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Thread: Question about up-rezing

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    Subscriber Member TRSmith's Avatar
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    Question about up-rezing

    I have an image that's marginal in terms of resolution. This is not a photo I've taken, but one I have to use. The current dimensions are 24 inches wide by 15.4 inches high at 125 ppi. I must maintain the 125 ppi as a minimum but need the wide dimension to be 32 inches (an increase of about 134%).

    Is it even possible to do that? Is it possible to do it without additional software? If not, is there a software that might make it possible or get me close?

    Thanks in advance, I never upsize images so this is all new to me.

    Tim

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    Re: Question about up-rezing

    Tim, try this using Photoshop.
    First Step: Image Size - change resolution to 150, width to 38.4" (20% over target), use Bicubic Smoother, click ok
    Second Step: Image Size - change resolution back to 125, width to 32, use Bicubic Sharper, ok
    Also - as an intermediate step between the first and second step above you can add some sharpening targeted at edges (USM 1 or 2 pixels wide).

    If this is not satisfactory use the stair-step method by increasing in 10% increments in Photoshop using bicubic smoother until you are about 20% over target then downsize in one step using bicubic sharper.

    Credit goes to GetDPI Workshops for the info, just hope I am remembering and applying it correctly.

    Good Luck

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    Re: Question about up-rezing

    Awesome! You learn something every day here at GetDPI.

    Thanks!
    Tim

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    Re: Question about up-rezing

    Minor correction to Charlie's post -- if the 20% over via smoother, back down via sharper doesn't work, try 10% increments up to 20% over using NORMAL Bicubic, then downsize to target via sharper.

    Note that if the image is marginal to begin with as you indicated, you'll want to do targeted edge sharpening at the 20% over stage. For this, I'd recommend high-pass filter sharpening with about a 2 to 4 pixel radius.
    Jack
    home: www.getdpi.com

    "Perfection is not attainable. But if we chase perfection, we can catch excellence."

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    Re: Question about up-rezing

    Thanks Jack. Marginal is right. If this works, it will be some kind of miracle. But hey, the client is always right (right?).

    Tim

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    Re: Question about up-rezing

    Another big thanks for the info. A perfect example of how helpful this place can be. I was under a deadline and even though I advised against using the image, the client insisted and gave me the service bureau's specs to meet. I was able to do that and the files are with them now. Hope it works out for them, but I can be comfortable that I did everything I could to make it happen.

    Cheers!
    Tim

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    Re: Question about up-rezing

    and yet another take on that...

    bicubic (either way "normal", "sharper" or "smoother") works the best when it has to interpolate 4 pixels out of 1 pixel... i.e. at 200% enlargement. Any other scaling leads to an arbitrary pixel count and the bicubic method is not very good at that.
    So... enlarge 200% than downsize to the desired dimensions (downscaling is not as ciritcal as upscaling... so here the arbitrary value works better).

    Depending on the motif you might try Alien Skin "Blow up 2". It is absolutley brilliant in avoiding aliasing artifacts. It rounds edges a little bit which is mostly not a problem but might be an issue if the motif contains a lot of very fine lines...

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    Re: Question about up-rezing

    Thank you thomas. I rarely do any up-sizing but have now realized the potential. Unfortunately, I wasn't able to experiment with actual prints. I'll have to do a bit more on my own to really see how well it works.

    Tim

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