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Thread: Rescaling painting - increasing DPI question & related printing output questions

  1. #1
    Join Date
    Feb 2009
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    Rescaling painting - increasing DPI question & related printing output questions

    When rescaling a painting and increasing the DPI, say from 150dpi to 300dpi, is the pixel data really converted into finer detail? Same question if you increase the dpi, and give instructions to keep the same painting dimensions? Reason for question - creating paintings for printing on canvas - dpi conversion realities will affect output.

    A related question: Any recommended dpi settings in ArtRage for paintings destined for printing on canvas with commercial ink-jet processes?

    Finally, I note that ArtRage doesn't seem to allow for paintings much larger than, say, 24X36 inches at 150dpi with 2 ghz of RAM. Any work-around feedback on the limitation with attempts to create large files for large paintings is welcomed.

    Thanks, Byron
    (ArtRage 2.5, Full Version, Windows Vista, Mouse)


  2. #2
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    Any time you scale a painting up, you will lose detail. ArtRage will interpolate as best it can, but we can't add detail where there wasn't any so you definitely will not end up with as much there when you do this.

    Increasing the DPI value while keeping the same physical dimensions ( inches, cm etc ) will have the same effect because you're adding pixels so Artrage is scaling the image up.

    I'm not sure on the recommended dpi settings for commercial printers. One of our other forums users might have experience with this though.

    Size of images is dependant on RAM. If you find that you are hitting the limit, working with less layers may help to keep the overhead down somewhat.
    Dave
    Resident Bug-Hunter
    Ambient Design

  3. #3
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    For Dave: Clarifcation question from your response:

    Dave, thanks much. I think I followed you but I'm not sure I'm clear on your response to the second question. Following is how I interpret your feedback, but I'm not sure my interpretation is correct. Can you confirm and clarify?

    My interpretation: If I scale a painting up in ArtRAge, say from 72 dpi to 300 dpi, AND RETAIN THE EXACT DEMINSIONS OF THE ORIGINAL, the new scaled-up painting will be a "true" 300 dpi file. In other words, the DPI is truly "scale up". There will be more pixels in the same physical space. Is this a correct understanding?

    Meanwhile, as you answer in the first question, if I increase the dimensions proportionally with the DPI increase, there will be no dpi improvement, indeed it may be worse, since there will be the same or fewer pixels in a given area of space. Is this a correct understanding of the first question?

    Is this all about right, or am I somewhere in left field?

    Thanks again Dave,
    Byron

  4. #4
    Join Date
    Feb 2009
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    Byron - you're correct. All you're doing when changing the dpi is adjusting pixel density. The 'image size' - 8x10, or 4x6, etc. really means little. It's just a tag, really. Most printers will recommend you send them a file with at LEAST 150 dpi for the print size you are getting.

    It can all get really confusing, because there are really 2 things at work here - ppi and dpi. ppi is pixels per inch. A typical computer monitor uses 72 pixels in each inch of screen space. Therefore my 1600x1050 monitor should be 22 inches wide by 14 tall. Which it is. Roughly. Pixel sizes differ on every monitor. Therefore, when you open an image in AR, at say 8x10 inches at 72 dpi, it should come close to measuring an actual 8x10 on your screen at 100%. In this case, ppi and dpi are equal. If you open that same 8x10 at 300dpi, since your monitor can only display 72 pixels per inch, you have to 'zoom out' by well more than 50% to display the image at 8x10 inches on your screen. This means you can squeeze a lot more detail on that canvas, because of the greater pixel density. You could also open an image at 16x20 at 150dpi and have the EXACT same number of pixels to work with. The print size (or 'pixel dimension') doesn't really matter. If you're looking to print your work, determine the size you'd like to print first. If it is an 10x8 inches, for instance, and your printer wants 180dpi for the best quality, multiply 10x180= 1800 and 8x180=1440. Create the image as 1800x1440 and there will be enough detail to print it at 10x8. You can see how this works in AR by creating a new image and choosing a pixel size (use the default - mine is 1680x1016). Change the dpi to 10. Then change from pixels to inches. 168 inches x 102! -

    Ok, that was really long-winded. I hope this makes sense. If you already knew this, I apologize.

  5. #5
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    Thanks Damian

    Thanks Damian,
    No, it's not long-winded, it's very helpful.Thanks for the benefit of your experience and for being thorough. I think I'm beginning to understand this better and very much appreciate your help.
    Be well,
    Byron

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