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DPI for highest quality?

Discussion in 'Printing & Print Design Forum:' started by PrintMania, Aug 24, 2016.

  1. PrintMania

    PrintMania New Member

    Imagine a simple PDF file with a bit of text in it. If the text is real text, ie. vector graphics, it comes out looking very good. If I rasterize the same text (or any vector graphics) at the same resolution as the printer then it still doesn't look as crisp as the vector graphics.

    I would have thought rasterizing a vector to the same resolution as a printer would give vector quality. Is this not this case and is there something that I'm missing?
  2. Paul Murray

    Paul Murray Moderator Staff Member

    Vector will always look crisper because it's calculated through maths and doesn't have a resolution as such (if just gets scaled up). When you rasterise you're converting it to pixels, which are just squares, hence the lack of 'crispness'. If you need none-editable text in your PDF just outline it instead of rasterising it.
  3. PrintMania

    PrintMania New Member

    I still don't understand it. If you print a vector it will be rasterized before the droplets of ink are placed won't they? If I remember correctly you could still see pixels on the printed vector but it was just smaller and harder to see.
  4. hankscorpio

    hankscorpio Moderator Staff Member

    When you have vectors such as text or logos etc. what happens is that the RIP (raster image processors) converts it to raster just before printing, and it converts it to a much higher PPI than what you may do.

    If you take a vector text and convert it to a bitmap, say 300 ppi - that won't be enough to render the text in good quality. You'd have to use 1200 ppi or even 2400 ppi.

    If you rasterised your vector and placed it in a file, then when making the PDF there is an option to downsample raster images to a certain amount of DPI. Here you may find that your 1200ppi rasterised vector is now being downsampled to 300 DPI - so it would be best to choose no downsampling.

    Where vector is a huge advantage prior to RIPing is that the RIP does the conversion on output, it uses the best settings for that particular printer/platesetter/film setter/ to produce the vector in the highest quality.

    Vectors are also scalable to any size imaginable. Use that vector on a business card, or on a building wrap. However, if you rasterised the vector for the business card, you couldn't possibly scale that to the size of a building without causing major pixelation.

    In short - the RIP manages the conversion to raster, and uses the best setting. You just need to place a Vector and leave the math to the printing device.

    My advice for text is to if you have to rasterise it, make it at least 1200 ppi, And don't downsample it.
  5. PrintMania

    PrintMania New Member

    What I really want to know is the best settings for my particular printer. I know the ppi and I have matched the ppi with the dpi, but the vector still looks like a higher resolution. Let me give an example...

    If you print a vector at 300ppi and you rasterise the same vector at 300dpi how would the results differ? I'm finding that the vector is still a higher resolution.
  6. hankscorpio

    hankscorpio Moderator Staff Member

    It depends on your printing device.

    You never have a print vector at 300 ppi - vectors don't have PPI.

    If you rasterise the vector to 300 ppi then it will depend on what size it's placed at.

    Placed 100% it prints 300DPI.

    If you scale it to 1000% then it prints at 30DPI.

    If you scaled it to 10% then it prints at 3000DPI (or whatever the maximum resolution of the RIP).
    @GCarlD likes this.
  7. @GCarlD

    @GCarlD Well-Known Member

    It sounds like you may be getting confused as to the difference between PPI, DPI and Vector: Remember as Paul explained above, vectors are not made up of pixels, therefore as Hank says they do not have PPI (Pixels Per Inch). When you rasterize the vector, it converts it into pixels; now you are dealing with PPI. What it prints out at would be DPI (Dots Per Inch).

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