CHROMiX ColorNews Issue #18 - Chromatic Adaptation
Welcome to ColorNews, a periodic update on things related to Color Management. We are striving for a regular consistent newsletter of high value to our customers. Please let us know what your interests are so we can address these concerns in our coming issues.
C H R O M i X C O L O R N E W S
Several Quick Notes of Interest:
** CHROMiX will be discontinuing the FREE Eye-One Display promotion after June 30th. See details below.
** Steve Upton and the CHROMiX tech gang have a new ColorThink software update coming very soon that will also have some very cool additional features. See details below.
** GretagMacbeth has a new version of ProfileMaker v5 available at an introductory special. See excerpt in Color, Product & Industry News below.
** Don Hutcheson has some revealing thoughts about Fuji discontinuing the Velvia 50 film in Tech Notes below. Also, be sure to check out Tech Notes #2 and #3 for two, very good on-line articles.
** CHROMiX has a special offer to all GIA 'Color Without Limits' seminar attendees. CHROMiX will give you $225 credit towards the purchase of an Eye-One solution. See Ad below.
** TRADE in that old device and get $80 to $200 off of your next Eye-One purchase! See details in Ad below.
** Chromatic Adaptation - an article written by CHROMiX President Steve Upton
Table of Contents
1. CHROMiX News
Since our last ColorNews Issue #17 here's what's going on at CHROMiX: (busy as usual)
Our new working relationship with eVolve, a great Seattle-based training group is, well, eVolving. There are two new events to tell you about:
Free CHROMiX / Evolve seminar "Adobe Creative Suite 2: Achieving Consistent Color in CS2". Come learn about the color management process and new color management capabilities in Adobe Creative Suite 2. Using the suite's "nerve center" the Bridge, you can now achieve consistent color in Photoshop, InDesign, Illustrator, GoLive and Acrobat. Join us at Adobe's Seattle campus June 15 at 5:30 for cocktails, hors d'oeuvres and 6:00-7:30 for the seminar. For registration and more information follow this link:
We will be offering a new co-developed class entitled 'PHOTOSHOP DIGITAL WORKFLOW with COLOR MANAGEMENT'. It is a 6-hour workshop on June 21st from 9:30 am - 4:40 pm for $300, and will be held at the Seattle Evolve facility. We would love to have you join us. For more details follow this link:
Steve Upton will be presenting a WebEx seminar for the IPA on "An Introduction to Color Management" on July 13, 2005. This is intended as an intro for designers and art directors. The registration page is not yet online. Watch the IPA and CHROMiX sites for more information.
ColorThink 2.2 beta is now available. In a free update to the current ColorThink software, we are fixing a number of bugs and folding in a few new features. One new feature is the ability to read Monaco Profiler Export and Session files and export them in the standard CGATS format that GretagMacbeth uses. So you can use ColorThink to convert Monaco Profiler readings for use with GretagMacbeth software. This also means you can use Profiler to drive the DTP-70 and then pass the readings through ColorThink and build profiles with GretagMacbeth. If you want to play with the beta, please go to our download page and take a look. (It will use your existing 2.x serial numbers.)
ColorNews is now available in the RSS newsfeed format. CHROMiX will be using the RSS feed capability to post updates and announcements to our website and any RSS newsfeed subscribers. What this means to you is that CHROMiX will devote a part of our website to a live news feed of Color Management and related industry news - so you'll only need to go to one place to get any and all relevant information. If you have upgraded your Mac to Tiger, RSS reading is available as part of the new Safari. Just go to our website at Click Here and click on the blue RSS icon on the right side of Safari's location bar. To directly link to the feed file go here:
The CHROMiX ColorForums are growing in popularity and usage. Thanks to everyone who contributes and participates. ColorForums.com is the first full-featured online forum dedicated to color management tools, techniques and support. Not only is there a clear web-based interface to all forum topic areas, but it is backed up with a comprehensive email system. You can read and post messages via the web or email, so those of you who don't always have time to surf the web can have the color management community come to you. If you have a technical question or would like to discuss a topic, give it a try!
Color, Product & Industry News
Apple just released Tiger, it's new Mac OS X operating system software. Mac OS X v10.4 (Tiger) has some very cool features: Spotlight, Dashboard, Automator, iChatAV, and nearly 200 other new features. Tiger appears to be a very good product. However, as with every new operating system, there are a number of incompatibilities with existing software products, drivers, dongles, etc., until developers arrive at Tiger compatibility. Color management seems to have also changed a bit with Tiger. Look below in our Tech Tips section for Tiger tips.
Adobe has released Creative Suite 2 (CS2). CS2 is a dramatic improvement over CS1 and touts easier use and powerful new features. CS2 also has a more consistent and robust color management functionality when moving from Photoshop to Illustrator to InDesign. Plus, you can synchronize your color settings (and other stuff) from one location in Bridge Center, a new centralized file browser. Cool. There is a new 'safe' CMYK color management for InDesign & Illustrator users to ensure the CMYK isn't mishandled. CS2 also ships with a new Euro profile based on Fogra standards. Here are some great reviews from CreativePro.com:
GretagMacbeth just announced a NEW addition to the ProfileMaker v5 suite called PM5 Publish Plus which has all of the features of PMv5 Publish Pro, but includes the MultiColor Module for CMYK+N profile generation. Publish Plus is ideal for expanding the gamut of devices with six additional colors like Digital Printers, Analog Presses, and LFP devices. Publish Plus is targeted at Publishing, Textile Printing and Sign Markets. Furthermore, GretagMacbeth is offering a special introductory value of a FREE Eye-One Pro spectrophotometer and Device Link Module. They've also added an ROI (return on investment) calculator to their site that you will find linked on the following page. For more information:
GretagMacbeth has also released version 3.2 of their Eye-One Match software. This module includes the much-anticipated Digital Camera Module for profiling digital cameras. If you purchased an Eye-One Photo after December 15, 2004, a simple download is all that's required to start using this software (along with free registration):
Fujifilm is releasing a new set of Fuji input/scanner targets. The new Fujifilm Color Targets II are a kit of 5 Fujifilm IT8.7 targets. Four targets are IT8.7/1 (transmissive targets) including 2 35mm format (Velvia, Provia), 2 4x5 format (Velvia, Provia); the 35mm targets are accompanied with batch-read colorimetric data, while the 4x5 targets include custom-measured colorimetric data. The remaining target is an IT8.7/2 (reflective target) made on Fujifilm Crystal Archive Paper (Type DP). Targets are not available for sale individually, only as the complete kit. CHROMiX will be reselling these kits when available.
Hoodman has announced a revolutionary new monitor hood that we hope will start shipping by the end of June. (we're taking pre-orders and will let people know when it starts to ship) This revolutionary new monitor hood will adjust to fit CRTs and Flat Panel monitors from 13" to 23" in size, and works especially well with the Apple Cinema Display. CHROMiX is taking pre-orders now and will make sure you get one of the first ones available. For more information:
Printers are seeing increased printing activity on average as opposed to slowing down. The Printing Business Index (PBI) of the National Association for Printing Leadership (NAPL), the Association's broadest measure of print activity, rose to 60.1 in March 2005, up from 57.8 in February and 59.0 in January. Rising costs are tempering this progress a bit and providing a new challenge. For more:
#1 We asked Don Hutcheson how Fuji's discontinuation of the Velvia 50 film would affect the HutchColor HCT products. Here's what Don said:
1) The method of sampling the curves is flawed by the fact that they do not measure pure dyes, but rather a developed dye image produced by exposing the films with narrow-band R, G and B light. Unfortunately there are no wavelengths that exclusively stimulate each layer without some cross-talk into the others, so the curves for the dye in one layer may well include some residual absorbencies happening in the other layers, which falsely indicate a different color dye.
What ultimately matters is how well a target on one emulsion reproduces images on other emulsions. In my experience a profile made from the current Velvia HCT works very well on a variety of Fuji transparency materials, as well as on other emulsions, like Ektachrome, but this depends a lot on the scanner filter curves.
I have no plans to make a separate HCT on Velvia 100, as I have not seen the need and Fuji 8 x 10 film is getting hard to buy in small quantities"
Thanks for the update, Don!
#2 Greg Exelby pointed out a great on-line article that we thought we'd share with you: PAPER & INK FAQ's, by Sabine Lenz. With all the great proofing technologies available these days, is there still a need for designers to come to press checks? If you are a designer, this is a very valuable read. If you're a printer or broker finding that it's impossible to keep creatives out of the pressroom, this article will highlight the need for taking the initiative to educate your customers about the behind-the-scenes work that goes into their print job. The link:
#3 There is another very good article by Charles Pickett of Publish that discusses a possible new approach to the problems occurring while soft-proofing in variable ambient lighting environments. A must read.
#4 Mac OS X (10.4) Tiger seems to be producing some color-related problems that we are monitoring:
- some users are reporting that ColorSync monitor profiles are not travelling between users when Fast User Switching. If you see this problem, try trashing the "com.apple.colorsync.profiles" files from the "/Library/Caches/" folder. Also, put profiles in the /Library/ColorSync/Profiles folder and they will be available to all users on your system.
- if you are having problems with your HASP-brand dongles under Tiger you may want to download the new drivers:
SHOWS & EVENTS
June 7-9, 2005 IPA Technical Conference, Westin O'Hare, Rosemont, IL. A conference with focus on the latest trends, tools and techniques for graphics professionals. This event will highlight a Color Proofing RoundUP, a Workflow RoundUP, Keynotes from some very notable industry leaders, and a management track as well.
June 12-15, 2005, NAPL & PIA/GATF Sheetfed Pressroom Conference at Marriott O'Hare Hotel, Chicago, IL General sessions and specific seminars will address managerial and technical issues relating to current Sheetfed Pressroom topics and concerns.
June 23, 2005, 6 - 9 PM, Portland, OR. PDF Wine & Tasting Faire, presented by the Pacific Northwest Color Management Users Group. This event focuses primarily on PDF, and secondarily on PDF Color Management issues. Many vendors and consultants will be there, including Adobe's Peter Constable. The event details and location are available at:
July 19-23, 2005, Las Vegas, NV, The Creative Suite Conference. Join leading Creative Suite experts in the largest Creative Suite (CS2) training event of the year.
September 9-15, 2005 PRINT '05 at McCormick Place Complex, Chicago, IL Because of its mammoth size and international presence, PRINT occurs only once every four years and will take the place of GRAPH EXPO and CONVERTING EXPO in 2005.
ColorFAQ - Chromatic Adaptation
First, a few corrections. Thanks to those who wrote in with the "what the..!?" questions.
1. In ColorNews Issue #16 I cut off a sentence mid-way leaving you all hanging... sorry about that. The sentence should have been: "This way he (Joseph Holmes) would bypass the potentially destructive scanner->smaller workingspace or workingspace->workingspace conversions. (he actually went further than this by creating a number of these color spaces which allow shrinking the gamut of an image by simply assigning different profiles)"
2. In ColorNews Issue #17 I incorrectly stated that delta-E stood for delta-Error - I am happy to say that it does not. The E stands for "empfindung" a German word for sensation. Change in sensation makes much more sense!
So, on to this issue's article:
As the color management world works its way toward version 4.x profiles we find that we're getting more and more questions about the differences with v4 profiles and what they mean. One important difference is that all profiles (except device links) are now required to have a 'chad' tag (chromatic adaptation).
So what is chromatic adaptation?
It's probably best to take a step back and talk about how colors are calculated and the different flavors of Lab.
The Lab colorspace (more correctly written L*a*b* but who wants to do that all the time) is based on human perception and is typically calculated from spectral reading curves combined with human eye response curves (observer) and an illuminant (lighting) curve. While we can change the observer and illuminant curves, most Lab colors are based on the 'standard 2 degree observer' and the D50 illuminant curve. To be precise, the flavor of Lab used in Photoshop, ICC profiles and most other publishing cases is the "2 degree, D50" Lab and it's fair to assume that "Lab" written on its own is 2 deg D50 Lab. (it doesn't hurt to ask though)
If all our lighting conditions matched the spectral curve of D50 we'd be set. Unfortunately many don't even come close. In fact, it's impossible to reproduce D50 using any man-made light source! (see my article in issue #14 of ColorNews for more) In most situations, for instance, we recommend calibrating CRT displays to the D65 white point to better match office lighting and sometimes even 5000K light booths (see ColorNews #2). Also, neutral colors printed on inkjet printers achieve their tones by the careful balance of CMYK inks. This balance is calculated for a specific spectral lighting curve and may shift considerably under different lighting (sometimes called metamerism - see ColorNews Issue #5). While we try to build profiles that minimize this effect, sometimes we're better off calculating the color numbers for the profile using a totally different illuminant curve.
ColorNews past issues: Click Here
In order to calculate colors based on a different illuminant, we just substitute the new illuminant curve into the "spectral-reading (times) observer (times) illuminant" equation we use to calculate Lab (it calculates XYZ from which we then calculate Lab). So if we substitute the spectral curve for the D65 illuminant then we get a color number representing the measured sample under the alternate lighting. The important thing here is that it is now '2 degree D65 Lab'. As we rarely change the observer, let's just call it D65 Lab. While this flavor of Lab is quite useful it should never be handed to ICC profiling tools as they typically expect D50 Lab numbers - the ICC spec specifically states that all measurements will be D50 Lab.
So what do we do? Chromatic Adaptation. This series of matrix calculations will convert colors that are relative to one white point (D65) to be relative to a new white point (D50). Without this essential conversion we are handing the profiling software (and the profile, and ultimately the CMM) the wrong numbers and we will probably be disappointed with the result.
"But wait!" you say "if we wanted D50 numbers, why didn't we just calculate Lab using the D50 illuminant in the first place?". The answer, as I hinted above, is metamerism. The spectral makeup of D65 lighting can change the appearance of certain dyes and pigments significantly. So the color we get from calculating Lab using D65 and then adapting it to D50 can be noticeably different than calculating the D50 Lab color directly from the measurement....
Do you see where this leads?
In one calculation we get D50 Lab numbers as illuminated by a D65 light source and in the other, D50 Lab numbers as illuminated by a D50 light source. Now we can correctly calculate delta-E values and assign some numbers to the metamerism / gray balance failure problem we often see! This "metamerism index" can be handy in evaluating inksets and predicting what sorts of problems we're going to see when our gallery-viewed photograph (3500K Solux Lamp) is purchased and moved into an office (6000K fluorescent with nasty spectral spikes).
Another challenging situation is the color data within profiles. As I mentioned above, all measurements within profiles (or handed to profiling applications) are in D50 Lab. If the original measurements were not D50 Lab and were adapted to be D50 Lab then we need to know what flavor of Lab they were originally if we have a hope of reconstructing them. Why would we want to reconstruct them? Well, WE might not but CMM developers might (CMM is Color Management Module, the actual software that converts colors within your applications or OS). We (all of us using ICC profiles) are currently in the age of the "smart profile" and the "dumb CMM". This means that most color conversion smarts are built - hard coded - into profiles. When the CMM converts our colors from one profile to another, it does not do much analysis at all. Most calculations are concerning interpolating colors, which is fairly basic on the scale of things. Future CMMs, however, could do more analysis of the source and destination profiles, image data, etc. In order to do some of these advanced calculations, it can be helpful to be able to reconstruct the original measurement conditions. The 'chad' tag in v4 ICC profiles is required so that any chromatic adaptation calculation that created the profile's colors is documented and available to the CMM if it needs to "back calculate" any colors during its conversions. The good folks at the ICC are hoping that this will help in situations where conversions had broken down in the past.
So we have covered three specific situations where chromatic adaptation may be used:
- converting non-D50 Lab values to D50 Lab for profiling applications
Are you going to use chromatic adaptation in your color pursuits? Perhaps. Most often these calculations will be performed by profiling software on your behalf. If you are doing color calculations for use in profiling software then you may need it. If you are trying to get your arms around metamerism and want to compare measurements under different lighting conditions then you will definitely need it to calculate delta-E values. I've built chromatic adaptation calculations into our upcoming ColorThink Pro software to save you some of the pain of relearning your linear algebra and to do quick metamerism checks. (And yes, I had to relearn my linear algebra.)
At the very least, you now know more about this calculation and when to watch out for incompatible color numbers. You also have new terminology to firmly establish your geek-hood at cocktail parties.
Thanks for reading,
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2 ea used Monaco Optix XR (New $219) $175 <-- price drop
1ea X-Rite DTP-22 Digital Swatchbook (serial) $499 <-- price drop
2ea Fuji (ColourKit) Monitor, RGB Output Profiler & Image Processor software bundle. New. $299
Entire Contents of CHROMiX ColorNews (c)2005 CHROMiX, Inc.