Archive for July, 2005

Golden Nugget #7…Ink Jet Proofing Dry Time Prior to Measurement

Published
by
Jim Raffel
on July 27, 2005
in inkjet, measurement and proofing
. 0 Comments

*** User’s Group Conference News ***

Even though the date to receive our guaranteed pricing on rooms at the Mirage has passed it is not too late to attend the 2005 user’s group conference. If you are still interested in attending, we may be able to assist attendees in getting our hotel rates ($129/night for Sun, Mon, Tue, and only $199 for Sat. night!) Complete conference information can be found at (http://www.colormetrix.com/cmug05/). Before calling the hotel for a room, please give us a call to see if we can assist you with a room at the guaranteed conference rates.

*** Jim Raffel’s Week 7 Golden Nugget…How long do I have to let my ink jet proof dry before I measure it? ***

While there is not single correct answer to the question above, we have some basic guidelines from the field. Obviously, before following our suggestions it is very important to check with the manufacturer of the paper and ink that you are utilizing to print your proofs. They should know how long a dwell time is necessary before the proof is sufficiently dry that no more color shifting is occurring.

So, our general rule of thumb when we go in the field and assist our customers in setting a baseline or gold standard is to wait 30 minutes after the proof has finished printing before measuring it. We vary this a bit depending on the ink technology, pigment vs dye, but it seems to be a pretty good rule of thumb.

Now, we recognize that waiting 30 minutes to measure every proof may not be practical, but we are talking about the baseline or gold standard proofs right now. Once you have that down, it’s time to make another proof, to test for the optimum dry time for measurement of production proofs. Starting five minutes after the proof has finished printing measure the control strip every 5 minutes for half an hour.

Using the software you utilized to measure the proof take a look at the trend line analysis of the Delta E shift over the 30 minutes. You should be able to see a clear place where the shift levels off. Again, depending upon your environment (temperature and humidity), and proof type (pigment vs. dye) this could be at 10 minutes or 20 minutes.

That’s it! You now know how long to wait in order to get accurate proof verification measurements. If by any chance you are having trouble getting the trend line analysis I mentioned above out of your software….I know a great little software company called ColorMetrix that will be able to assist you in fixing that problem!

Golden Nugget #6…Why Measure?

Published
by
Jim Raffel
on July 19, 2005
in measurement
. 0 Comments

*** Introduction ***

In the last several weeks several readers have mentioned that they are forwarding these e-mails to others. That is perfectly fine, but anyone can get on the list by sending me their complete contact information.

*** Jim Raffel’s Week 6 Golden Nugget…Why Measure ***

Over the years I have gotten the comment that ColorMetrix does not “fix” the problem. This comment would be similar to a carpenter saying that a tape measure does not fix his problem cutting 2X4’s to a specific length when he had been eyeballing it all along. If the tape measure is not used, or is used incorrectly, the statement is accurate.

If on the other hand the tape measure is used to measure and mark each 2X4 BEFORE it is cut many fewer 2X4’s will end up in the waste pile (Remember when your Dad taught you to measure twice cut once?). The same holds true for the measurement of printing process.

Here is just a partial list of all the places we should me measuring to improve color reproduction:

  • Any monitor used for critical color work (yes monitor calibration is a form of measurement).
  • Any proof viewed for color (I know a great little software company called ColorMetrix that can help you with this!).
  • Printing plates need to me monitored with an accurate plate reading device, so we know what dot percentages we are sending to press (You can also catch processor problems by doing this, just ask Gary Briney who will be at the User’s Group Conference again this year).
  • Press sheets – for Density, Dot Gain (TVI), Print Contrast, Trap, and Colormetric values like L*a*b* with Delta E tolerances.

If you are not measuring in all these areas, please ask yourself why not? It is neither difficult nor expensive to acquire the tools and knowledge necessary. Even better, once you have made the investment, you will be amazed at how quickly the returns begin to flow in via reduced time and material waste.

Imagine using the data you collect in the pressroom to tweak the curves in your CTP device. If press performance changes you can adjust the device to compensate for the changes, and have a more stable production environment. Then, you can utilize your plate reader to confirm that the changes made in software are making it to the actual printing plate.

Imagine verifying that each proof made is color accurate and can be reproduced on press. This also means that the proofs you show your customer can be matched on press. I am not sure I can imagine a worse scenario than putting a proof in the hands of the customer that “they love” that we are not capable of matching on press.

So, if you are not measuring in all of the above mentioned places, perhaps you should considering investing in the correct tool for the job and getting it done today.

Golden Nugget #5…Density & TVI or L*a*b?

Published
by
Jim Raffel
on July 13, 2005
in L*a*b*, TVI (Dot Gain) and density
. 0 Comments

*** Introduction ***

Next, I want to let you all know that since the inception of the golden nuggets idea both of the Mikes at ColorMetrix (Michael Litscher-CTO & Co-founder; Michael Woods-Technical Services Manager) have been after me to blog the golden nuggets as well as sending them out as an e-mail. While I thought it was a great idea from the start, I just did not have the time until this week. So, from this point forward after I send the golden nugget e-mail I will also post in it on the http://www.jimraffel.com blog. The blog has two other significant advantages; readers can post comments to each message; and I can post follow-up information or addition topics between e-mails.

Well, once again our customers and my associates in the field have made writing this week’s e-mail both easier and more difficult all at the same time. I was provided with many great ideas this week, but can only write about one. I also believe one of the ideas is significantly technical that I will need to write a white paper in the future and publish that on the blog site. The topic I will not be covering is closely related to the evaluation of inkjet proofs and press sheets with Density/TVI vs. L*a*b*. Eric Magnusson (www.leftdakota.com), explained to me this week how he uses the L* value of CMYK on inkjet proofs to derive approximate Dot Area values. While I find the idea interesting, I need more time to test it, and run the math by Michael Litscher our CTO.

*** Jim Raffel’s Week 5 Golden Nugget ***

I settled on the topic of using Density & TVI vs. L*a*b* to evaluate the difference between inkjet proofs and press sheets not only because it came up several times this week, but it keeps coming up every week in on-site visits and telephone support calls. This topic stems from the reality that densitometers use very specific filters defined by international standards to measure the CMYK ink set. These filters are tuned to the spectral response of the process color ink set. The inks used in ink jet printers do not have the same spectral response as the CMYK inks used on printing presses in our industry.

So, while the solid color bar patches of CMYK on the proof and press sheet look visually the same to our human eye (capable of seeing the entire visual spectrum at all times), they can and often do look considerably different to a device which simply has three filters (utilized to filter the visual spectrum into thirds). This also means that any value derived from a potentially flawed density value (i.e. – Dot Area, Dot Gain-TVI if you prefer, Print contrast, Trap, etc…) are equally unreliable as evaluation tools concerning the match of an ink jet proof and a press sheet.

Michael Woods and I have seen time and time again in the field inkjet proofs that do not visually match, but have density and TVI values within tolerance (we have seen the reverse also). As recently as last year I know of at least one inkjet proofing manufacturer who still utilized density trends to verify proof consistency over time. One of our mutual customers complained to me that while the manufacturer’s software and ColorMetrix both reported the proofs being in specification, the visual variation was not acceptable. I asked them to view the trending data in Delta E, and was not surprised to hear them say that shifts or 6-8 Delta E (CIE L*a*b*) in the balanced 3 color grays appeared to be the norm not the exception.

So, is there any value in measuring the density of inkjet proofs? I am not convinced there is. On the other hand, since it is easy to collect and store the data, why not do so. Also, one of my customers pointed out to me this week that they monitor Magenta density of their inkjet proofing system to catch changed changes in ambient conditions like humidity and temperature. While I have not seen this first hand, I am told by the customer that they can get shifts of .07 in Magenta, and still have Delta E variation of less than 3.5 (acceptable level for this instillation). But the movement in the Magenta density warns them they are having humidity problems that could cause the production of bad proofs soon.

The above example is what process control is all about. If you do not measure it, you can not control it. Then, when problems do occur you can go back and look for shifts in the measurements. After identifying a key metric, as our customer above did, you can add that to your daily monitoring, and improve quality and productivity while at the same time reducing waste.

Golden Nugget #4…Proper Color Viewing Conditions

Published
by
Jim Raffel
on July 9, 2005
in viewing conditions
. 0 Comments

Once again this week our topic has been set by a golden nuggets reader. I will get to that in a moment, but first I wanted to share some observations I made this 4th of July weekend. I had the honor and pleasure of joining my son’s Boy Scout troop for their last day and half of summer camp. Now, you may be asking yourself what this could have to do with the printing industry. Well, it showed me that print is not dead or dying as many a naysayer has been predicting for a long time.

It also showed me once again why I got into this great industry. At Boy Scout camp (at least at our Boy Scout camp) no electronics are allowed. What is allowed are books, Magic cards (a game based on decks of trading cards that some one had to print!), Scout Books, merit badge books, a Wall Street Journal (yes, that was mine not the boys) etc…. I think you get the idea, lots of printed materials. I watched a group of 20 boys (sorry, young men really), keep themselves busy for 4 hours with several decks of Magic cards, and a tournament they set-up and scored on a piece of paper. For those of you with children; that’s right no Xbox, Game cube, TV, or other electronic gadgets, just good old fashioned print.

I also was reminded of the purpose of that first printing press…the archiving and sharing of human knowledge for the ages and most importantly the masses. When I had a little downtime, I was flipping through my son’s Boy Scout book. I was quite honestly amazed at the wealth of knowledge contained in that relatively small book. All I can say is that if I ever get lost in the wilderness that is the one book I would want with me. All of us just need to keep searching for the niche’s we can serve better and longer than any other media.

*** Jim Raffel’s Week 4 Golden Nugget ***

I have a friend (let’s call him Doug) who is a technical sales representative for one of the few remaining national distributors left in our industry. Doug works out on the West coast, and specializes in the Flexographic part of our industry. Doug has also been using ColorMetrix for several years now to successfully fingerprint dozens of flexo presses up and down the west coast as the plates are converted from analog to digital (CTP).

Well, Doug called me last week with a question I thought would benefit all of us. He was in the final stages of a CTP conversion. The re-curved plates were on press and he had achieved the correct densities and dot gains that his many years of experience told him should be resulting in a nearly perfect print. Doug, however, was looking at a balanced quarter tone grey (25/18/18) and it was looking a little red press side. Doug told me that when he took the sheet outside in the natural southern California sunshine (this probably will not work in the mid-west at 5pm in the month of December), the grey looked prefect.

My first question to Doug…what kind of light booth does the customer have press side. Doug’s answer…”a home made one.” Wrong answer! The light booth had no sides to keep out ambient press room light, and Doug could not confirm that the bulbs even met the 5000K standard. The human eye is perhaps the best judge of color in the world, but only in proper viewing conditions. I reminded Doug that his employer sells at least two brands of light booths that I know of (http://www.gretagmacbeth.com and http://www.gtilite.com) and suggested it was time his customer purchase a proper press side light booth.

I am of course quite certain everyone else reading this has a proper light booth press side. If by some chance you do not…it really is time to call your dealer sales person, and at least have them provide you the information you need to make an informed decision about why you will run jobs worth tens of thousands of dollars on a press worth millions, but you won’t spend 5 grand (or less) for a decent light booth.

*** 2005 ColorMetrix User’s Goup Conference Info ***

Remember, we will be picking a selection of these topics to discuss at the 5th annual ColorMetrix user’s group conference in Las Vegas August 21-23 at the Mirage resort and casino. More information is available at (http://www.colormetrix.com/cmug05). We also have a session planned in which we will discuss the difference between the many light sources (illuminants) available in the graphic arts industry.\

Well, that’s it for week 4. Please feel free to e-mail back (raffelj@colormetrix.com ) and let me know what you think. If you have ideas for golden nuggets, that would be great too.

Golden Nugget #3 / Urgent ColorMetrix User’s Group Info

Published
by
Jim Raffel
on July 9, 2005
in measurement
. 0 Comments

Because of the upcoming ColorMetrix User’s Group Conference, we needed to change the e-mail around a bit this week. In order to not send multiple e-mails to many of you on this list, I will first address urgent issues regarding the User’s Group Conference August 21-23 at the Mirage Resort & Casino in Las Vegas, Nevada. If for some reason you are unable to join us, feel free to skip this section.

User’s Group Conference Issues

Issue #1: FREE ColorMetrix golf shirt offer final extension ends June 30th. If you register on-line (http://colormetrix.com/cmug05/) by midnight June 30th, you will receive a free ColorMetrix golf shirt when you arrive at the conference. I have been assured by our supplier that this is the last extension if the shirts are to be ready on time. So if you are coming there is no longer any reason to procrastinate. Why not register now before you read the rest of this e-mail!

Issue #2: Hotel Rooms. If you are registered or will be registering please remember to call the Mirage at 800-374-9000 and make your hotel reservation. We have a limited number or rooms blocked and our special rate expires July 15th. (This applies to our sponsors also)

Issue #3: ColorMetrix Success Stories. If you are a user and will be coming to the conference, please let us know if you would like to share your ColorMetrix or GcX success stories with other users during one of our panel discussions.

Now back to the normally scheduled golden nugget e-mail

At the close of the Week 2 golden nugget I mentioned that our intention was to write about the influence of ambient UV light on measurements. For two reasons I am putting that subject on hold for a week or maybe more. First, I did not have time to run some simple tests in our office to perform to confirm results I have seen in my travels. Second, and by far of more importance, I received two replies to the week 2 golden nugget that I feel need to be shared with our readers.

Let me start by sharing the quote that motivated me to start writing this e-mail each week. “Salespeople [insert your profession here] are the smartest people in the world. As I go from audience to audience they all have one theme among them: everyone knows everything. Problem is they are not doing it……As you read through this book [e-mail] don’t tell yourself, “I know that.” Rather ask yourself, “How good am I at that?”” – Jeffery Gitomer “The Little Red Book of Selling”

So, last week a reply cam from a reader/customer that not only knows this stuff really well, but also is among the best in our industry at doing this color measurement stuff. He suggested I might be doing a disservice to our customers and readers by providing this less than perfect technical information. I took his point to heart and need to provide additional information about measuring on white tiles purchased at a home improvement store. First, the customer doing this has a closed loop situation (i.e. – they are doing their own pre-press for their flexographic presses). This makes for a bit of a unique situation because they do not share information with outside sources. In contrast, our reader who raised this concern has a great point when you are printing national magazines and ad proofs are coming in from many places. You need to know they have been measured under consistent, known, and repeatable conditions.

This led me to refresh my knowledge of the standard measurement conditions already suggested by organizations like ISO and CGATS. Well, Google is a wonderful tool…..try typing the following into a Google search box “ISO standards for spectral measurements in graphic arts” On the first page alone you will find two downloadable PDFs (one by David Q. McDowell and another from color.org) that go into the kind of depth we do not have the space for in a weekly e-mail. Please get them, read them, and send me some comments on what kind of surfaces you measure on.

Jim Raffel’s Week 3 Golden Nugget

Our second reader/customer’s feedback/reply provided such a great idea we decided we had to share it now before it got lost in the stack of stuff in our office (I know you all have very neat organized desks and don’t lose important things, but I do). If you are running a press fingerprint, which could include an ECI or other color management target, how do you simulate printing on the reverse side of the sheet without influencing the readings with pictures on the reverse side? Here’s a partial quote from one of our customer/reader’s:

“Another consideration for measurement … oh yes, it comes off a press!

For that reason show through is an important factor, for that reason “snap off” is important in creating the acceptable image. No ink (blank second side) is not an option, the inked side will follow the blanket around and cause slur in the unit. So to produce press samples that represent real world printing, without influencing the readings with pictures on the reverse side, …[deleted secret sauce reference]… grey enough to simulate show through (if paper is not opaque) and enough ink in the press to prevent “snap off” from causing dot distortion (color distortion too).” - Anonymous

Since this individual asked to remain anonymous I have deleted his exact secret sauce but left enough information in for you to figure out what needs to go on the reverse side of the sheet.

Well, that’s it for week 2. Please feel free to e-mail back ( raffelj@colormetrix.com ) and let me know what you think. If you have ideas for golden nuggets, that would be great too.

Golden Nugget #2…Consistent Measurement Environment

Published
by
Jim Raffel
on July 9, 2005
in measurement
. 0 Comments

If you are joining us for the first time, here is what the golden nuggets are all about. At ColorMetrix we spend a great deal of our business life on the road. We have come to realize that we take one golden nugget away from almost every stop we make on the road.

So, the purpose of this weekly e-mail will be sharing the best golden nuggets from our travels with all of you. The focus of the golden nuggets will be color measurement (this is after all what we do at ColorMetrix). It will by and large not be focused on our software, but instead on best practices we observe; tips and tricks; and even stuff that should not work but does!

*** Jim Raffel’s Week 2 Golden Nugget ***

At the end of the week 1 golden nugget I asked the question what environment should samples be measured in. There is no easy answer to this question except for an incomplete one; a consistent environment! The standards organizations have made statements about measuring on a white surface; a black surface, on top of a stack of x number of blank sheets of your substrate, etc… Let me say this is all good information, and should be tracked down in order to make your consistent measurement environment as technically correct as is practical. There are, however, writers better suited than I to cover the exact standards and how to apply them (any guest nugget writers out there?).

What we want to share is a simple solution one of our customer’s has implemented. First, this customer settled on the concept of a uniform white backing for all measurements. Ah, but what uniform white backing? This customer has many locations around the globe that measurements are made at, so this complicates the solution a bit. While a single location operation can pick a single light booth, and always measure in that specific booth taking advantage of the white surface supplied by the light booth manufacturer, our large customer did not have this luxury.

So, here is what our customer did. They went to a local home improvement store and purchased a box of 12”x12” off white tiles. They then took those tiles back to their office, and measured them for consistency. Basically they created a large grid on one tile and measured each quadrant of the grid. The Delta E turned out to be quite tight (less than 2). They then took random measurements on the rest of the box, and found the Delta E variation remained acceptable to them (still less than 2 from the baseline). Finally, they went back to the home improvement store and purchased several more boxes of the same lot number of tiles. Keep in mind this solution worked for them, you may need to pick a different easily accessible surface.

I have heard through the grapevine that one of the leading manufactures of color related products will be releasing a disposable white or black verified option to serve as a measurement backing. If this actually comes to market it will be a great solution to a big problem in our industry. Let’s be honest how many of us have taken “quick and dirty” measurements on our wood grain desktops? (I raised my hand)

Next week I am going to continue this subject, and address the issue of ambient light when measuring samples which contain optical brighteners.

*** IMPORTANT 2005 ColorMetrix User’s Group FREE golf shirt update ***

As I mentioned last week, we will be picking some of the best golden nuggets between now and the ColorMetrix User’s Group Conference to incorporate in a technical discussion. If you find these nuggets interesting or informative you should consider joining us in Las Vegas August 21-23 (http://colormetrix.com/cmug05/). The deadline to register AND receive a free ColorMetrix golf shirt has been extended to this Friday June 24th. We need to get the shirts ordered, so the free shirt deadline will not be extended further. If you are thinking about coming now is the time to register!

Well, that’s it for week 2. Please feel free to e-mail back ( raffelj@colormetrix.com ), and let me know what you think. If you have ideas for golden nuggets, that’s would be great too.

Golden Nugget #1…UV vs Non-UV Measurement

Published
by
Jim Raffel
on July 9, 2005
in UV and measurement
. 0 Comments

I spend a great deal of my business life on the road. Some of that time I am visiting clients for sales, training or good will purposes. Much of the rest of the road time is spent at trade shows and conferences. What I have realized is I take one golden nugget away from almost every stop I make on the road.
So, the purpose of this weekly e-mail will be sharing the best golden nugget from the week with all of you. The focus of the golden nuggets will be color measurement (this is after all what we do at ColorMetrix). It will by and large not be focused on our software, but instead on best practices we observe; tips and tricks; and even stuff that should not work but does!

*** Drum Rolls Please….Jim Raffel’s Week 1 Golden Nugget

Since I spent 3 days at the IPA technical conference, it was difficult to pick a topic for this week. Before the conference I had already decided I wanted to discuss UV vs Non-UV filters in measurement instruments in an early golden nugget. So, the winning topic is…UV vs Non-UV filters.

Mike DiCosola (Chromaticity) gave an excellent presentation at the IPA technical conference on color measurement, which in many ways confirmed what our customer’s have been doing in the field for about two years. If your primary use of the instrument is process control, and the primary object you are controlling contains a large quantity of UV brighteners, you should be using an instrument with UV filters. Why you ask, well Mike gave a good refresher on what a UV filter does.

A UV filter blocks the UV portion of the spectrum (remember we can’t see UV light, so this act by itself does not change visual appearance). By blocking the UV light at the source, this light which excites the florescent material in optical brighteners, never reaches the object being measured. Excited florescent material glows (I,e, - gives off light), causing a situation where you could potentially return more light to the measuring instrument than it sent out.

The other problem with florescent material is that the glowing is not linear. In other words, a small amount of UV energy will cause the brighteners to glow “a little bit”; a large amount (repeated measurement of the same sample over a short period of time) will cause the sample to “glow a lot!” A threshold is eventually reached, and then the measurement becomes more consistent, until the object is placed in a dark place for a period of time.

OK, so my final note about this subject is that UV filters do nothing about ambient light in the room. Remember, the filter is filtering the light source of the instrument, not the light source in the room you are measuring in. So, what environment should you measure your objects in (printed sheets and proofs for most of us)? I think we will leave that for another golden nugget.

*** Shameless Plug

We will be picking some of the best golden nuggets between now and the ColorMetrix User’s Group Conference to incorporate in a technical discussion. If you find these nuggets interesting or informative you may want to join us in Las Vegas August 21-23 (http://colormetrix.com/cmug05/)

Well, that’s it for week 1. Please feel free to e-mail back ( raffelj@colormetrix.com ), and let me know what you think. If you have ideas for golden nuggets, that’s would be great too.

Welcome!

Published
by
Jim Raffel
on July 9, 2005
in blogging
. 0 Comments

Many people have encouraged me to blog the Golden Nugget posts. I will continue to send them via e-mail, but you will also be able to find the history here if you ever need it. As always let me know what you think. Thanks! - Jim