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Thread: image size

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    Junior Member elmut is on a distinguished road
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    image size

    hello everybody i would like to ask some question on what would be the best image resolution for printing a poster that is 140x200 centimeters. I have already a picture that has 5000x6675 pixel and 600 DPI do you think its already enough or do i have to resize the picture?

  2. #2
    Member okra is on a distinguished road
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    I would think that 600dpi is more than adequate. You would /could get away with 300 but it depends on what the poster is going to be used for?... personal, public display, at what distance will it be hung from the viewer?... etc etc.
    When viewing large format printing, 99% of the time 300dpi output is more than enough. From 6 feet away, it is impossible to see any difference between images printed at 300dpi or 600dpi.

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    PRC Member spider is a name known to all spider is a name known to all spider is a name known to all spider is a name known to all spider is a name known to all spider is a name known to all
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    Quote Originally Posted by elmut View Post
    hello everybody i would like to ask some question on what would be the best image resolution for printing a poster that is 140x200 centimeters. I have already a picture that has 5000x6675 pixel and 600 DPI do you think its already enough or do i have to resize the picture?
    you have to take in account the method of printing: offset printing with 175lpi?
    or digital printing with e.g. 1440 dpi printing resolution?

    using some math from elementary school you will find out that your image only gives an output resolution of 85 dpi! (6675 pixels / 200 cm * 2.54 = 85 dpi)

    imho this is not enough, even for digital printing. you should double the resolution with photoshop to get 170 dpi. this might be sufficient for digital printing but depends of course on the details in the image and the distance for viewing the print result.

    if you are going to offset printing with 175 lpi you have to scale the image in photoshop by factor 4 giving you 340 dpi for output. this will result in a very big file size of course.

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    Member okra is on a distinguished road
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    Damn!... that was a fgood explanation.... I knew I should have g to school more often. hahahaha... Its surprising how much we rely on maths to formulate everyday things. Have you got any more info on this calculation...? I would like to learn a bit about that side of it. Thanks. :)

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    PRC Member spider is a name known to all spider is a name known to all spider is a name known to all spider is a name known to all spider is a name known to all spider is a name known to all
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    Quote Originally Posted by okra View Post
    Damn!... that was a fgood explanation.... I knew I should have g to school more often. hahahaha... Its surprising how much we rely on maths to formulate everyday things. Have you got any more info on this calculation...? I would like to learn a bit about that side of it. Thanks. :)
    what dou you not understand in this calculation?

    the number of pixels in the image is given and is determined by the camera settings and max. resolution of the ccd chip.

    dividing the number of pixels by the length (in cm) of the output size gives you the number of pixels per centimeter for the output image.

    since 1 inch has 2.54 centimeters you will get the dpi by multiplying the dots per cm by 2.54.

    output resolutions for some printing methods are also fix values which have to be considered to get a good quality.

    btw.: please dont lead newbie members in the wrong direction by replying without the necesarry technical background.

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  8. #6
    Member okra is on a distinguished road
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    I had no intention of that what-so-ever mate... I was just commenting on how maths plays a large role in our everday lives including work. I have never bothered with that sort of calculation and that is why I said thanks for the info... I wasnt trying to or will I ever make myself out to be a pro... Im still learning.

  9. #7
    PRC Member spider is a name known to all spider is a name known to all spider is a name known to all spider is a name known to all spider is a name known to all spider is a name known to all
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    Quote Originally Posted by okra View Post
    I had no intention of that what-so-ever mate... I was just commenting on how maths plays a large role in our everday lives including work. I have never bothered with that sort of calculation and that is why I said thanks for the info... I wasnt trying to or will I ever make myself out to be a pro... Im still learning.
    i was talking about post #2:

    I would think that 600dpi is more than adequate. You would /could get away with 300 but it depends on what the poster is going to be used for?... personal, public display, at what distance will it be hung from the viewer?... etc etc.
    When viewing large format printing, 99% of the time 300dpi output is more than enough. From 6 feet away, it is impossible to see any difference between images printed at 300dpi or 600dpi.
    the 600 dpi are not the effective output resolution for the poster.
    so your comment is totally wrong as answer to the question and didnt help at all.

  10. #8
    Member okra is on a distinguished road
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    Ok, I stand corrected. That much of a mature person I am. Looks like I will ahve a lot of reading up on the matter to do to come anywhere near your levelof expertise.
    BTW, I did say thanks for the info didnt I?

  11. #9
    Junior Member zomod is on a distinguished road zomod's Avatar
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    It all depends on the print, the use of the printed image.
    If it is a digital inkjet usually 150 dpi is more than enough for this size of the image, there are exceptions such as when you print the map or in the image is too small text, but these images are the best type of vector files.

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    Junior Member typesetter is on a distinguished road
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    In fact, required resolution is determined by the image itself.
    If the image has much high-contrast detail - then it does need a higher resolution. If the image is blurry, does not contain fine details - then resolution can be significantly smaller.

    As for this particular case - depending on printing technology (i.e. offset or inkjet) your printer will inform you about optimal incoming image resolution. And if your image doesn't meet the requirement - you can "blow up" its resolution with specific plugins (Fractals Print Pro, AlienSkin Blow up, Pxl SmartScale etc). I do not recommend to use Photoshop for upscaling because of nasty artefacts bicubic interpolation does.

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    Junior Member zomod is on a distinguished road zomod's Avatar
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    >typesetter

    If the resolution of image is not less than 100 dpi, and if you choose the right format for saving from Photoshop, than no artifacts you will see. Choose these formats to save the image as a Tiff and you can put lzw compression, but do not put jpeg compression.
    Last edited by zomod; 04-07-2013 at 01:50 AM.

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  17. #12
    PRC Member spider is a name known to all spider is a name known to all spider is a name known to all spider is a name known to all spider is a name known to all spider is a name known to all
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    Quote Originally Posted by zomod View Post
    >typesetter

    If the resolution of image is not less than 100 dpi, and if you choose the right format for saving from Photoshop, than no artifacts you will see. Choose these formats to save the image as a Tiff and you can put lzw compression, but do not put jpeg compression.
    absolutely nonsense!

    as said before the required resolution depends on the image details, viewing distance and printing method.

    saving the file in photoshop as .tif doesnt help anyway if the file has been an .jpeg before (like most images from consumer digital cameras!).
    the jpeg artefacts are already in the image data even before saving the new file from photoshop.
    so you cant reduce them by changing the file type.

  18. #13
    Junior Member zomod is on a distinguished road zomod's Avatar
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    Quote Originally Posted by spider View Post
    absolutely nonsense!

    as said before the required resolution depends on the image details, viewing distance and printing method.

    saving the file in photoshop as .tif doesnt help anyway if the file has been an .jpeg before (like most images from consumer digital cameras!).
    the jpeg artefacts are already in the image data even before saving the new file from photoshop.
    so you cant reduce them by changing the file type.
    Before you write that I am talking nonsense, read what I wrote above. Naturally, I'm talking about saving from Photoshop images of normal quality, not on already damaged image Jpeg compression. And of course that photoshop is not related to these artifacts, so that nonsense - this is linked attitude Photoshop and these artifacts. Prevent artifacts apply blur filters.

    If the image was fine details or text and they were corrupted compression. Not specific filter is not able to recover to its original state, only the work by hand.
    Last edited by zomod; 04-07-2013 at 03:50 AM.

  19. #14
    PRC Member spider is a name known to all spider is a name known to all spider is a name known to all spider is a name known to all spider is a name known to all spider is a name known to all
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    Quote Originally Posted by zomod View Post
    Before you write that I am talking nonsense, read what I wrote above. Naturally, I'm talking about saving from Photoshop images of normal quality, not on already damaged image Jpeg compression. And of course that photoshop is not related to these artifacts, so that nonsense - this is linked attitude Photoshop and these artifacts. Prevent artifacts apply blur filters.

    If the image was fine details or text and they were corrupted compression. Not specific filter is not able to recover to its original state, only the work by hand.
    this topic is about image resolution for printing output!

    why are you talking about image compression, jpeg artefacts and saving files from photoshop?

    did you get the point of @elmuts question???

  20. #15
    Junior Member zomod is on a distinguished road zomod's Avatar
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    Quote Originally Posted by spider View Post
    this topic is about image resolution for printing output!

    why are you talking about image compression, jpeg artefacts and saving files from photoshop?

    did you get the point of @elmuts question???

    Did you see typesetter message, to which I replied ?
    " I do not recommend to use Photoshop for upscaling because of nasty artefacts bicubic interpolation does."


    And yes, I see what the issue elmut, I should not just in any case when the source image to the size elmut receives the output to 40 dpi, and increase the number of points he can only through interpolation in the graphics program, in any case, such a procedure he no need more than 100 dpi (because it will likely be used inkjet printing), and yes he will have to apply some filters to hide the artifacts if he does not like.
    Last edited by zomod; 04-07-2013 at 05:50 AM.

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