TSB
screen printing => Newbie => Topic started by: blue moon on April 02, 2011, 01:24:19 PM
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RIP (raster image processor) is a program that provides several functions needed to generate the screenprinting films.
1. it converts the grayscale in the image to halftone dots. This allows the reproduction of photo type art to be printed with a screen.
here is an example:
(http://t-biznetwork.com/wp-content/uploads/2009/12/halftones1-web.jpg)
copyright scott fresner/t-biznetwork
2. It controls the amount of ink deposited on the film (for ink-jet printers). Most printers used for the film positive generation allow for different amount of ink to be deposited with each droplet. This function, on a basic level, compensates for different types of film and their ability to absorb the ink. More sophisticated programs will actually allow for compensation based on the halftone percentage (for example, depositing less ink in the middle range where the likelihood of dot gain is higher. Or if the films are not dark enough in the shadows, ink volume can be increased there without influencing the snaller dots)
3. Provides Post Script Language for the printers that are not compatible with it. Most of the InkJet printers are not equipped with a Post Script Language needed to interpret the halftone results to printhead commands. In this case, RIP software translates the percentage dots generated by conversion and it directs the printer (or in some cases the printhead directly) how to eject the ink.
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ooooh! Look at you! Mr. "can do" too. ;)
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I thought it was people put on headstones...
LIKE
R.I.P
Here lies someone... you know
dlac
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I wrote this article for Specialist Printing, the ESMA magazine in 2007.
http://www.ulano.com/ijf/whatdoesaripdo.htm
http://www.specialistprinting.com/index.htm
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I wrote this article for Specialist Printing, the ESMA magazine in 2007.
[url]http://www.ulano.com/ijf/whatdoesaripdo.htm[/url]
[url]http://www.specialistprinting.com/index.htm[/url]
Hey Richard, can we post that on here if we give Ulano the copyright credit and a link?
pierre
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I did post this on the Ulano site when I was their webmaster, but they have no rights at all.
The article is mine. I wrote it on my own time.
Use it anyway you wish, credit to me and mention Specialist Printing. I have many more pictures and a PDF of the actual article.
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Welcome Mr. G, good to see you around.
I'd like to add that RIPs support trapping.
They can also do some wonderful things like hybrid screening etc.
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I did post this on the Ulano site when I was their webmaster, but they have no rights at all.
The article is mine. Use it anyway you wish, credit to me and mention Specialist Printing. I have many more pictures and a PDF of the actual article.
Anything I worked on, or thought of, during my term of employment at your competitors became their property. Luckily for me that amounted to practically nothing ;)
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I think an interesting discussion, in addition to what a RIP does, would be to talk about when a commercial RIP becomes necessary for a shop. There are a lot of smaller shops out there printing 3 or 4 color designs with basic halftones that can use something like Ghostscript and have zero problems. I know Frog uses GS, as do I. At which point should someone start looking toward a commercial RIP?
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My twopence worth would be when the throughput justified it. I never think that it's reasonable to spend more on the RIP than your printer.
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I think an interesting discussion, in addition to what a RIP does, would be to talk about when a commercial RIP becomes necessary for a shop. There are a lot of smaller shops out there printing 3 or 4 color designs with basic halftones that can use something like Ghostscript and have zero problems. I know Frog uses GS, as do I. At which point should someone start looking toward a commercial RIP?
I've seen films from GS and when compared to FilmMaker films I'd say... today is the day to make the switch to a commercial RIP.
My thought is:
There are so many variables in screen printing, why not try to eliminate as many as possible ?
Waterproof film and a good RIP will just about eliminate film density/exposure issues.
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2. It controls the amount of ink deposited on the film (for ink-jet printers). Most printers used for the film positive generation allow for different amount of ink to be deposited with each droplet. This function, on a basic level, compensates for different types of film and their ability to absorb the ink. More sophisticated programs will actually allow for compensation based on the halftone percentage (for example, depositing less ink in the middle range where the likelihood of dot gain is higher. Or if the films are not dark enough in the shadows, ink volume can be increased there without influencing the snaller dots)
Your wrong on point 2. A "RIP" is a Raster Image Processor, constructs a "raster image". In a postscript rip which generates halftone dots, the function which varies the size of the dot is built into every postscript rip, not just the high end ones. This is true all the way back to postscript level 1.
Printing the raster image blacker on an inkjet printer is a function of the device driver. Most people who use ghostscript use gsview to generate a raster image, then use the standard windows device driver to output the film. The windows driver does not offer the option to print at double density, but does allows darker printing than the drivers default settings.
Features such as trapping and imposition are performed between the RIP process and the device driver output.
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My use for a screen printing RIP is to increase UV density of the transparent Epson black ink designed for photographs and control the final halftone size even with all that ink. This purpose for screen printing is unique.
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http://en.wikipedia.org/wiki/Raster_image_processor
A raster image processor (RIP) is a component used in a printing system which produces a raster image also known as a bitmap. The bitmap is then sent to a printing device for output. The input may be a page description in a high-level page description language such as PostScript, Portable Document Format, XPS or another bitmap of higher or lower resolution than the output device. In the latter case, the RIP applies either smoothing or interpolation algorithms to the input bitmap to generate the output bitmap.
Raster image processing is the process and the means of turning vector digital information such as a PostScript file into a high-resolution raster image.
So at the core of all RIPs is the above function. Processing image and page description information into a bitmap file that can be sent to the printer driver to be printed on an inkjet.
What sets apart commercial RIPs, epsecially those produced with screen printers in mind, is the way the RIP is implemented and enhanced. For example, I use Accurip - it loads as a system service on the computer so it is always on and ready like a printer driver is (they call it a driver-based RIP). Also, it can override the stock print driver and graphic application settings and do some cool stuff (multi black carts, locking screen angles and LPI, auto n-up, etc)
But yeah, at the core, a RIP is a RIP.
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If you use a Windows driver you will get rich-blacks composed of CMY&K. A RIP will use a monochrome black - just the black ink which has the highest uv density.
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No, my point wasn't that a rip was a rip, but that postscript is postscript.
Halftone calibration is a postscript thing, not a rip thing. Double density inkjet ink is a rip thing, not a postscript thing. A postscript rip all can do the calibration thing, but not necessarily the double density thing. By the definition of a RIP, a none postscript rip could do the double density thing.
Postscript, as defined by the "red book" from adobe, defines what postscript does and does not do. To a person who does not speak the postscript language, the line of what is postscript and what is a rip feature bend into mud, there actually is a hard and clean dividing line. Blue moon placed halftone calibration on the wrong side of that line.
As for printing using the windows driver, there is a very easy way to print with double UV density, at least on the epson 1400, just change the bitmap into a CMYK image and place a copy of the bitmap in both the black and yellow channels. For genuine epson ink, the yellow ink is nearly as opaque to UV light as the black. I've heard of people adding magenta and cyan, but in my testing, only the yellow is UV opaque. Printing 100% yellow plus 100% (K) black, the film will have a double UV opacity.
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2. It controls the amount of ink deposited on the film (for ink-jet printers). Most printers used for the film positive generation allow for different amount of ink to be deposited with each droplet. This function, on a basic level, compensates for different types of film and their ability to absorb the ink. More sophisticated programs will actually allow for compensation based on the halftone percentage (for example, depositing less ink in the middle range where the likelihood of dot gain is higher. Or if the films are not dark enough in the shadows, ink volume can be increased there without influencing the snaller dots)
Your wrong on point 2. A "RIP" is a Raster Image Processor, constructs a "raster image". In a postscript rip which generates halftone dots, the function which varies the size of the dot is built into every postscript rip, not just the high end ones. This is true all the way back to postscript level 1.
Printing the raster image blacker on an inkjet printer is a function of the device driver. Most people who use ghostscript use gsview to generate a raster image, then use the standard windows device driver to output the film. The windows driver does not offer the option to print at double density, but does allows darker printing than the drivers default settings.
Features such as trapping and imposition are performed between the RIP process and the device driver output.
the reality is that the RIP software available to the screenprinters provides the access the that functionality. In some cases, if I understand correctly, RIP will take over the control of the head end print directly bypassing the regular driver. So RIP can control the ink volume too . . .
In the end, we are talking about what a commercial RIP package will do for a screenprinter, so from that perspective, the description does not seem to be out of order.
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What is "out of order", is that there is actually a hard division line between what in inherent to postscript and what is product specific.
It would be like trying to talk about the powertrain of a car, without dividing the powertrain into the engine, transmission, drive shaft and rear end. The engine is postscript, where the double hit of black is a gear in the transmission and has nothing to do with the engine.
Just as ford and chevy have differences, the basic function of the engine remains the same. LPI and calibrations are like the air fuel mixture, these variables are common to all engines.
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What is "out of order", is that there is actually a hard division line between what in inherent to postscript and what is product specific.
It would be like trying to talk about the powertrain of a car, without dividing the powertrain into the engine, transmission, drive shaft and rear end. The engine is postscript, where the double hit of black is a gear in the transmission and has nothing to do with the engine.
Just as ford and chevy have differences, the basic function of the engine remains the same. LPI and calibrations are like the air fuel mixture, these variables are common to all engines.
All true, I like your example it would give a new person some idea of how this works
Some things people miss (or misunderstand) about Ink Jet printers and a RIP in addition to your points (from my class and several articles)...
A RIP (Raster Image Processor) will provide the following when used to drive an epson printer:
1.) Allows the use of the separator sub-programs in a professional way without resorting to time wasting silly ?work arrounds? most professional art separators abandoned 20 years ago.
2.) Allows printing of adjustable dots (halftones - as you stated under the ?supervision? of the post-script producing program like Illustrator).
3.) Makes the D-Max areas much darker by allowing the RIP to take control of the peizo print heads and pump more ink onto the emulsion layer of the receiver film. (This works best when the inks in the printer are converted to a more UV blocking substance, for example this inexpensive product - http://store.inkjetcarts.us/screen-positive-black-hybrid-ink-p4487.aspx (http://store.inkjetcarts.us/screen-positive-black-hybrid-ink-p4487.aspx) - a hybrid Ink that produces much higher quality results than the poor preforming epson factory inks)
4.) Helps printer produce positives in registration - this is the issue most missed by almost everyone, a RIP will control the placement of the image on the film in much, much, much, more accurate registration than any standard driver is capable of producing.
5.) Makes a much higher quality product that is faster to produce and place into use because it allows the artist to print positives using the high quality, convenient, and professional level print sub commands.
Faster is more profitable, it never ceases to amaze me how some in the industry will tart up every feature of retensionable frames, impossible fantasy numbers for ROI on an automatic press, running slave like shops squeezing everything possible out of harried workers and then promote some of the most primitive, backwards, pathetic, silly, time wasteful, and simply ignorant art production methods. (Thankfully this has not shown up on the boards here.)
The RIP Richard used to work with with Ulano is featured on this page:
http://www.ulano.com/ijf/PowerRIPFAQ.htm (http://www.ulano.com/ijf/PowerRIPFAQ.htm)
A fine product that works well with the inexpensive ink listed above.
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and then promote some of the most primitive, backwards, pathetic, silly, time wasteful, and simply ignorant art production methods.
Speaking of, someone mentioned their rip being able to add a trap. I waste a crap ton of film (and time) because I don't understand how to set the overprinting correctly in illustrator it seems. I build clean files and clean up my clients files and prefer butt registration on most jobs but, there's always a few that need the wiggle room. Surely I'll get better at this as I go but find myself just going to butt reg or using a sep method that falls into the above description.
To be able to have your file in all spot color and add that trap to the spot colors of your choosing doesn't sound too far-fetched I guess. I would imagine the rip would just surround each pixel without a neighbor on all four sides with a pixel or something simple like that. For printer's that don't have a ton of gain this would be super helpful in decreasing setups and downtime on press, too add a very thin trap to your positives.
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I've thought about adding trap to my version of ghostscript, but the tricky part of automatic trapping, is the lack of a user interface to define the intent of the trap.
Many people setup layers to act as separation, by switching on and off different layers and printing one piece of film. Somehow a rip needs to know what jobs will combine into a single image. Then the rip needs to know which layers of ink to spread or choke and which don't. For example, a red ink printing on white, should the red spread or should the white choke?
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I've thought about adding trap to my version of ghostscript, but the tricky part of automatic trapping, is the lack of a user interface to define the intent of the trap.
Many people setup layers to act as separation, by switching on and off different layers and printing one piece of film. Somehow a rip needs to know what jobs will combine into a single image. Then the rip needs to know which layers of ink to spread or choke and which don't. For example, a red ink printing on white, should the red spread or should the white choke?
Because trapping causes a higher likelihood of additional flashes I try not to, trap that is, I and others do use a choke quite often - I would be looking into an automatic choke function, do any of the lower cost rips offer this?
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I would like to add a side note to this, not all RIPs are screen printing oriented. Most importantly, not all RIPs will do halftone seperations. When I was searching for my wide format printer, I was looking for something that would do graphics well, not produce films so when I was looking for printers, I was looking more for a prepress oriented rip than a screenprinting rip. I ended up with an epson 10600 that came with a bestcolor rip and stand alone color management software. While there was an option offered by bestcolor (now efi) for separations, it added greatly to the cost. No matter, color matching was much more important at the time.
What it does do for me is allow ink density adjustments, nesting and much higher quality line and dot resolution over the oem drivers. As I get further into this business, I will look into a screenprinting rip. But for now, it is getting me nice looking films.
The upshot of this is that if you are looking for a used inkjet for films, look for one with a RIP. Usually they aren't much more expensive than those without. Preferably with a screenprinting specific rip, but any rip is better than the oem drivers. Of course research is a good idea on unfamiliar RIPs.
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I would like to add a side note to this, not all RIPs are screen printing oriented. Most importantly, not all RIPs will do halftone separations.
A very good point, and correct as the “color” RIPs often cannot produce positives for our needs.
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True, I can't speak for all pre press style RIPs, but I got lucky on this one. It looks like no one made a film RIP for the 10600. Even if they did, it would be pretty outrageously priced due to the size of the printer, even though I don't print on anything larger than 24" film for positives. Can anyone speak to the reasoning behind bigger printer= bigger price?