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Thread: Reprographics - pixel resolution

  1. #1
    Join Date
    Mar 2013
    Wales - UK

    Question Reprographics - pixel resolution

    Hi there, Just wondered if someone could help. I have been very pleased with some paintings I have done recently, and was so fed up to find some of my own family derided my efforts, saying that digital art is not 'proper' art! Not like real painting! Grrr. So I decided to put some onto a data stick and get them printed off onto a canvas, way too expensive. But the techie guy who was very helpful tried to explain to me that a ptg is not good enough quality as it would pixelate. And I am still confused. I have converted them into a jpeg as he advised and the resolution seems to be 1366 x 728. Is this correct - or good enough, and could someone please advise me regarding this. Thanks.

  2. #2
    Join Date
    May 2009
    3438 ft above sea level
    Hi Gepocock

    Here's a couple of video's from photoshop artist Mark Kohr that might interest you:-

    Image Resolution

    An argument for working digitally

    Your issue lies in the mismatch between how many pixels a screen needs to display an inch of image (72dpi) and how many dots a printer needs to display that same inch of image (this number varies depending on the type of paper and the type of printer used but on average most printers like 300dpi).

    If we take a screen image at 72dpi and print it at 300dpi the pixels will have to stretch to accommodate the same width and height resulting in a pixelated image (loss of image clarity, more blurry).

    Tell your printer your target image size for print (eg. 8"x12", A4 landscape etc) and what sort of output (paper, canvas) etc and ask him for his recommendation for what size/resolution you need to make/create your image at. He will know his printers and papers/canvas best and can give you the best advise here. You can then resize your image in Artrage using the setup your printer recommended and use the advise in Marks video to repaint over your image at the new size. (pay extra attention to hard edges as these will be where the image will be most affected).

    ps/ apologies for this post appearing in spurts .... i've been having wireless router issues today
    Last edited by Juz; 04-05-2013 at 09:40 AM.
    "I paint because I love to cut mats" (Arthur Alexander)

  3. #3
    Join Date
    Feb 2011
    Berwick, Melbourne, Australia
    Hi Gepocock,
    Quote Originally Posted by gepocock View Post
    ~ But the techie guy who was very helpful tried to explain to me that a ptg is not good enough quality as it would pixelate. ~
    Just so you know, that PTG file is a format that's specific to ArtRage.
    Unless your "techie guy" has ArtRage installed on his computer, there's no way he'd be able to open the PTG file.

    As Juz already suggested, get your techie guy to tell you what format best suits his needs for printing.

    HTH, Colin

  4. #4
    *pre-press specialist here*

    Resolution for conventional offset printing is generally considered to be two times the line screen of your print:

    2*lpi (lines per inch) = ppi (pixels per inch)

    People often say things for print need to be 300 ppi and that number results from a conventional offset lithography screen of 150lpi, somewhat coarse for modern day print, but common enough. If terms like "lines per inch" mean nothing to you, don't be concerned. All that's important to understand is that for print you need a much higher resolution than you get by default in AR.

    That said however, Artrage may bog down if you move to print resolution at large image sizes. It's been my experience with earlier versions of the program that even tabloid (11x17) at 300ppi with a few layers is enough to cripple interactivity in Artrage. AR4 may have improved this, but assuming not there are compromises to be made. What I would suggest is a more moderate value of 150ppi for painting, which can then be res'd up in Photoshop by your vendor if required.

    Your tech guy probably thought you meant PNG instead of PTG. PNG is Portable Network Graphic, a format for web graphics that generally is defaulted to 72ppi, with relatively small file sizes for use in web pages. As the previous poster stated, PTG is AR's proprietary format. You would want to save out to PSD, photoshop file format, which is pretty much industry standard for passing files about with good loss-less compression.

    Assuming also that your monitor is not calibrated and that you don't use any color calibration software, you're going to want to communicate with your vendor that your images need to have sRGB profiling applied to them. A discussion of profiling is beyond the scope of this advice; it's sufficient to say that this will put the color of your image in context of most common monitors. Should you have access to Photoshop, do NOT convert your painting to CMYK. That is something your vendor should do for you, using color managed workflows. They will know best how to maintain the color fidelity of your image in the separation process. Your image may be output on printing devices that use multi-color ink systems that can produce a much wider gamut of colors than standard offset printing CMYK color spaces. By converting to CMYK yourself, you drastically limit the color of your image. Let your vendor handle such conversions.

    Finally, before getting a big painting imaged, get a reduced sized contract proof done. This will let you verify that your vendor's color conversions and setup meet with your approval before the expense of a large print. It is always worth the additional sum of money to ensure that a project will meet your expectations in its finished form.

  5. #5
    Join Date
    Mar 2013
    Wales - UK


    Thank you all for your help, I will get somethings printed soon, and try to show that this is 'proper' art LOL

  6. #6
    Join Date
    Apr 2012

    Just had a thought which might help you.

    Once you decide on a final PPI or DPI and size of canvas to print to, use math to determine your ideal pixel size at the original aspect ratio, and create a new painting at that size with your preferred canvas etc.

    Use your old low res painting as a tracing image. Apply the old image to your new painting. Manually go in with the appropriate brush and repaint areas which are aliased... (blocky) using the tracing image as the color for the paint.

    The end result should be a non-aliased close version to your original at the higher resolution for printing.


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