Newbie question - photo size by pixel

Discussion in 'Digital Photography' started by Nocturne_CVS@yahoo.com, May 7, 2006.

  1. Guest

    Hi, all

    I'm going to be submitting some photographs to a web page that has the
    following size requirement:

    "Photos must be at least 2.5MP (2.5 Million Pixels). To determine the
    amount of pixels in a photo, multiply the width by the length. For
    example: a photo which is 1700x1500 adds up to a total of 2.55 million
    pixels -"

    And I don't understand what this means. Why don't they just say, photo
    must be 4 inches by 6 inches, or whatever?

    I use a Kodak EasyShare DX7590, set at 4.4 resolution. The photos are
    huge so I resize them in PhotoImpression to 400 X 600, whatever that
    means...it works out to a 4 X 6 print.

    Anyway, sorry to sound dumb, but if someone can explain this to me.
    When I look at the site itself the photos all look like they're 3 X 5,
    but I don't know if they've been shrunk down from the size they were
    submitted at...
    , May 7, 2006
    #1
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  2. Pat Guest

    Oh, where to start.

    To start with, your screen is about 72 pixels per inch but for good
    quality printing, you need a LOT more than that. But in general, 300
    dpi (dots per inch) is about where you want to be. Some printers will
    go higher than that, but it is arguable if most people can tell the
    difference.

    If the site wants 1700x1500, that's about 5.5 inches by 5 inches, at
    300 dpi. Argueably, you can print down into the 180 dpi range, but it
    starts to show. So, they might go bigger, but figure they are looking
    for a good quality print of that size. But the same token, the same
    picture will look fine on a website at 400 x 600 at about 5 inches by
    about 8 inches -- with with a the top of the browser, the stuff at the
    bottom of the page, a little border around it, it will reasonable fill
    a screen and look good.

    Most photo sites have you post big files and the "resample" them down
    to a smaller size or a thumbnail as convenience and to get more
    pictures per page.

    So as you work on photos, work on as full size files. For many things,
    the order you do them in doesn't matter, but the second to the last
    step ever do is use "sharpen". The last step is to reduce (or
    downsample) the image for your screen. Also, when you reduce the size,
    make absolutely sure you keep a full size version because if you email
    a picture to your Aunt Minnie and she wants you to print it, you'll
    need the full size image.

    Good luck and have fun taking pictures. I hope this helps.
    Pat, May 7, 2006
    #2
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  3. Bill Guest

    wrote:

    >I'm going to be submitting some photographs to a web page that has the
    >following size requirement:
    >
    >"Photos must be at least 2.5MP (2.5 Million Pixels). To determine the
    >amount of pixels in a photo, multiply the width by the length. For
    >example: a photo which is 1700x1500 adds up to a total of 2.55 million
    >pixels -"
    >
    >And I don't understand what this means. Why don't they just say, photo
    >must be 4 inches by 6 inches, or whatever?


    Because inches and pixels are not the same value or scale.

    Google the word "pixel" for digital images.
    Then google "DPI" for printed photos.

    A digital image can be almost any size, say 40x60 pixels or 4000x6000
    pixels. Yet a 4x6 photo can have various levels of pixel density called
    dots per inch (DPI).

    It sounds like your camera is capable of taking 4.4mp images at maximum
    resolution. Submit them "as is" and you're fine.
    Bill, May 7, 2006
    #3
  4. Guest

    Thanks to both of you for your responses.

    Very helpful!


    Barbara
    , May 7, 2006
    #4
  5. wrote:
    > Hi, all
    >
    > I'm going to be submitting some photographs to a web page that has the
    > following size requirement:
    >
    > "Photos must be at least 2.5MP (2.5 Million Pixels). To determine the
    > amount of pixels in a photo, multiply the width by the length. For
    > example: a photo which is 1700x1500 adds up to a total of 2.55 million
    > pixels -"


    The reason they don't say "4x6" or "5x7" is that it gives no guidance
    for the number of pixels that make up the image; you could have a 4 x6
    picture that has but a few thousand pixels, and would look horrible even
    at screen resolutions of ca. 100 ppi (it used to be 72; old monitors
    still are), or it could be a huge file of several thousands of pixels
    per edge (giving several dozens of megabytes to store).

    So, rather than have you calculate out that a 8 x 10" image at 300 ppi
    would give them more than they want, they just tell you the number of
    pixels; the ppi doesn't matter until they size it up to their specs.

    --
    John McWilliams
    John McWilliams, May 7, 2006
    #5
  6. Shawn Hirn Guest

    In article <>,
    wrote:

    > Hi, all
    >
    > I'm going to be submitting some photographs to a web page that has the
    > following size requirement:
    >
    > "Photos must be at least 2.5MP (2.5 Million Pixels). To determine the
    > amount of pixels in a photo, multiply the width by the length. For
    > example: a photo which is 1700x1500 adds up to a total of 2.55 million
    > pixels -"
    >
    > And I don't understand what this means. Why don't they just say, photo
    > must be 4 inches by 6 inches, or whatever?


    Doesn't the company that operates that web site have an email address of
    phone number to use for asking tech support questions? If so, I suggest
    you contact the company to see what they say.
    Shawn Hirn, May 7, 2006
    #6
  7. On 6 May 2006 17:00:37 -0700, <> wrote:
    > Hi, all
    >
    > I'm going to be submitting some photographs to a web page that has the
    > following size requirement:
    >
    > "Photos must be at least 2.5MP (2.5 Million Pixels). To determine the
    > amount of pixels in a photo, multiply the width by the length. For
    > example: a photo which is 1700x1500 adds up to a total of 2.55 million
    > pixels -"
    >
    > And I don't understand what this means. Why don't they just say, photo
    > must be 4 inches by 6 inches, or whatever?
    >
    > I use a Kodak EasyShare DX7590, set at 4.4 resolution. The photos are
    > huge so I resize them in PhotoImpression to 400 X 600, whatever that
    > means...it works out to a 4 X 6 print.


    Short answer: Don't resize the photos that come out of the camera, and
    you'll be fine.

    Other people have already posted the longer explanation.

    -dms
    Daniel Silevitch, May 7, 2006
    #7
  8. Shawn Hirn wrote:
    > In article <>,
    > wrote:
    >
    >> Hi, all
    >>
    >> I'm going to be submitting some photographs to a web page that has the
    >> following size requirement:
    >>
    >> "Photos must be at least 2.5MP (2.5 Million Pixels). To determine the
    >> amount of pixels in a photo, multiply the width by the length. For
    >> example: a photo which is 1700x1500 adds up to a total of 2.55 million
    >> pixels -"
    >>
    >> And I don't understand what this means. Why don't they just say, photo
    >> must be 4 inches by 6 inches, or whatever?

    >
    > Doesn't the company that operates that web site have an email address of
    > phone number to use for asking tech support questions? If so, I suggest
    > you contact the company to see what they say.


    This is not really a technical support question in many ways, and I
    believe the OP got plenty of correct info.

    --
    john mcwilliams
    John McWilliams, May 7, 2006
    #8
  9. ASAAR Guest

    On 6 May 2006 17:00:37 -0700, wrote:

    > I use a Kodak EasyShare DX7590, set at 4.4 resolution. The photos are
    > huge so I resize them in PhotoImpression to 400 X 600, whatever that
    > means...it works out to a 4 X 6 print.


    The photos may appear huge on your computer's monitor, but even
    without resizing them, they'll fit on a 4 x 6 print, minus a small
    amount lost due to the DX7690's 4.4 mp images not having exactly the
    same aspect ratio as the 4 x 6 print paper.

    If you mean that the resized images have a 400 pixel by 600 pixel
    dimension, then your 4 x 6 prints are probably much less sharp than
    they could be. By reducing the original 4.4 megapixel images to
    only 1/4 megapixels (400 x 600 == 240,000), you've thrown away 94%
    of what the DX7590's sensor captured. You may have selected 400 x
    600 because it matches the 4:6 aspect ratio of the 4" x 6" print
    size. You could also resize your images to 800 x 1200, 1200 x 1800
    or 1600 x 2400 pixels, and they'd all have the same 4:6 aspect ratio
    but they'd save as larger files, containing more image data. Try
    reprinting one of your previous shots, this time after resizing the
    image to 1200 x 1800. It should be quite a bit sharper, but if the
    difference doesn't seem that great (and it may not, since the 4 x 6
    print is fairly small), compare the two prints with a small
    magnifier. If you do, you'll probably be amazed at how poor the
    print made from the 400 x 600 pixel images appears. I hope that you
    saved the original images, and didn't replace them with the smaller
    resized versions. If you ever make larger prints such as 5" x 7"
    or 8" x 10", you'll easily see the drastically lower quality that
    you'll get from 400 x 600 pixel images.
    ASAAR, May 7, 2006
    #9
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