What is a RIP anyway?

[yorkie]

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.

[blue moon]

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.   

[yorkie]

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.

[DouglasGrigar]

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 - 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

A fine product that works well with the inexpensive ink listed above.

[ZooCity]

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.

[yorkie]

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?

[DouglasGrigar]

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?

[StuJohnston]

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.

[DouglasGrigar]

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.

[StuJohnston]

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?