Note on archived topics.
11-09-2010 01:52 PM
I sure hope you can answer and/or solve my dilemma, because ultimately you sound you might have the knowledge!
I recently bought an HP LaserJet P1505 printer.
I am a Desktop Publisher and Graphic Artist and use QuarkXpress and most all Adobe products.
The P1505 was a replacement for my old Xante Accelawriter 8200 postscript printer which quit on me.
On my Xante, in QuarkXpress I could send a job to the printer and specify color separations and screen frequency.
However when I send to the P1505, the options for separations, screen frequency, etc., are dimmed and therefore not accessible! I have read because the P1505 is not a postscript printer, those selections are not possible.
If the P1505 is PDL and PDL is like Postscript which means "printer description language", why can I not access those options?
I am using an Apple MacPro1,1 Intel running OS10.4.11 (also have OS10.6 on different hard drive, but options for separations and screen frequency are not available there either).
I have read and tried everything under the sun I can find, but no luck! Please help and answer this.
11-09-2010 03:41 PM
You must have read that long article I wrote about print drivers. Perhaps I should look at that again and make sure I defined all my terms. A "Page Description Language" or PDL is fairly generic term applied to the command set used to tell a printer what to print. PostScript and PCL are examples of Page Description Languages just like English, French and Spanish are examples of spoken languages. Even JPEG and PDF can be PDLs. But as with any language, some are more expressive than others. Your printer must understand the language being sent to it or all it hears/prints is gibberish. In the end, printers output an grid of pixels, A printer that understands a JPEG file is given the exact grid of pixels to print. A printer that understands a PostScript file is given instructions on how to construct the grid of pixels to print. The difference is that PostScript is actually a programming language and can execute commands other than "print this".
The P1505 doesn't know how to interpret a JPEG file or a PostScript file. It has its own language that the driver uses to have it print pages. But it is much more like JPEG than PostScript in that your Mac constructs the grid of pixels to print before the it is sent to the printer, rather than being told HOW to generate the grid of pixels as is done in a PostScript printer.
From here I have to tell you I have only a passing familiarity with the applications you mention. I work more in XCode than XPress. What follows is based on only limited experience with these apps.
The applications you are using like PostScript so much that in many cases they generate their own PostScript code (when using a Postscript printer) because they think they can do it better than the driver can. One thing they get from this is the ability to instruct the PostScript printer to do interesting things like color separations. But unless your printer can handle PostScript you don't get the feature.
That said, I do have something for you to try. I have little confidence that it will work, but there is no harm in trying.
First you need to figure out a way to get the application to create a PostScript file with the options you want turned on. Since these apps frequently have their own print dialog it may be right there. If not you can try Apple's (Get to the Apple Print Dialog, click PDF and choose "Save as PostScript...") but using Apple's method makes it less likely the app will include the special commands for color separations.
To do this you may need to create a print queue (aka "Printer" as shown in the "Print & Fax" panel of System Preferences) for a Postscript printer. I know, you don't have one. But you can add another queue for your P1505. Name it something like "Phony PS Printer". When it chooses the PPD* under "Print Using:" choose "Select Printer Software...". Pick any color PostScript printer. Since you can't usually tell which are PostScript and which are not I'll suggest an "Apple Color LaserWriter 12/660 PS v2014.108" since you won't have to scroll to find it. You will be told you already have a queue for this printer, tell it to continue anyway.
NOTE: If you actually print using this queue you may waste a lot of paper by printing gibberish!!!
If you are successful in getting a PostScript file the next thing to do is open it in Preview. Some find it surprising that Preview can open PostScript files, but it can. If the color separation commands have been added to the file in the application, and if Preview interprets them correctly what you see in Preview will be the color separation plates you are hoping for. If so, you can print them to your P1505 using Preview (use the original print queue and not the phony one!), and if not I am afraid you need a Postscript printer.
Good luck, and please post what you learn both for me and the benefit of others.
*PPD is an acronym for PostScript Printer Description. Originally it was just that, but on today's Macs ALL printers need a PPD whether they understand PostScript or not. A PPD file stores a list of features the printer implements and instructions (for the driver) on how to use those features. This would include, but is not limited to, things like supported paper sizes and whether the printer can print on both sides.
01-11-2011 12:42 PM
I not sure how many people have actually read this entire thread, but I expected someone might ask me "Why don't I need a driver to use AirPrint?
Since there is no public AirPrint specification we are forced to speculate on how it could be done using Mac OS X whose driver architecture is public.
My original post describes a print driver as a translator. How do you eliminate the driver? The obvious answer would be to get the device with printable content and the printer to speak the same language. This might be done a couple of ways.
- Actually have the printer firmware able to interpret the format generated by the printing software. In Mac OS X the printing format is PDF and it is not uncommon for PostScript printers to also be able to print PDF files directly.
- The system software could be capable of generating output the printer can use directly. That case also exists in Mac OS X today. If you have a PostScript printer, from HP or anyone else, you technically don't need a "driver" because Apple provides one with the OS. This is very similar to #1 where the OS generates a PDF file from the graphics commands used to draw a page.
01-31-2011 08:35 PM
Your post above is very informative and I was hoping you could help me with some information. I have to write an explanatory paper about inkjet printer cartridges, and how they work for a science writing class. I've got a solid start on thermal bubble and piezoelectric (which I know HP doesn't use) technology, but I am confused about how printer drivers tell inkjet printers which nozzles on the cartridge to spray ink from--if there are so many nozzles, how does the printer know which one to use? Also, how does it know how and where to shift the nozzles to produce appropriate colors and shapes? I also read that piezoelectric ( technology converts mechanical energy to electrical energy--what does this mean for ink cartridges, if you know anything in this area? I suspect all this has something to do with the color and the desired size of the dot, but I haven't been able to find it anywhere. If you have time to explain this briefly, I would greatly appreciate it.
I know this isn't technically the place for this sort of question but considering the nature of your above post, I hope you don't mind my asking. If you can't answer, I understand--perhaps you could point me towards a book or site that does explain this technology?
02-01-2011 12:41 PM
I am not sure I can give you the details you seek, and not because I can't talk about it but because i do not know the answers. But I will tell you what I know from the software side of things.
No printer driver talks directly to the print heads. Drivers send print commands at a much higher level than that. If you have a PostScript or direct PDF printer the commands might look like "draw a line from here to here" or "render this image at this size and location" or even "draw this text at this location using this font". Of course I have not even tried to convey the syntax, only the general idea. The printer takes these commands and generates a page image. That image is then processed by the print engine to create a hard copy.
The simplest PDLs just receive the page image directly from the driver, usually compressed in some way. All the drawing is done on the computer before and the final image is sent to the printer.
As an aside, you can observe the way modern printers work to see this is so. If you ever used an old pen plotter the commands to draw text would actually drag the pen around the page to draw the text. But with a modern ink or laser printer each row of dots is drawn one at a time, and to have that happen the document being printed is transformed into a format that makes those rows easy to find and use.
The printer has hardware similar in concept but much less powerful than your computer. It's job is to turn the page images into hard copy and it does this by reading the image files and giving commands to the printer hardware based on what is in the image. The images are generated with a color plane for each color supported by the printer, and each of those planes must be processed separately to send commands to portion of the printer that prints that color.
That is a brief look at the software and a very high level overview of the hardware. One key part of the process is known as "halftoning". I will describe this briefly, but you may want to research it further.
Let's start with a "picture element" or "pixel". An image stored on a computer is saved as rows and columns of dots and each dot is known as a pixel. The dots on your computer screen are much larger than the dots printers put on a printed page. Each dot on your computer screen can have thousands or millions of colors because the display has fine control how much of each primary color is applied to that pixel.
Printers have much smaller pixels than displays, but also have a far smaller range of colors that can be used for each pixel. Looking at it simplistically, suppose that for each pixel you can choose to put a specific color there or not. That makes for some pretty limited color choices. So as part of the process a printer will treat a group of pixels (called a cell) as a single pixel and vary the number of dots that are on and off in the cell to change the intensity of the color perceived for that cell. The process of choosing which pixels are on or off in a cell is halftoning. Algorithms for doing this in a basic way are generally available, but companies protect their algorithms because some are better than others and everyone thinks or wishes theirs are the best.
Being able to vary the size of the dots effects the situation a little because it gives to the ability to change the shade of a single pixel, but halftones are still used because the number of shades that can be produced by changing the dot size is still fairly limited.
Sorry I am not much help with the ink technologies, I am more involved with laser printers.
A laser printer might actually be easier to describe: The image is drawn on the drum using a laser. The places hit by the laser gain an electrical charge which toner particles are attracted to. The toner is then transferred to a piece of paper using another differential in electrical charge and then the toner is finally fused (melted) to the paper.
Maybe that is too simple. Anyway, I hope some of this is of value to you. Good luck with your paper!