large format printers and RIP

Discussion in 'Digital SLR' started by Steve Franklin, Jun 9, 2005.

  1. Hi all...

    Can anyone explain to me what a RIP is and why you need one on a large
    format printer?

    From what I gather it's Raster Image Processor and it sounds like it's used
    to handle picture files. What I can't work out I guess is why they are so
    expensive and why it just doesn't come standard with the printer.

    By large format by the way I mean those large, roll fed machines that do
    huge prints...

    anyone? anyone? Spicoli?
    Steve Franklin, Jun 9, 2005
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  2. Steve Franklin

    Paul Furman Guest

    Here's my understanding.

    They simplify the process of color profiling & include various custom
    tuned paper profiles. That part is basically a luxury, it can be done
    manually if you are careful & assemble all the various components perfectly.

    They have neato features for batching large jobs & getting margins &
    such just perfect, which is essential for commercial big jobs to get it
    right every time quickly without a lot of hand holding & make a profit.
    Paul Furman, Jun 9, 2005
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  3. Steve Franklin

    Bubbabob Guest

    If you want to look into a RIP that's reasonably priced, look into the
    QTR RIP. It's shareware and a tremendous bargain.
    Bubbabob, Jun 9, 2005
  4. Steve Franklin

    Sizer Guest

    First of all, large format printers are dumb as stumps. You basically send
    down the bitmap line by line, ink cartridge by ink cartridge, dot by dot.
    Though some HPs do handle postscript (because they have a built in RIP).
    RIP = Raster Image Processor, which basically means taking your source
    file which might be vector (postscript, illustrator) or raster and then
    turning it into the raster for the output.

    Okay now, imagine you're doing a 54 x 60 print. 600 dpi. 6 colors. 1 bit
    per printer pixel. That's 600*600*54*60*6/8 = 879 megabytes of final data
    you're slinging around PLUS 4.7 gigabytes of intermediate data for the
    scaled up CMYK image. If your printer is 1200 dpi (as many are), multiply
    all those numbers by four. Some printers do 8 colors, so multiply by 4/3.
    Any way you look at it there's a hell of a lot of data being thrown around

    It's nice to have this work offloaded on a dedicated machine because it's
    built for it and the RIP is built so it doesn't hold all this stuff in
    memory at once - it processes in bands. And of course you get a lot of
    control over the output.
    Sizer, Jun 9, 2005
  5. Modern wide format printers do not need to have the image rasterised before
    accepting data. The concept of a RIP is that you send your printer Industry
    standard "Postscript" files and the RIP processes these files into data the
    printer can recognize and so your poster is printed.

    That was in the bad old days. Today, machines that produce six feet wide
    photographs, with durable, 6 colour ink process not only have common
    Windows/ Mac drivers but contain their own hard drive and basically a
    transparent RIP you don't need to bother with.

    If you are going to purchase one of these monster, Inkjet printers ...the
    new Epson range just released use a newly developed ink dubbed "K3" which
    supposedly has a 200 year print life. How you discover if this is true, is
    the start a new superannuation fund which matures in 2205 so you can come
    back from your holiday with God and closely examine the print with a 16x
    loupe you hide away with it before you die.

    For the rest of us... The 75 year life of HP, new dye based inks is more
    than sufficient. I doubt anyone with enough time to write or read newsgroups
    need be concerned with such archival lasting ability as Epson claim. My own
    accelerated testing process is much more highly refined than the Wilhelm
    institutes. I make a print and put it in a special glass case I have called
    a 'window' which faces a direction able to capture the sun all day. (sorry,
    you'll have to guess which direction).

    After a suitable time, I compare the print with it's duplicate I made and
    kept in a dark place free from formaldehyde and other household agents know
    to destroy inkjet prints in a matter of weeks. My comparison technique is
    surely ancient, compared to those developed by Wilhelm with all the cash
    Epson give him to produce the findings they want but none the less, my
    densometer has served me well for 15 years and it tells me by how much a
    picture has faded under real life conditions.

    How fast Inkjet prints degrade when exposed to sunlight is one measurement I
    How fast Inkjet prints degrade when exposed to a spot light is another.
    Finally how fast Inkjet prints degrade when pinned on the wall of a high
    traffic area.

    Oddly, my conclusions about the life of an inkjet print are in conflict with
    those from the Wilhelm Institute. Maybe if I can convince Epson to fund my
    lab, I too might pluck up enough courage to make outlandish predictions of
    how long a print will last? The best I can do without printer manufactures
    funding is about 8% of Wilhelm's claims... Funny thing that...

    Solvent ink printers are the only ones able to make posters suitable for
    long term display. The down side is you have to continually treat them like
    a brush, clean them and generally use them all the time or they will behave
    like an Inkjet printer with paint in the lines... Which is what they are!

    I feel so much better now.
    Ryadias_Kiosk, Jun 9, 2005
  6. Steve Franklin

    Andrew Haley Guest

    I'm going to ignore all the convenience and workflow issues and
    concentrate on the quality issue.

    Large format printers generally come with a driver that takes RGB
    data. However, the printers are physically CMYK devices, and they
    have to convert RGB to CMYK in order to do the printing. So, in the
    printer driver there is some logic to do that. Accurate RGB->CMYK
    conversion is, to say the least, a very delicate operation and to get
    the best results you need a precisely calibrated printer. The RGB
    drivers that are supplied by the printer manufacturers assume
    "typical" inks and papers when they do the RGB->CMYK conversion.

    A RIP sends CMYK data to the printer, not RGB data. As a consequence
    of this, the RGB->CMYK conversion is under the control of the user,
    and can be controlled by precise measurements of the particular inks
    and paper being used. Also, the user can adjust the black generation;
    that is to say, the density at which black ink is used rather than a
    mixture of colours.

    An ideal workflow involves printing a test chart and measuring it with
    a spectrometer, which tells you the reflectance of each individual
    ink and the way that the inks blend on the paper you're using. A
    "printer profile" is generated from these measurements, and this
    accurately characterizes the process. Then, the RIP converts your RGB
    data into CMYK data under the control of that profile. This is the
    most accurate way to print in colour.

    As a "second best" solution, it is possible instead to generate a
    profile of a printer entirely from RGB data rather than from CMYK
    data. That is, you send RGB data to the printer and generate a
    profile by measuring the test chart. This profile can be used to
    adjust RGB data sent to the printer driver and thereby generate
    reasonably accurate colour. However, this isn't ideal because the
    critical RGB->CMYK conversion is not based on the measurements of the
    particular inks and paper you're using on your printer, but on a
    "typical" sample. Custom RGB printer profiles can produce very good
    results, however, and certainly good enough to satisfy all but the
    most critical eye.

    Andrew Haley, Jun 10, 2005
  7. ------------------------------------
    In addition to this lucid description I would like to point out that the
    latest printer/plotters from HP have their own inbuilt RIP and spectrometer
    and are capable of generating colour profiles on the fly. If you use a paper
    source with no profile, simply make a test plot which the printer analyses
    and adjusts itself for, then start printing.

    [email protected], Jun 10, 2005
  8. Steve Franklin

    Andrew Haley Guest

    It's not a spectrometer, is it? I thought it was only a colorimeter.
    Also, AFAIK people still use canned ICC profiles on these printers,
    with automatic closed-loop color calibration at the back end after

    Andrew Haley, Jun 14, 2005
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