Color Trapping

[inphoenix]

CD9 both updates, when I choose color seps the Always Overprint Black is greyed out. I have very close registration for t-shirt and printer has problems with this. Background is black and I need the knockouts so printing diff levels won't work with this one. Any suggestions?

Marie

[Not Ziggy]

Marie, I mis-read something at HP's site. The replacement for the 6MP is the 2100M, not the SE. The good news is that the resolution has gone up from 600 on the 6MP to 1200 on the 2100M. The bad news is that they now qualify their PostScript as being "emulated" rather than "true." (You can still read the specs there on the discontinued 6MP.)

After searching numerous other sites, I have yet to find any other manufacturer selling "true" PostScript in anything less than an imagesetter.

If you have either a computer superstore or a Mac store in the area that sells an HP 2100M, you can probably take a PostScript file in there generated by the Corel "Device Independent File" option and see if it yields varied lpi. Keep the fonts simple.

I've written to Adobe about this issue and I'll post here whatever they tell me.

[inphoenix]

CD9 both updates, when I choose color seps the Always Overprint Black is greyed out. I have very close registration for t-shirt and printer has problems with this. Background is black and I need the knockouts so printing diff levels won't work with this one. Any suggestions?

Marie

[Not Ziggy]

The feature you're trying to use is only available when printing to PostScript printers (as is overprinting on the color level). However, you can still cause overprinting at the object level. (Right-click on the object and select "Overprint Fill" or "Overprint Outline.") Of course, this can take a long time on a complex document.

Or, you can provide a color-separated PostScript print file for outputting at your screen printer or elsewhere. Select "Device Independent PostScript File" from the list of printers and the "Always overprint black" button will be available.

[Larry Elliott]

Thanks Ziggy for the confirmation on what I had become to take for granted that the Epson 3000 CPS IS NOT a true post script machine. The 'tech' at Epson argued with me that it was but I was just trying to doing something with it that a 'desk top' printer was uncapable of. I've been well pleased with the output of the printer in all other ways, the high res color on good paper rivals that of offset. According to Epson, 'the use of non-Epson inks WILL CAUSE CLOGGING of the heads' and the heads will have to be replaced or sent to factory for repair, B.S., I fell for that while the printer was still under warranty and paid around $60 a cart for their proprietary inks. I've since used 'compatible' inks and have not had a problem and have saved several dollars! Lots of diff when you compare $240 for a set of Epson inks to $80 for the same stuff in a 'plain wrapper'. Makes me wonder if I'll ever buy another Epson product, their tech support is not technical, their ad hype is more like lying and their consumables are WAY over priced.

Larry Elliott...

[inphoenix]

Ziggy,
You are so wonderful to spend so much time helping me and I feel like such a blob...
I understand the difference between lpi and dpi now but do not understand how this is affecting what I'm trying to accomplish. I was taking a 'shot' at adjusting the 'dot' lpi in the postscript options of a fill and it didn't work at all for me.
My main problem is I'm trying to print a hard copy of a color separation that requires overprinting the black outline. The t-shirt screenprinter has a very old time shop and does not use computers, only hard copy to burn his screens for actual printing. They are complaing that the resolution is too fine for shaded areas (anything less than 100% black) and could I make larger 'dots' for them. Now I know their 'dots' are not what you were talking about in the halftones. I guess I'll not be able to accomplish the required output for them. This is so frustrating. My mythical Ferrari is NO GOOD for me. What a bummer.

if the 'cells' of lpi is less then why don't I see a difference on the printed output? Or have I lost it again? LOL

Marie

[Not Ziggy]

(As a moderator in this forum I'm becoming an expert in the strangest things.)

Marie, I'm sorry to have to tell you this, but the HP 4500 is NOT a PostScript printer. (I feel like I'm breaking the news to people that there is no Santa Claus.) Instead it is the same thing that Elliott is wrestling with, which is a non-PostScript printer which comes with "PostScript emulation software" which is imperfect, at best. To quote from hp.com:

"The HP Color LaserJet 4500 Family printer will not recognize or accept custom LPI settings. The firmware does not allow for custom LPI/halftone commands. This constraint allows customers to get the best possible print quality in as many different printing scenarios as possible."

In other words, this is a printer that is dedicated to giving you the highest possible quality photographs and it will NOT let you interfere with its divine destiny by lowering the lpi. Obviously, it's rather EVIL on their part to give you places to change these settings and then disregard them, isn't it?

I'm afraid this boils down to the following: If people clammor for a six-legged dog, someone will find a way to manufacture and sell them one, no matter how lousy a pet it turns out to be.

And in this respect, I would answer Elliott's disparagement of Epson by suggesting that HP is swindling people in the exact same way, but doing a rather classier job of helping people feel good about it.

(Did anyone say, Macintosh?)

[Not Ziggy]

Please look at your last post: You say, "I tried the lpi thingy and took it down to the minimum and still prints out in 600 dpi." In other words, you adjusted the lpi and you're upset that the dpi didn't change. Why should it? It's as if you changed the idle speed on the engine of your mythical Ferrari and are shocked that the number of tires stayed the same!

The core of your confusion lies in the unfortunate fact that discussions of lpi often use the word "dot" to describe those 60 dark blobs in each inch at 60 lpi. (I just checked in the PhotoPaint 9 manual, and they do it in there.)

In a graphic design class, those blobs are not called dots. They're called "half tone cells" and they are very different from the microscopic dots involved in the "dots per inch" measurement. A half tone cell is actually a REGION visable under a loupe in which a cetain number of microscopic dpi-type dots live.

For instance, on a printer printing at 600 dpi and 85 lpi, there will be 600/85=7 dpi-type dots living in each cell horizontally and 7 vertically for a total of 7x7=49 dpi-type dots in the entire cell.

When you look at the array of blobs in a half-tone image, you are actually looking at an array of these cells. A large blob means a large number of microscopic dots are turned on in that cell. (For 50% black in the example above, about 25 of the 49 microscopic dots would be turned on.) A small blob means a small number of microscopic dots are turned on. If no microscopic dots at all are turned on, the cell is white. If all the microscopic dots are turned on in a cell, then that cell is pure black.

Are you beginning to understand? You know that a halftone consists of little spots. But you apparently did NOT know that those spots are THEMSELVES composed of even tinier spots! "Lines per inch" specifies the larger spots, while "dots per inch" specifies the much smaller spots inside them.

Notice how incredibly confusing this whole issue becomes if one starts to use the word "dot" to indicate BOTH the microscopic dpi-type dots and ALSO the much larger half tone cells. It is for this reason that you are confusing dpi (a measure of tiny microscopic dots of which you, Marie, shold always want as many as you can possibly get) and lpi (a measure of the much larger half tone cells of which you want only 60 in each inch on a typical tee shirt, but you want 133 if printing on glossy card stock).

Marie, I have invested quite a bit of time in trying to explain this because this is a very widespread misunderstanding. You are certainly not the only person (or the only visitor to this forum) who suffers from the sort of incredibly unprofessional drivel contained in such documents as Corel's PhotoPaint 9 User Manual.

Indeed, you are to be commended for keeping your cool as well as you have done.

Now, please, so that I won't feel that I've wasted my time, write back and tell me that you understand that lpi and dpi measure two different things, so that it is quite possible for a printed document to have BOTH 1200 dpi AND 60 lpi.

Your screen printer needs you to accomplish 60 lpi, not 60 dpi. I will be happy to help you accomplish 60 lpi, but you will never accomplish 60 dpi and there is no reason why you would want to. It would be like trying to drive on three wheels.

[This message was edited by Ziggy on October 16, 2000 at 08:05 PM.]

[goran]

Marie - maybe a small stone for your/our PS emulation mosaic... I have HP 5000 N for about a year now. It has emulation of PS also and is not able to print at different lpi's - unless I turn off "enhanced" option under greyscale menu (Printer/properties.../). With that option turned off, my HP can print at all lpi's I want, despite PS emulator. This emulator caused big price drop for "PS" (...) printers at HP - Adobe charge about 1000$ for their Postscript rights on every printers sold - so I've heard. My A3+/1200 dpi printer cost me about 2000$ and is well worth it. Do you have that option present in your's printer settings too?
goran

[Not Ziggy]

Adobe's response so far is to send me several tech papers. One of them includes the following: "If you are having problems printing to a PostScript-emulation device (e.g., LaserMaster printer, LexMark printer, or newer HP LaserJet black-and-white printers)..."

Notice the use of the word "newer." I think my theory is correct that HP as a company has lost its "true PostScript" compatibility for some strange political reason and should henceforth be stripped of its formerly royal status among graphics professionals.

The question remains: Which other companies, if any, are still worthy of our attention? Since we have two 1200 dpi tabloid-size Xante Accel-A-Writer 8300 printers here that are discontinued but work flawlessly with all sorts of software coming out of several different operating systems, I thought I'd visit their site.

Marie, if you've got $2000, I've got a solution to your problem: The latest version of the 8300 uses true Adobe PostScript and I can highly recommend it, if you can afford it. It's the Accel-A-Writer 3N and it's available at microwarehouse.com. (Or, there's a 600 dpi version for $300 less.)

And I'll keep looking.

(If anyone else out there is happily using a printer with true Adobe PostScript, we would all love to hear from you.)