Re: Epson 4900 Calibration
Re: Epson 4900 Calibration
- Subject: Re: Epson 4900 Calibration
- From: Kamil Tresnak <email@hidden>
- Date: Wed, 06 Apr 2011 23:40:29 +0200
Hi all,
Mike, slow down, i am sure, that Terry know all you wrote about colorimetric linearization - many of us here know all this.
I am long term user of EFI and GMG, i work with *EFI* many years ago when this was Best RIP, and was using GMG (and ORIS and others) for many many years.
I like EFI, i like GMG, both have some advantages, some disadvantages.
Both marketing departments use vendor speak. Sorry, but this is exactly what you are doing in end of your mail. Please, do not train us with sentences about "practical needs", "wizards" and so on. We are pros (and some of us are really old dogs).
So, from my real experience.
Small targets in EFI simply do not great job. It is not surprising for me, that you are using this careful words: "works fairly well" ... " almost as good" ...
In fact, difference in results between full IT8.7/4 and 46 patch is *very noticeable* ... no, this is not "almost as good".
This is not a game, we need a real precision, no "good enough" results.
And Mike, one note about previous mail.
You wrote:
"And for customers, the baselin is something they'll probably never encounter, as they will usually be provided with complete print environments for their printer and media".
YES .. this is why customers can not use papers from different vendors, unless they have full version of EFI XF with Color Manager Option. This is not feature, this is marketing based user limitation.
Last note. There are soooo much "vendor speak" today .. :( ... not only from efi ....
... "no, this is not only GCR"
... "yes, we have especially tuned inks for Epson printer"
..."no, this is not just OEM EFI RIP with different splash screen"
... "yes, our measuring device has tuned firmware"
Maybe in this little group we do not need this kind of discussion.
The only result is, that we, time from time, lost some great people from list.
(Yes, Marco on my mind).
Best regards
Kamil Tresnak
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* Subject: Re: Colorsync-users Digest, Vol 8, Issue 70
* From: Mike Strickler <email@hidden>
* Date: Wed, 06 Apr 2011 13:08:12 -0700
No, Terry, reprofiling is not needed. But let's back up a bit. First, yes, the linearization is colorimetirc, which means it's not densitomtetric, which is what the original question was about. So that's settled. Next, printer linearization is always by definition all about the primary colors alone. It has no other common-sense meaning. Relinearization should, if designed right, also include some means of adjusting the ink density of primaries, including the 100%, as printers tend to drift in this way, not in the way they overprint, for example. I'll expand on XF's options farther on.
Back to the baselin procedure. I was asked about the entire process, which sets ink limits (individual, total) and light-dark ink levels, as well as linearizes the primary ramps. A QC target, with overprints, is printed and measured at the end as a check that the net result of the ink limits (primarily) does not produce any anomalies. Notice I said "measured" and not merely looked at--so it is not merely a "reference," as you surmised. I assume (but can't confirm at this point) that some tweaking of the individual, 2- and 3-C, and total ink limits then takes place. It is sensible and should not be so controversial.
Now for recalibration. The whole idea of a relin is to adjust for a change in printer output, and that change takes place in the individual color channels. With XF this also includes a small profiling-like chart, 180 patches, like GMG's chart but smaller. It has a lot of 2- and 3-C overprints, including some with black (which is sensible considering that many inkjet blacks aren't "black" at all). This relin process is available on an automatic/scheduled basis with the Epsons that have a Spectroproofer. This process also contains an iterative phase.
The relin works fairly well, but there is more available. In most cases I prefer to reoptimize the profile. Here one can choose between a small chart or larger ones, including up to a full IT8.7/4. This is iterative, as with GMG, and can bring dEs down to very low levels. I do like the tiny 46-patch "Offset profiling Chart," which does almost as good a job as a full IT8.7/4, but with which is it possible to do 3 or 4 iterations very quickly. ( It is worth considering how much accuracy to expect (and how big a chart to use) when an inline spectro is used, but that is another topic.) It must be initiated manually but can proceed without any intervention and can be started at the end of a shift. Please note: In no cases do we make a new profile.
Not to be too hard on you, I think it's worth saying that one should have some experience with a product before making too many statements about how they work. It's important that readers are not misinformed. In reality, there are several proofing RIPs that operate at a high level of elegance and sophistication, not just one, and often the technical differences we dwell on are less important than the overall design philosophy and how well they fit with the practical needs of users. EFI XF does most of its geeky stuff "under the hood" and presents a wizard-driven interface with judiciously chosen opportunities for manual override. Like any RIP, it takes some training and getting used to, but it is highly adaptive and extremely friendly and productive in everyday use. That's not an easy goal to achieve, and it takes a lot of technology to get there.
Mike
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