PDA

View Full Version : Color Consistency - Color Calibration



Rottweiler
07-26-2009, 04:39 AM
Hi Fellows,

Do anyone face the issue of color inconsistency after calibration?
:p

k_graham
07-26-2009, 07:57 PM
Let me count the ways

Ikon cpp500 delivered without patches which are necessary for the new gloss toner - without which its a 8050.)) but because its needing a curve for the gloss toner it is actually worse. Patches applied to reverse that but not told that new print driver is also required. Lets face it that should never have been a patch it should have been an install disk. I think this may also have been a Konica Minolta issue. So no matter what - all patches in place, along with printer driver to match.

Doc 240 that looses ability to calibrate on other than paper (have you tried for card, gloss etc) within a week of install, several installs - can't say for sure but replacement disks seem to have fixed. MD5 checksum as part of every installation would prevent flawed disks from release.

Techs (never Xerox yet) leave copier in off state. Garbage in garbage out - lets just say a butterfly test sheet is useful to ... butterflys. Pre-test copier with a wedding photo after every service call. Look for skin tone and on the white wedding dress shadows in Gray not yellow, pink or blue.

I think calibration to copier and also to Fiery should be done with the older 90 brightness papers as any UV whiteners skew the calibration that usually is papers in the 96 or brighter.

Does the unit have a toner refresh button - use it every time calibrating.

Limited humidity under 25% - add humidifiers - also best to copy most important side 1st before paper dries out and keep paper wrapped. Too much humidity - over 55% (I wish) - Air condition.
Dust in air - make sure to have air filtration
Dusty dirty filters in copier - replace with supplier that replaces these parts, they likely are delaying other parts as well, heck they are probably re-stringing Coronas by hand - not feasible, factory probably sets to calibrated tension, filters missing from copier, change suppliers.

What is perfect calibration - its not butterflies, its people and should closely match a hardware calibrated monitor.

Exceptions
Light people - prefer a tanned look
Naturally tanned - prefer a lighter look
Party goers - less red

You want a perfect match followed by the above tweaking

People pay the bills - not butterflies - we've banned butterfly test sheet approvals.

Rottweiler
07-27-2009, 03:52 AM
Thanks Pal.

Yup, my system do have its own set of toner refresh mode with some auto-gamma etc.

However Fiery had advised us to do the calibration that is available on the Fiery System.

But each time we do the calibration from Fiery system, we get a set of new color curve. This causes my system to produce a new set of color especially on mid-tone and highlight area.

Any recommendation from here?
:)

Paul_M
07-31-2009, 12:10 PM
First, and this should be obvious: color consistency from your printing system requires consistency in your setup and procedures.

As Ken suggested above, first try to stabilize the environment. Humidity and temperature are very important factors. Minimal fluctuations are more critical than optimal temperature and humidity targets; keep variations as low as possible. Keep your paper stored in a consistent manner. When a job is color critical, do NOT mix paper reams opened last week with freshly opened reams.

Most laser printers need warm-up before reaching a stable state. When it is realistically possible, print a few non color critical documents before calibration, instead of calibrating first thing in the morning

All laser printers nowadays include automatic image quality adjustment, a form of internal calibration. Some models let you force auto-adjustment from the control panel. If your model does not, powering the printer down then up will force this adjustment, as all printers do a reset at startup.. If your setup includes calibration controls specific to your printer, use them first, and only then perform the Fiery calibration.

If color is critical, you should not load/unload/reload different brands of papers of the same type (coating and weight) without re-calibrating your system with the latest loaded paper.

Most of the above advice will help you reach more consistent output, even in photocopy mode, for applicable engines; this represents the physical environment that your Fiery and printer are used in.

Now, more specific to your rip: the Fiery needs to regularly see prints produced by your printer. The Fiery “eyes” are the measurements produced by the instrument that you use for calibration. When you measure a calibration page, you are informing your Fiery about the current paper + environment + printer service state. Based on these measurements, the Fiery will calculate curves it will apply from now on, as a corrective action in order to meet a constant target.

If any of the above variables change significantly, color will vary, and the Fiery just continue to apply its last set of corrections, not knowing that your system’s base color has changed.

If you calibrate the Fiery and, 10 pages later, your printer decides to do an auto-adjustment (of itself, by itself) color will no longer be under control, as the Fiery expect. When a printer enters auto-adjustment, it attempts to reach consistent color density, using its own set of internal corrections. To avoid this problem, here is what you need to do: calibrate your Fiery after the printer’s auto-adjust. In this scenario, both the Fiery and the printer will be synchronized on a “stable” reference state.

Calibrate before jobs requiring quality control, especially if these jobs will be re-printed in the future. Calibrate after every service call. Calibrate every time your printer setup changes enough to change the underlying color response. Calibration is the way you can communicate to the Fiery that color has changed, and that it is time for it to apply a different set of corrections.

These steps will help for color “consistency”, i.e. same color, time after time.
Color “accuracy”, i.e. color matching a reference standard, requires and additional step: color ICC profiles representing the color produced by the calibrated state of this reference standard.

k_graham
08-01-2009, 10:45 AM
Xerox support has told me if consistency is a problem to reset 1st to go back to factory standard, try that, then do calibration as they said many calibrations, back to back can create the very problem.

My problem apparently was a factory faulty software issue as replacement disks allow different profiles for paper and card but you can rule that out by making sure you can do a paper and card profile. Alternative -if your supplier has a correctly working unit is to have them make a CLONE of drive which will get all patches exactly as correctly working unit. www.clonezilla.org




These steps will help for color “consistency”, i.e. same color, time after time.
Color “accuracy”, i.e. color matching a reference standard, requires and additional step: color ICC profiles representing the color produced by the calibrated state of this reference standard.


Color Matching a reference standard - Important -
I use
EFI RGB - Rel Colorimetric, Media Defined Profile.
(Fiery RGB2 - too saturated)
[alternative I'd use is NONE which is supposed to take from your application and is even less saturated than EFI RGB, but is not available on Doc12 Fiery, so I use a standard that is cross platform available on both]


CMYK Simulation Profile, SWOP Coated Full source - Use Media Defined
(Allows copier to correctly output from multiple trays)
(Alternative Output Profile Fiery dc250 100GCR 2F to
recognize more 100% black pages but my current understanding is that requires Full Output profile,
EFI correct me if I am wrong)

Spot Color Matching on (in theory to match a C,M,Y,K press it should be off as you can't tweek individual colors on press)
Pure Black Text Graphics on

This does not make the 2 copiers identical - it makes them as close to SWOP color as they and my Heidelberg DI are able to obtain.(if Europe instead of SWOP simulation I expect I would use ISO) But none of this is possible if the copier changes every time a service man is in. Think about it, if the copier doesn't change there should be no need for a Fiery calibration. Therefore a reference copy made off the glass should always look the same, check with a photo containing Human Skin and neutral shadows from White clothes. Save and date said perfect copy, if you can not obtain perfect copy make one on suppliers demo machine - use this as reference they must match - when you next make a copy and its not the same do Copier Calibration, if still not equal CALL SERVICE, they must make it match - this could require new drums, Coronas (no manual restringing) transfer belt, Developer. - If they are not leaving filters clean or are removing and not replacing - change suppliers. After Copier Calibration do Fiery Calibration - if calibration sheets are not outputting perfectly do additional - static discharge marks, toner splotches on calibration sheets not acceptable.


____________

Copier copy should match original photo, Hardware calibrated monitor with newer copier scanner should match original. Older Fierys with no built in scanner calibration required 3rd party calibration software. New units have a method of calibrating scanner, you will be asked during Fiery Calibration off the glass if you want to 1st calibrate scanner.

I haven't had any problem with new units but did encounter older units where 3rd party calibration software would no longer provide a matching scan - in both cases (a Canon CLC2400 and a Docucolor 12 ) this was resolved by replacing the scanner bulb.

Hardware monitor calibration - normally not possible by time monitor is 3 years old - send monitor to accounting they will appreciate large monitor, this shows importance of buying a hardware calibration device make sure it allows site use.

Lighting - Graphic standard 5000 Kelvin, my understanding is northern daylight is 6000-7500 kelvin, I use Sylvania 32 watt 6500 Kelvin Octron bulbs with electronic ballasts for flicker free performance. Maybe not the current graphic standard but should match what people see if outside.

Ken

Dennisg
01-15-2010, 08:35 PM
the software you are installingfor this hardware ACPI uniprocessor PC has not not passed the window logo testing to verify its compatibility windows XP continuing your installation of this software may impair or destabilize the correct operation of your system ether immediately or in the future. Microsoft strongly recommends that you stop this installation now and contact the hardware vendor for software that has passed the windows logo testing thats what it tells me i started to do system restore when my P.C started crashing like a week ago and this is the 2nd time i do system restore today cause my P.C crashes .. can any one help me out what do i have to do or download anything ? i have norton 05' scanned my system for virus and notting pops up i really need help can some one help me out please ???????????? unlock iphone 3g (http://www.youtube.com/watch?v=pqtVpplUYLQ)