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Thread: dpi question

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    dpi question

    My wife has to submit some photos for a jewelry contest. They want the pictures to be 300 dpi. and

    I set my camera on the highest settings and took some pics.
    When I view them in Irfanview and click on Resize it says the pic is 180 dpi. I change it to 300 dpi and save it.

    Will this meet the requirments for 300 dpi???

    How does it get 300 dpi out of a 180 dpi picture???

    Next they want the size to be at least 1920 pixels on one side.
    At my highest setting it makes pictures 2048x 1536.
    I crop one side to a little over 1920 on one side, so I think I am ok on the size requiment.

    Thanks for the help
    Michael

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    Re: dpi question

    See if this helps.
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    Re: dpi question

    Thanks Doc
    I see the the DPi is really a printer setting, so it is just tell the printer to put 300 dpi instead of the othe 180.

    Thanks again
    Michael

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    Re: dpi question

    From here.....

    "An 8-megapixel camera captures up to 8 million pixels per photo. To ensure good print quality, you will want to print at about 300 dots per inch (dpi) or higher, which we'll consider to be roughly the same thing as pixels per inch. Suppose your 8-megapixel camera takes a picture at 3200x2400. To calculate the photo size that will print at acceptable quality at this resolution, divide each side by 300 dpi. So, 3200 divided by 300 is 10.67, and 2400 divided by 300 is 8. Therefore, you will be able to print an 8"x10" picture with good quality. Similarly, you could use the 1600x1200 resolution setting to print a 4"x6" photo.

    If you’re planning to use an image editing program to increase the pixels per inch of your photos onscreen before printing them, keep in mind that the program will decrease the dimensions of your photo to compensate. The program will essentially scrunch the pixels together to eliminate tiny white spaces and the "washed-out" look they cause. That will cause the total image size to shrink as the quality increases. So, if you want to produce high-quality prints of large photos, you'll need to use a powerful camera that’s set on the highest possible setting.
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    Re: dpi question

    That looks like a worthwhile site. Thanks, Doc.

    Ian

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    Re: dpi question

    The information is good. The page is on the Best Buy site. Not necessarily someplace I would go looking for technical information or answers. <img src=/S/laugh.gif border=0 alt=laugh width=15 height=15>
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    [quote name='DocWatson' post='760231' date='21-Feb-09 15:17']From here.....

    "The program will essentially scrunch the pixels together to eliminate tiny white spaces and the "washed-out" look they cause."[/quote]What a load of codswallop! There is no 'white space' between the pixels in an image.
    Cheers,

    Paul Edstein
    [MS MVP - Word]

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    [quote name='macropod' post='761702' date='25-Feb-09 22:55']What a load of codswallop! There is no 'white space' between the pixels in an image.[/quote]

    Really ??? What color is it then ???
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    [quote name='DocWatson' post='761709' date='26-Feb-09 13:45']Really ??? What color is it then ???[/quote]Let's put it another way - there is no space between the pixels in an image.
    Cheers,

    Paul Edstein
    [MS MVP - Word]

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    [quote name='macropod' post='761713' date='25-Feb-09 23:55']Let's put it another way - there is no space between the pixels in an image.[/quote]

    I always thought pixels were round. If that is true (and I've been wrong before) then there has to be a space between them unless they overlap. Why else would an image pixelate when you enlarge it too much ??
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    [quote name='DocWatson' post='761903' date='26-Feb-09 10:14']I always thought pixels were round. If that is true (and I've been wrong before) then there has to be a space between them unless they overlap. Why else would an image pixelate when you enlarge it too much ??[/quote]
    In a data file, pixels are a grid of data with no gaps. On an output device, there may be thin unlit areas (e.g., on an LCD monitor) or extremely tiny unprinted areas (e.g., on a printout).

    I think the criticism of the description is that regardless of the resolution of the image, the output device tries to fill the space completely. You would never see the pixels spaced apart; rather, they would be enlarged. So changing the resolution does not affect white space in your printouts, but it could affect the quality of the image (e.g., smoothness of edges, level of fine detail).

    Of course, if someone can prove this supposition wrong with their print device, have at it.

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    [quote name='DocWatson' post='761903' date='27-Feb-09 05:14']I always thought pixels were round. If that is true (and I've been wrong before) then there has to be a space between them unless they overlap. Why else would an image pixelate when you enlarge it too much ??[/quote]Hi Doc,

    Pixels don't have a physical shape. In an image capture device, the CMOS/CCD elements that detect the light may be square, round, hexagonal, etc, with gaps of various sizes between them but, due to the way the technology works, no account is taken of these gaps. Most digital cameras, for example, use a Bayer sensor in which two green, one blue and one red sensel combine to form a single pixel. Each sensel actually captures a slightly different portion of the image, but the offsets and gaps between them are so small their amalgamation as a single pixel is inconsequantial.

    Whatever graphics app you use to process the image treats the pixels as being a tightly-packed array (ie no physical gaps) - I've never seen a graphics apps that tried to insert a gap between the pixels. In any event, how would one know what gap to use? Every capture device is different.

    As Jefferson says:
    On an output device, there may be thin unlit areas (e.g., on an LCD monitor) or extremely tiny unprinted areas (e.g., on a printout).
    If such gaps do exist, no amount of resizing the image will eliminate them. That's because the gaps are limitations of the hardware and playing with the software can't overcome that. Thus, making an image smaller won't reduce the gaps in the output and can't change the "washed-out" look referred to in the article.
    Cheers,

    Paul Edstein
    [MS MVP - Word]

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    Thanks Paul !! That's a bit over my head technically, but I think I understand the gist of what you are saying.
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    [quote name='jscher2000' post='761965' date='26-Feb-09 17:09']Of course, if someone can prove this supposition wrong with their print device, have at it. [/quote]

    I'll pass.
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