inch look just as good?
    What are the limits of the "One Hour Photo" printers?

    -Bill


    > --
    > john mcwilliams
    Bill Bowden, Aug 1, 2007
    #9
  10. Bill Bowden wrote:
    > On Jul 31, 6:22 pm, John McWilliams <> wrote:
    >> Bill Bowden wrote:
    >>> I want to print 4X6 photos and maintain good resolution. The original
    >>> JPG files from my 'cannon power shot 460' vary around 1.2 to 2 megs.
    >>> When I load these photos into photoshop, the dimensions vary from
    >>> 36X27 inches to 22X16 at 72 pixels per inch.
    >>> If I change the image size in photoshop to 4X6 inches and 72 pix per
    >>> inch, producing a much smaller file, will I get the same resolution on
    >>> the small print that I would get on a larger 36X27?

    >> No, and please don't do that! You'd do that only for web display or
    >> E-mailing a small image.
    >>
    >> You are best off not resizing at all unless you are over 400 or so ppi.
    >>

    >
    > I need to resize because I want to copy and paste picture segments
    > from different pictures into a new one. Some of the segments need to
    > be larger, and others smaller.
    >
    >
    >>
    >>> Is there any advantage to adjusting the pix/inch to a higher number
    >>> above 72, or will the printer at WalMart be able to use it?

    >> PPI means little for monitor display in PS, as most default settings
    >> will show the whole image.
    >>
    >> OTOH, you might want to check "Unsampled" in Image Size in PS, and set
    >> it to a ppi such as 300; the size in inches will then appear as a more
    >> realistic number. That will also allow you to get used to pixel
    >> dimensions and allow you to, ah, size up a photo for its printing
    >> potential at high rez.
    >>

    >
    > If I set pix/inch to 400, with resample off, the size reduces to 6.5 X
    > 4.8 inches, but the filesize is still huge at 650K. Do I really need
    > that much resolution for the printer at Wal-Mart, or will a picture at
    > 72 pix/inch look just as good?
    > What are the limits of the "One Hour Photo" printers?


    No, 72 ppi will suck. One easy way is to set a crop at 4 x 6 at 300 ppi;
    then your chances for a good print increase. Also, set for sRGB if not
    already in that color space.

    BTW, fwiw, 650 K is a tiny size for many print jobs,tho not for 4 x 6's
    Good luck!

    --
    John McWilliams
    John McWilliams, Aug 1, 2007
    #10
  11. Bill Bowden

    Bob Williams Guest

    Bill Bowden wrote:
    > I want to print 4X6 photos and maintain good resolution. The original
    > JPG files from my 'cannon power shot 460' vary around 1.2 to 2 megs.
    > When I load these photos into photoshop, the dimensions vary from
    > 36X27 inches to 22X16 at 72 pixels per inch.
    >
    > If I change the image size in photoshop to 4X6 inches and 72 pix per
    > inch, producing a much smaller file, will I get the same resolution on
    > the small print that I would get on a larger 36X27?
    >
    > Is there any advantage to adjusting the pix/inch to a higher number
    > above 72, or will the printer at WalMart be able to use it?
    >
    > Thanks,
    >
    > -Bill
    >

    Choose the CROP tool.
    Set it for 6"x 4"
    Set the RESOLUTION to 300 ppi. (400 ppi is ok but is probably overkill).
    Crop the picture just the way you like it.
    Voila! Your image will print at exactly 4" X 6" and 300 ppi.
    Some commercial printers can utilize 400 ppi, and some can't.
    If it can't, it will resample your image to 300ppi or whatever is the
    maximum resolution it can handle.
    You will NOT be able to tell the difference between a 6x4 printed at
    300ppi or 400ppi.
    Bob Williams

    Bob Williams
    Bob Williams, Aug 1, 2007
    #11
  12. Bill Bowden

    Ray Paseur Guest

    Bill Bowden <> wrote in news:1185924210.534061.86490
    @k79g2000hse.googlegroups.com:

    > I want to print 4X6 photos and maintain good resolution. The original
    > JPG files from my 'cannon power shot 460' vary around 1.2 to 2 megs.
    > When I load these photos into photoshop, the dimensions vary from
    > 36X27 inches to 22X16 at 72 pixels per inch.
    >
    > If I change the image size in photoshop to 4X6 inches and 72 pix per
    > inch, producing a much smaller file, will I get the same resolution on
    > the small print that I would get on a larger 36X27?
    >
    > Is there any advantage to adjusting the pix/inch to a higher number
    > above 72, or will the printer at WalMart be able to use it?
    >
    > Thanks,
    >
    > -Bill
    >


    Bill: the rest of the advice in this thread looks pretty good and I won't
    dwell on that, but I have some experience with Costco printing (not
    Walmart) that I'd be glad to share. Go visit your retailer and talk to the
    folks who run the photo print shop. Explain what you've got and what you'd
    like to achieve. They will be glad to help you establish a workflow that
    will get you picture-perfect results every time. I have found Costco's
    machines to be perfectly profiled and they give me spot-on color. Can't
    speak for Walmart, but I would expect similar, highly professional results.
    Good luck!
    Ray Paseur, Aug 1, 2007
    #12

  13. >
    >
    > Bill Bowden wrote:


    >> Is there any advantage to adjusting the pix/inch to a higher number
    >> above 72, or will the printer at WalMart be able to use it?

    >
    >

    The printers at WalMart ignore the dpi or size figures entirely. They
    just scale the image to fit the size print you pay for, keeping
    as much resolution as they can.

    Doug McDonald
    Doug McDonald, Aug 1, 2007
    #13
  14. Bill Bowden

    Dave Cohen Guest

    John McWilliams wrote:
    > Bill Bowden wrote:
    >> On Jul 31, 6:22 pm, John McWilliams <> wrote:
    >>> Bill Bowden wrote:
    >>>> I want to print 4X6 photos and maintain good resolution. The original
    >>>> JPG files from my 'cannon power shot 460' vary around 1.2 to 2 megs.

    <snipped>
    >>
    >> I need to resize because I want to copy and paste picture segments
    >> from different pictures into a new one. Some of the segments need to
    >> be larger, and others smaller.
    >>
    >>


    Well, that's quite a switch from my understanding of your original post.
    Your initial post led me to believe you were fairly new to this stuff
    and just wanted to print a 4x6 and judging by the response so did others.

    I'm not familiar with PS. In PhotoPlus, I bring up the photo to be
    inserted in a new window, copy what I want to the clipboard, switch to
    the main window and paste as a new layer. Now this is where it gets
    editor dependent. In PhotoPlus I cannot resize a layer, so I use the
    deform tool which does quite nicely. Once resized you can position as
    needed. The editor will adjust sampling as needed.
    Dave Cohen
    Dave Cohen, Aug 1, 2007
    #14
  15. Dave Cohen wrote:
    > John McWilliams wrote:
    >> Bill Bowden wrote:
    >>> On Jul 31, 6:22 pm, John McWilliams <> wrote:
    >>>> Bill Bowden wrote:
    >>>>> I want to print 4X6 photos and maintain good resolution. The original
    >>>>> JPG files from my 'cannon power shot 460' vary around 1.2 to 2 megs.

    > <snipped>
    >>>
    >>> I need to resize because I want to copy and paste picture segments
    >>> from different pictures into a new one. Some of the segments need to
    >>> be larger, and others smaller.
    >>>
    >>>

    >
    > Well, that's quite a switch from my understanding of your original post.
    > Your initial post led me to believe you were fairly new to this stuff
    > and just wanted to print a 4x6 and judging by the response so did others.
    >
    > I'm not familiar with PS. In PhotoPlus, I bring up the photo to be
    > inserted in a new window, copy what I want to the clipboard, switch to
    > the main window and paste as a new layer. Now this is where it gets
    > editor dependent. In PhotoPlus I cannot resize a layer, so I use the
    > deform tool which does quite nicely. Once resized you can position as
    > needed. The editor will adjust sampling as needed.


    I overlooked that part.

    Bill: In PS, just drag the layer of each image into a new canvas that's
    sized the way you want with the right PPI. You'll see that PS wants all
    layers to be the same ppi, so change them all to, say, 300 ppi without
    resampling. Now you can re-size each layer with the Transform tool
    (Cmd.T on Mac), and save as .PSD. Then Save As for a jpeg you can take
    to the printer.

    --
    john mcwilliams
    John McWilliams, Aug 1, 2007
    #15
  16. DaveB wrote:
    > On Tue, 31 Jul 2007 19:52:06 -0400, Gary Eickmeier <>
    > wrote:


    >>You've got the wrong idea here. You don't resample your images to
    >>downsize them, you just change the inches dimensions, and let the
    >>program increase the pixel pitch accordingly. If you aren't getting more
    >> ppi at the smaller sizes, then you are doing something wrong or your
    >>photo program is shit. Recommend Photoshop Elements.
    >>
    >>Gary Eickmeier

    >
    >
    > Downsizing in PhotoShop is a poor option. It only has last-century's bicubic
    > resampling built-in.


    I think I made it clear that you don't want to resample when downsizing.

    Gary Eickmeier
    Gary Eickmeier, Aug 2, 2007
    #16
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