Questions about color conversion of single process colors with Fiery

[pworden]

I sent test files that were processed on a Fiery RIP. Noticed that a gradient of 50%-0% black switched to process around 25%. Also, a CMYK image in a PDF had a black-only screen changed to process. The tech printing the test mentioned that the Fiery converted everything to LAB first... I did notice a screen control strip retained the black-only area so I'm not sure what was going on with the test file. I realize this isn't very detailed information but wondered if anyone had a general description of how the Fiery handles color conversion of elements that are intended to print specifically in single, process colors. Thanks for any info.

[DigiCorn]

I can't tell you how a Fiery reproduces color because I'm not that technical, but I can tell you that typically on a digital press you're dealing with toner, which is opaque. On press or ink jet proofers, your ink is transparent. Right away you've got a battle similar to RGB and CMYK, where I like to describe RGB as being "light based" in which the absence of light results in black, and the presence of all light results in white, where CMYK is the opposite in that the presence of all colors is black versus the absence of all color being white (or paper color).

We took our icc profile from our proofer and applied it to our Fiery, and then tweaked it by eye. It will never match a press sheet, but we got it to what we consider and acceptable level.

[pworden]

Thanks. I understand the RGB / CMYK differences. Sometimes some of our customers - usually agencies - design areas that are intended to be a black screen and ONLY black. My test files showed some of those areas converted to process mixes. Weird that in the one area particularly, the 50 - 0 black-only screen gradient turned to process from about the 25% down to 0. Just wondering why and mainly, if that's something we could control or override when we want areas to be just as designed. For instance, on the Spire RIP, we can set the profile to "Direct" which takes the screen values as supplied without reconverting.

[DigiCorn]

Thanks. I understand the RGB / CMYK differences.

Yeah - that was a no brainer. I was just explaining how we sell it to the customers when we're trying to match a digital piece to a printed piece.

We really only use certain digital stock on our color digital press, and I have tried my best to calibrate uniquely for each sheet. Our Fiery is ancient, and only allows 10 different profiles, so I used them all. If a job runs on a stock not already profiled, then they are out of luck for color matching, and they are told before the order is placed.

You should have a densitometer connected to your Fiery and that densitometer should have come with a calibration strip. When was the last time to calibrated, and when was the last time to ran a relinearization? If you haven't already, you should do this to get it "back to factory standards." Then, if you desire, you can take some readings and adjust your curve accordingly.

[pworden]

I just sent test files. We don't currently use a Fiery but are looking at an additional digital press. Just trying to see how it performs and wondered about this issue that showed up on the test prints and if there was any way to get single-color results when I want it. I prefer answers from my peers to the ones from sales :-)

[Joe]

It could depend on a lot of different things. Are you printing to it or using hotfolders? What color profile is it using? What kind of file are you sending to it? Does it have native transparency? Fiery rips do not handle native transparency well. The only thing consistent about the Fiery is that it is inconsistent dealing with files,

[David]

I have found that a lot of these use a SWOP profile, which I have seen do weird things (like make 100% black type turn into 4 color, with a 90% black).
I would first look at the conversion, from what icc to what icc profile.

[pworden]

Okay - sounds like it might be possible to get the same screen values on output as on input with the right profiles? The test was a drag/drop to the RIP with Gracol 6 as input (honored) and the paper profile specifically as output. I had spots and transparencies, too, as part of this 11 x 17 2-sided test file. Good to know that might be an issue.

[Greg_Firestone]

My first question would be what are your color management settings in the RIP?

When you say the input was "Gracol 6", was the input tagged or untagged CMYK?

Greg

[pworden]

Images included GRACoL6 profile. Complete PDF was PDF/X4 with Output Intent "identifier" FOGRA27, "info" Coated GRACoL 2006 (ISO 12647-2:2004)

[pworden]

Looks like I should follow up with the Fiery analyst from this point since I really can't answer that question properly. It was the first time I saw the Fiery and I don't know the exact settings used on the test, just recall that they confirmed my PDF was set as GRACoL6 and they chose an output profile specific to the paper being used. I liked the paper catalog feature and the color control possibility in general, just was concerned about the LAB to final conversion and how that worked. I use an Epson 9600 here at work and with that, and its older software, can never get a true black-only print but a multicolor simulation instead. I would like to be certain that I could get single-process color output from the Fiery.

[Grimace]

We run a Fiery RIP on our Konica 6501.
As far as I know, unless you specify grayscale under the color settings, it always prints with all toners.
And having only K in your image file doesn't trigger the gray scale setting, you have to select it specifically.
It's all about the click charge.

That doesn't help if you have mixed gray and color on same sheet.

[gnubler]

Is the queue setup different if you have a Fiery? We have the 6501 with a Creo RIP and I set up separate grayscale & color queues.

Also, if I send a mixed file to a color queue and a page has only K it counts as a black click.

[Grimace]

Is the queue setup different if you have a Fiery? We have the 6501 with a Creo RIP and I set up separate grayscale & color queues.

Also, if I send a mixed file to a color queue and a page has only K it counts as a black click.

yeah, that sounds different. I can identify what pages I would like in color or just gray(k only) and it will print that way. But it will not do it automatically. Depending upon the document, I can also have text print as "Black only". But much of the stuff we get is a mixed bag and getting CMYK text with just black is apparent. To be fair, I haven't really been a power user. I'm sure there are things I could do different to get better results. But no one is asking for better!
Hell, most of the time the sausage next to me just sends every file as full color. Click charge? What's that?

[gnubler]

Hell, most of the time the sausage next to me just sends every file as full color. Click charge? What's that?

Only a Sausage would do that. I wonder if he equates unnecessary click charges with future paychecks?