What is a raster driver?

Discussion in 'Large Format Inkjet Printers' started by tonymaclennan, Nov 25, 2010.

  1. tonymaclennan

    tonymaclennan Member

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    In my quest to resolve my colour profile issue I am trying to learn is much as possible about how it all works from computer to printer to paper.

    Can't find anything on Google.

    Is a raster driver different to a standard driver? Or are they the same?

    Thanks
     
  2. RichardK

    RichardK Senior Member

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    I'm really tempted to say... Bob Marley... chauffeur! But instead I'll try and point you the right way :)

    Colour management is what you need to be googling. Raster driver would be a RIP (raster image processor) a bit of software that interprets PostScript output from page layout packages such as InDesign/Quark Xpress.

    These days most workflow is PDF based but it does rather depend on the kit you have. I would suggest you list your equipment and software (versions too).
     
  3. tonymaclennan

    tonymaclennan Member

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    lol :)

    I cannot seem to find a resolution for my colour management issue so now doing everything I can to learn everything about computer-->printer-->paper.

    Is a raster driver anything significantly different to a normal driver?

    I am using Photoshop CS2 and also have installed Photoshop 7, Macromedia, CorelDraw. Working with Wndows 7 64bit. Also tried is from Windows XP Pro and Windows Vista.
     

  4. RichardK

    RichardK Senior Member

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    Right...I'll give it my best shot.
    I'm guessing you're trying to print an RGB file and find the print not matching? Well you see you're trying to match what you see on screen (which if uncalibrated won't show the right colours anyway) with a physical printout. Out of gamut colours will often print far duller than what you expect.

    Why...OK some physics...
    RGB and other variants sRGB etc are renditions on a colour monitor, ie light transmission (like transparencies). Whereas a printout is a rendition where you view light relected through the inks bouncing off the base material and coming back through. The two are effectively poles apart.

    What can you do...well depending on kit/software and your colour perception (after all colour is subjective...what looks blue to one person can easily look purple to another) quite a bit.

    Is you monitor colour calibrated? If not then that's your first step. Calibrate a PC Monitor

    After calibrating the monitor open the affected file in PhotoShop (doesn't matter which version).
    Go to the View menu and select Proof Set up > Working CMYK (this will show you the result you can expect from an RGB file when converted to CMYK.
    This task is normally undertaken by the RIP and how the conversion takes place is pretty much dependent on how the RIP is set up.
    Next go to View > Gamut Warning - if you see a lot of grey suddenly appear (usually bright blues/greens/oranges) this means that those areas will undergo a colour shift.
    So next step is to leave the file setup with Proof Set up > Working CMYK and adjust colours until you see a closer approximation to the desired result.
    Then go to Image>Mode and choose CMYK save the file as 'file name CMYK' so you still have the original untouched.

    use PShops print function and try a printout with Printer Handles colour/Relative Colorimetric.

    Let me know how it goes.

    Now as for differences between raster and 'ordinary' printer drivers..

    RIPs tend to be for highend output, litho plates/film etc or proofing colours accurately. The standard driver that comes with your printer might be a little faster but colour accuracy comes from a good quality software RIP eg Oris/Harlequin/Apogee/EFI etc. NOT cheap but very effective and 'tuneable'.

    The last items in the chain are inks and paper. If you're using compatible or non-standard inks expect colour issues and possible blockage to the inkjet head.
    Paper - it's amazing how a change of paper will affect output rendition. In fact there's a good living to be made from calibrating printers to a specific paper but then you need a good spectrophotometer as well as a RIP that can take such readings and adjust itself accordingly.

    We run Apple LCD monitors (around 6 yrs old) Adobe Creative Suite 4 (PShop/Illustrator/Indesign/Bridge) which allows colour to be synchronised between those applications (a spot colour conversion from an old copy of say Quark or Corel will bear no relation to todays CMYK breakdowns and inks). Our proofer is an Epson 7800 driven by a EFI ColorProof XF RIP.

    Hope that helps and gets you on the road to successful output.
     
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