What kind of PostScript RIP server can reproduce all the original colors of your digital image?

A PostScript RIP server takes care of processing the raster images (hence its name, Raster Image Processor). In effect the hardware Postscript RIP is a separate computer (a server) which dedicates itself to taking your graphics image and placing each color dot in its proper position onto the paper. The RIP is associated with a large format color printer.

The computer sent the TIF file (or other comparable file) to the RIP server via Ethernet cable along with the layout (if any, such as Adobe InDesign, Adobe PageMaker, or QuarkXpress). This takes about 1 or 2 minutes (especially if you have 100Base-T speed (Fast) Ethernet or Gigabit Ethernet).

The PostScript RIP server takes this load from your Mac or PC and lets you return to using the Mac or PC to do other work. The RIP takes care of processing the millions of bits of information in your large format color print. The EFI Fiery RIP is fast enough if the files are small, say around 150 MB. If the files are at the maximum which a 600+ wide format printer can handle, then the Fiery is rather slow as it grinds away at all that excessive file size (225 MB is the largest file the system can handle to produce a 600 dpi image on the printer). Nice thing about a Hewlett-Packard DesignJet printers is that you can send them 120 to 150 dpi in your original file and achieve the full 600 dpi photo-realistic quality that this HP printer is capable of.

If you want to get even faster RIP times, the Hewlett-Packard printer is good enough to handle a JPEGed file; in other words, JPEG your file and then send it to RIP and print. We prefer, however, never to compress any of our files.

How much dpi (in your print) does your 600 dpi printer really want, or need? These crucial tidbits of information never seem to be in the instruction or operating manual.

John Nagel, Director of the Center for Advanced Imaging (St Louis, MO) said that 120 dpi was more than enough for his HP 2500 and 3500. He said that a normal viewer did not notice any improvement in quality if you used a higher dpi. Our tests with an HP 2800 demonstrate that 225 is about a safe maximum. 250 dpi and above cause indigestion to most PostScript RIPs and cannot be interpreted correctly; to much DPI causes distortion of the image. An experienced technical expert at HP large format headquarters in Barcelona, Spain said that 150 dpi was more than enough.

I am always curious how much dpi you can feed a printer before it gets indigestion. With the Encad NovaJetPro files over 180 dpi began to give the system indigestion. This is not really a fault of Encad, it is more likely a restriction of PostScript. Anyway, "indigestion" means that the RIP selects about 33% of the image, eliminates the other 66% and then stretches the selected 33% and fills the entire space with this stretched (and hence distorted) image. With the HP when I raised the dpi to over 275 I reached the point where the system could no longer handle it. At 250 dpi the system was still overloaded, so to be safe I don't try any prints over 225 dpi.

Below is an Encad wide format print, the complete rollout (except for a band along top and bottom which we cropped to keep download time down). Other pages show a close-up of the enthroned ruler and a close-up of the kneeling attendant. We also use an EFI Fiery RIP with this Encad printer. Recently, however, we abandoned the Encad and upgraded to the Hewlett-Packard DesignJet series of large format printers. We happen to have the HP 2800 CP; the quality is the same on the whole CP series, 2000 and 3000 (use an outside RIP); 2500 and 3500 (have their own interior HP RIP), and 3800, the 54" version with the EFI Fiery RIP.

What media do we use in these wide format printer evaluations? Photo paper from Rexam Image Products, rexamimageproducts.com

 

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All reports by Dr. Nicholas Hellmuth

 

UPDATED: July 11, 2001