KM 6501 - Fiery - colour has never been right ?

[Greg_Firestone]

Yes its fairly consistently wrong after calibration. Always too red.

I think as stated its what the profiles are doing which is the problem... If you just turn off the profiles it prints as a press should. Bearing in mind that of course the CMY colour of the toners doesn't match offset ink colour, which i guess is why they try to profile it to compensate, But the way the profiles are implemented is just wrong.

For instance, i guess they figured that for 100% cyan the konica produces naturally they needed to add some magenta to match offset ink, which is fair enough, but i have laid down 5% screens of cyan before and with the profiling on, you can visibly see magenta dots with the naked eye... Surely at such a low density there would be no need to add ANY magenta ?

That's good that you can get some type of consistency after calibrating. After reading the other comments, I agree that it seems the profile may be the culprit. Is it using KM provided profiles or are you using a standard profile (ie Gracol or Fogra). You can definitely try to fingerprint the press after a calibration. You could take it a step further and try to implement a device-link profile if your trying to target a certain spec.

Just out of curiosity, have you ever tried creating a test file with solids and tints and compared the output with both color management enabled and disabled? If you run disabled, your colors and tints should be pure with no contamination from the other inks. You could also see how much dot gain your getting.

Greg

[Correct Color]

Well, the profiles seem to interpret images differently to vector art.

When you through for instance a file with a solid black vector background that has an image which has been flattened (say there is a drop shadow that has been flattened to an image in the middle of the black), the rip prints the vector black as pure 100%, but prints the black that is part of the image as 4 colour black, so we get this noticable box.

Turn the profiling off and it prints exactly as it should.

That's a RIP issue. Not a profiles issue or a printer issue. Usually what causes this is that the RIP sees the area around the drop shadow and the area immediately around it as a raster image, so it applies its raster rendering intent to that area. The areas outside of it are still rendered as vector, and that causes the difference.

As far as the machine printing greys correctly with profiles off, it's pretty simple. With profiles off, the machine prints grey using almost completely black. Since the RIP is sending the information in the file through un-colormanaged, and in the file the area is most likely predominantly black.

However, color managed, that same area to the RIP becomes a Lab value that passes through an ICC profile with some sort of black generation built into it. Typically stock profiles on CLC machines start the black very late, as in after L 50. So what that means is in the print with profiles on, that same area that's nearly all black unprofiled now is most likely made up completely of CMY, with no black in it at all.

What calibration does is attempt to make all a machine's single channels print--if not linearly--at least predictably. Then an ICC profile, built on top of that calibration and expecting it, characterizes exactly how the machine prints. So of course the profile is expecting the machine to print in only one state. That's the only state for which that profile is completely valid. And if the calibration is off by even a small amount compared to what it was when the profile was made, you'll get exactly the issues you're describing.

So there really isn't to me too much doubt that all your issues are caused by nothing more than a bad profile, or even set of stock profiles, and can be remedied pretty easily.

As far as these machines not being capable of being tamed, as one poster said, I can't say I agree. They have their limitations, of course, and they do have stability issues...

But surprisingly, what I've found is that lots of people simply use those excuses as just that, excuses.

Properly profiled and with a proper workflow in place, these machines can be made to produce predictable results.


Mike Adams
Correct Color

[prakashshetty_thane]

Our new printer KM 6000 also has the same problem. I've noticed most printers have a tendency towards one or the other color. The other Xerox printers I've owned have had either a pinkish (magenta) hue or a yellow hue as is the case with our 700.

The current Konica has always been pink but will not print a good red color, everything looks orange especially when compared with output from our Xerox.

We've calibrated to no avail, and even went as far as creating profiles to feed the rip for different paper types we commonly use. Rather than get us truer color this only served to make the color even further off from what we see on our offset presses despite having created profiles for the presses themselves and having our copiers simulate the color from the press. In my experience there is no magic bullet with color on these type of devices as they seem to vary widely even with regular calibration.

We have a brown color we run quite often for a chocolate company on our digital equipment and have taken to calibrating just before running it each time. Despite this the color of browns NEVER match without tweaking...seems as though the calibration does next to nothing as far as preserving consistency.

What I find hilarious is that our technician seems to think that calibration will fix a whole host of problems. One time we had a "greenish" bar printing at the head of every sheet for about two inches then it disappeared further down the sheet. His first thought was to "calibrate" to get rid of it. It's stupidity like this line of thinking that is the real problem with many of these independent dealers who know next to nothing about color or calibration. I think you are victim to one of these dealers as are many of us.

Which RIP are u using?

If Its IC-306 maybe i have a solution for this Red color issue in KM c6000 m/c since i have faced the same problem in my m/c.

[ChrisD]

We have a KM6501 working for about 3 years, we found that when we run an offset sheet, SRA3 size, 350gsm, slightly over the specified weight we have the same problem. The other issue of colour may be due to the paper, I found that when we tried Xerox Impressions gloss most of the problems were resolved, but I must say that our KM engineer knows his stuff and seems able to adjust the colours for us. We bought the calibration kit, very expensive - to work with the Fiery rip but we don't bother any more, it seems better with no calibration.