Luminous Landscape Forum
Raw & Post Processing, Printing => Colour Management => Topic started by: smilem on April 17, 2012, 01:40:23 pm
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Hello, what is suggested workflow for RGB device certification?
I'm unaware of any international standards but perhaps there is some tutorial, workflow etc. for homemade way of doing this?
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Can you be more specific as to what you want?
One can examine the measured output of an RGB device compared to what the profile predicts.
One can compare how the same RGB values output multiple times to define device stability and consistency.
One can compare how the same RGB values differ over the sheet being printed.
All of the above and probably more.
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I was looking for a way to evaluate RGB profiles like a test chart with some "standardized" values, like mediawedge 3.
My current workflow is:
I have opened Media wedge 3 CMYK with Measuretool, and saved LAB data to text file.
I think it is possible to use any test chart or am I wrong?
Then I used colorthink worksheet to load this LAB data and apply my device RGB profile. This gave me RGB/LAB data with my device profile applied to it. I save it as colorlist. As I understand this converts colors and makes sure non printable colors are not there right?
I checked for out of gamut colors by viewing/softproofing the target I made from colorthink colorlist data in PS with my device profile, no out of gamut colors were there.
Then I have made a test chart from these RGB values with Measuretool, open print from PS convert to profile (my RGB profile) print with no color management as I allready converted my test chart to my device profile.
Then I opened my measured data to compare in measuretool and in colorthing worksheet. To my amazement some patches were 4 some 2.5 dE.
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I was looking for a way to evaluate RGB profiles like a test chart with some "standardized" values, like mediawedge 3.
You can use the target you used to build the profile and compare those Lab values to the Lab values the profile actually produced.
You can build your own target too, useful if you want to check more neutrals or if you want to check ‘house’ colors (specific logo colors, skin tones etc).
I’m not sure why you are messing with the Media Wedge CMYK target.
Once you decide what colors you want to compare, you’re going about it the right way using ColorThink. However, ColorThink does NOT convert using Black Point Compensation! So if you want to factor that in (because you are converting using Photoshop), then you’ll have to do all conversions in Photoshop to the patches, sample down (Nearest Neighbor), then load that into ColorThink and build a ColorList there. Then you can compare the reference values to the output values to get a dE report. When you convert in Photoshop, you’ll want Dither off. You also have to decide what rendering intent you want to test. If you always use a Perceptual rendering, you’ll use that to convert the patches using the profile you want to test. Using Absolute gives you a better set of values but if you never use that to convert the data, what’s the point?
Again, you need to consider what you want to run through the profile to compare. You may want to use the iStar target. See: http://www.aardenburg-imaging.com/
Mark hangs out here, he might see this and comment on it’s further usage. If you are using color patches to evaluate that are known to be outside the gamut of the profile, well that’s kind of a waste. So the patches you select can play a role in the dE report you get from ColorThink.
This may fill in the holes I missed:
http://digitaldog.net/files/How_to_compare_deltaE_of_ColorLists.pdf
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Thanks for detailed information on workflow, I have a question:
When I open my target in photoshop (convert to output RGB profile) the Lab values of color picker are different than colorthink shows when I make colorlist from same RGB values. My rendering intent is absolute so BPC is not interfering here.
Colorthink LAB 38.94 19.04 16.82
Photoshop LAB 35 28 30
RGB values are 122 94 69
What LAB to use as reference?
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Do you have the PS eyedropper sampling set to 1x1?
Also again, ColorThink isn’t using ACE although I doubt whatever CMM is used would differ that much. And dither should be off.
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Do you have the PS eyedropper sampling set to 1x1?
Also again, ColorThink isn’t using ACE although I doubt whatever CMM is used would differ that much. And dither should be off.
The photoshop color settings was set to relative, and the color picker used that to convert the data. I changed it to absolute and lab matches with colorthink
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I’m not sure why you are messing with the Media Wedge CMYK target.
That is because PM5 can generate cool reports by itself without third party software, I tried to generate report for RGB device. But somehow I only get error on generating it.
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That is because PM5 can generate cool reports by itself without third party software, I tried to generate report for RGB device. But somehow I only get error on generating it.
I've requested RGB Quality analysis but it's low on the priority scale. The ColorChecker proof and real world printing results are perhaps the next best thing for now.
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What about IT8.7-2 target, references are made by reading printed target on a true rgb device (digital lab), so because digital labs doesnt have widest colorspace but are accurate it is fair that comparing any other RGB printer to these colors is also fair.
I tried making rgb image (srgb.icc as source) from it8.7-2 lab reference and to my amazement best glossy papers like canon pro, and pro printers like ipf8300, canon pro-1, 9000 mk II, can reproduce all colors except last very very black patch acording to photoshop absolute intent. no gamut warning.
Less professional papers, matt papers on same printers (manufacturer profiles were used) does not reproduce all colors. Making any synthetic chart ant converting it to printer profile in ps allows to track icc accuracy, but no standardization there not even possible to compare what a device should reproduce.
Hasn't anyone noticed a need for such standardized target ? Why there is no standardized target to test RGB printers?
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What about IT8.7-2 target...
A dying breed! I think it's all Colorcheckers from here on out.
Hasn't anyone noticed a need for such standardized target ? Why there is no standardized target to test RGB printers?
Not really. Offset press work has a hugely obvious need for specifications like SWOP, GRACOL and FOGRA. With silver halide printers, inkjet printers, etc you just calibrate and profile them and you're off and running. You get what you get. Super easy in comparison. There's not a whole lot of guess work (ie should we calibrate it to this or that specification). On these devices the calibrated state is optimal for that process and there's no variably to it. Coming up with specifications like SWOP is super tedious work that would need to be done by an independent 3 rd party.
Now we could come up with a gamut rating scale for both silver halide and inkjet printers and potentially even have an estimated average value to compare to. That might be fun to work with. That and a graph that shows device drift over time. This is the kinda of thing that might show up in i1P years from now after more pressing issues have been resolved. Or perhaps we'll see it sooner in other software.
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A dying breed! I think it's all Colorcheckers from here on out.
I don't think so, look at attached (PS softproofing screenshots) files the comparison shows brother MFC (small gamut) cheap matt paper, and Canon IPF8300 (large gamut) paper is not cheap ant it is glossy too.
As you can see colorchecker does not allow to see and judge about printer color reproduction, all colors are printable on low gamut printers, while this is good for checking color accuracy it can be done with any colors converted to printer ICC profile.
I was taking about target that would allow to standardize RGB printer print quality, and it is not hard to import data for excel for dE calculation (formulas are available) so custom patches can be evaluated not harder than Fogra charts. It is possible to set custom tolerances for paper color patches and primary solids, grayscale etc.
It also seems possible by using IT8 chart I can chek what printing settings are better, I soft proofed OEM profiles and it clearly shows that a higher print setting on same paper reproduces all patches, when lower print quality setting can't reproduce deep blacks, and some patches.
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Here is the print quality comparison I talked about using IT8.7-2 target the colorchecker can't to do this.
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I said colorcheckers not colorchecker. :-] I expect to see this family moving forward and question the future availability of silver halide IT8 targets. Surely someone can do better than silver halide IT8 targets.... Yes the 24 patch colorchecker has some serious limitations. Repeat your test with the Colorchecker SG though, and see what you come up with.
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The IT8.7/2 is an RGB target without any corresponding XYZ or LAB values. Any reference file you associate with it is an arbitrary choice, and biased toward film. I don't see how that actually gains you anything. While the Color Checker is a subjective, not arbitrary, choice, one does so in part because it has objective ways of evaluating the results in a comparison. You can do it by comparing measurements. Or you can whip out an actual color checker, along with a printed version, and use your eyeballs as the comparator
I think the failure in understanding what you want to do stems from not understanding the difference between commercial printing metrics, and photographic printing metrics. There are such things in commercial printing because of the need for film or file portability: film before CTP platemaking and today for modern workflows it's file portability. These are files transported around that are targeted for a specific kind of printing. In photography, we don't run around with "strike plates" anymore, trying to get them printing in a variety of locations. We tend to work using non-destructive workflows, abstracted from the particular requirements of the print making process.
The point is to print "the image" as best as it can be printed regardless of media or printer used. That's not at all the same requirement for printing presses. There, it's not about printing the best each press can print. It's about printing consistently.
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The IT8.7/2 is an RGB target without any corresponding XYZ or LAB values. Any reference file you associate with it is an arbitrary choice, and biased toward film. I don't see how that actually gains you anything.
Wrong, the values are defined by ISO 12641-1997 standard, you can read them here:
http://www.docstoc.com/docs/25691578/?ct=40&utm_source=docstoc&utm_medium=email&utm_term=Registration+-+Doc&utm_content=Registration+Confirmation+With+Doc+-+DP+-+v2&utm_campaign=Registration&alt=985f1cd6-e30b-4937-91ae-37d268d6db8e
Or you can buy whole standard if you want. Values are not in LAB format but you convert it to LAB without problems.
While the Color Checker is a subjective, not arbitrary, choice, one does so in part because it has objective ways of evaluating the results in a comparison. You can do it by comparing measurements. Or you can whip out an actual color checker, along with a printed version, and use your eyeballs as the comparator
You can do this with IT8.7-2 too printing the target is far cheaper than buying the colorchecker SG, in fact there are numerous sources for IT8 targets that for reasonable prices.
Colorchecker SG does not have 22 grayscale paches to begin with, it also lacks the CMYK RGB step values available in IT8.
The point is to print "the image" as best as it can be printed regardless of media or printer used. That's not at all the same requirement for printing presses. There, it's not about printing the best each press can print. It's about printing consistently.
Agreed.
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Wrong, the values are defined by ISO 12641-1997 standard,
The paper you cite does not say the values are defined in a CIE space. Even if they were, it's absurd, because as anyone who has actually ever looked at targets conforming to IT8.7/2, they are not even remotely the same amongst each other. The paper you cite rather clearly demonstrates this fact.
Or you can buy whole standard if you want. Values are not in LAB format but you convert it to LAB without problems.
OK well if you consider the choice of reference not a problem. I'd consider it a rather significant problem if your goal is to avoid arbitrary decisions and results. You do not have a single reference available here. Period. You have nothing like a TR006 (which correlates CMYK to LAB) that's agreed upon by your industry, nor the equally important issue of tolerances. You can't have the same tolerance for all colors, you realize why don't you?
You can do this with IT8.7-2 too printing the target is far cheaper than buying the colorchecker SG, in fact there are numerous sources for IT8 targets that for reasonable prices.
YOu're not buying an IT8.7/2 either. You're printing it. So why print that target as your control slug to verify the correct output of an "RGB" output device, rather than either the values in the original Color Checker, or Color Checker SG, or some other target?
Colorchecker SG does not have 22 grayscale paches to begin with, it also lacks the CMYK RGB step values available in IT8.
Have you ever seen press process control use 22 grayscale patches? Have you ever seen it use more than 4? Why do you want more? I can imagine some good reasons why, but unless you're really clear about why, you're not really going anywhere.
The fact of the matter is, your industry doesn't have standardized print behaviors like the print industry does. So anything you come up with is somewhere between arbitrary and subjective.
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I have found this site http://www.colorcheck-online.de what do you think about their proposed test chart, methods of quality check for RGB printers?
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There isn't enough information on the site to answer the question. I couldn't readily find a way to download the test chart. The screen shot implies there's sRGB, red, green, blue and if those are sRGB primaries they're going to be out of gamut for a printer on most any media, so that's going to cause huge errors that are almost meaningless. When I click on Tolerances I'm asked to login. So I have no idea what the tolerances are. It might be a reasonable and helpful product for those looking to automate and track process control for fine art printing. And that's probably reasonable.
But the human visual system is a great color comparator. Most people can print a reference image on non-OBA media, stick it appropriate storage, and reprint periodically and compare. *shrug*
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Not all website is available in English, but if you click the English flag then on the right you click "Download" you get test charts.
They are available in various color spaces, the target has smart design:
Row A evaluates gray balance, last 4 patches evaluate Shadow details
Row B evaluates printer accuracy
Row C defines the gamut
They offer 5 uploads for free tests for any so I think I will just upload and see what I get reported.
There is demo account: username: demo password: demo
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Again, you need to consider what you want to run through the profile to compare. You may want to use the iStar target. See: http://www.aardenburg-imaging.com/
Mark hangs out here, he might see this and comment on it’s further usage. If you are using color patches to evaluate that are known to be outside the gamut of the profile, well that’s kind of a waste. So the patches you select can play a role in the dE report you get from ColorThink.
There's an early version of the iStar target that Andrew refers to on the Wilhelm Imaging Research website. You can find it here: http://wilhelm-research.com/istar/index.html
This html page has numerous articles and even some beta software that can calculate I* color and tone values. (note: this software is not for the faint of heart! It was originally developed with color scientists in mind and end-user licensing fees that would pay for advanced training sessions).
I made a newer version of the the target that adds some ordered skin tones and the 24 patch Macbeth color chart to the target page. You can find this newer target at:
http://www.aardenburg-imaging.com/acceleratedagingtests.html
You will need to register on the Aardenburg website (it's free). Then you can download the AaI_testing.zip folder. The color target in this folder is the newer version of the iStar target.
Like Bill Atkinson's visually appealing profiling targets, the iStar target presents a visually ordered set of colors that the human brain can more easily interpret subjectively without resorting to numeric analysis. At the other extreme are scrambled color patch targets that make absolutely no sense to the human observer! In particular the iStar target presents 12 individual hue planes with graduated colors going from dark to light and from low chroma to highest chroma that still fits in gamut within the sRGB colorspace. That is the basic design concept behind the target. Note also that there's a blue color quadrant that shows hues deviating a little bit purple while some are a little more cyanish-blue in color. This is because the LAB colorspace, although very very good in terms of perceptual uniformity, does have some visual non uniformity particularly in the blue hue range. Still, it's the best color model for the human visual system we have at this point in time. This blue-purple deviation within the constant LAB hue plane for blue colors is commonly referred to as the "blue turns purple problem" when trying to use ICC profiles to print out of gamut blues to within gamut. Various profile software packages attempt to correct for this error and other tonal issues in the perceptual tag (by brute force remapping of those LAB colors to other LAB values that look closer to what humans interpret as a constant blue hue over varying chroma and lightness levels), Nonetheless, the iStar target presents this blue LAB hue plane to the output device to evaluate how it renders.
The I* (iStar) metric is too complex a subject to present here in extensive detail, but I will try to explain some basics, anyway. The concepts of this I* metric are really important for printmakers and for any application where color and tone reproduction is being evaluated. The I* metric has both a contrast function and a chroma weighting function. Both functions are hugely important when evaluating photographic tone reproduction. Delta E does not correctly weight chroma within the context of a complex scene (i.e., humans prioritize low chroma colors to identify scene color balance) nor can Delta E rate global or local changes in image contrast whereas the I* metric does both. The I* metric also evaluates overall tone and color reproduction in a meaningful way even when there are large color matching errors involved, i.e, which is almost always the case when trying to reproduce a larger dynamic range image onto a reflection print medium with much smaller printable dynamic range. Here's a classic example: You have an RGB 0,0,0 black value in your image file that is tagged with a working space profile as L* = 0, but you are printing to a matt fine art paper that can only make a black no darker than L* = 15. Even if you reproduce the a* and b* = 0 values perfectly on paper, you are still left with a delta L* discrepancy of 15 under best case scenario. Thus, the delta E error will also be 15, ie., a huge color matching error. What this all means for photographic prints is that average delta E errors will be huge in many circumstances when comparing image file to print (or even monitor color to print). So, how do we perceive a satisfactory color and tone reproduction on any reflection print? That's where the I* metric comes into it's own. It evaluates proportional color and tonal response which is also what humans do when looking at reflection prints. Optimum tone reproduction occurs by keeping relationships between various colors and tones in the image relatively proportional when they can not be exact. Thus, the I* metric can successfully evaluate large color and tonal changes on an easy-to-understand percentage scale whereas delta E just generates huge error values when exact color matching can't be reasonably accomplished.
The concepts I just discussed may be better grasped if you also decide to read the following paper (and other articles) on the Aardenburg Imaging website:
"Case Study #1 Evaluating the Influence of Media on Inkjet Tone And Color Reproduction With the I* Metric" (http://www.aardenburg-imaging.com/cgi-bin/mrk/_4625ZGxkLzBeMTAwMDAwMDAwMTIzNDU2Nzg5LyoyMA==)
Although the iStar target that Digitaldog kindly mentioned in this thread is indeed a very useful generic test target designed to exercise the I* metric's color and tone algorithms effectively, the I* metric can also be used to evaluate color and tone reproduction in essentially any image. The paper just cited shows a case where a specific pictorial image was subsampled to make a custom color target which could then be read on a standard spectrophotometer. The image and the custom target were then taken through a tone reproduction exercise on three different paper types, one glossy, one mat,and one plain paper using the same printer and inks. I hope you find the I* scores for the different papers interesting.
What remains to happen for the I* metric is more interest to be shown by the color and imaging science community and the printing industry. With such interest we could produce some software apps that will make it easy for a wider audience to use the I* metric on a practical basis. Modesty aside, the I* metric is a powerful analytical method for color and tone reproduction accuracy problems, but much to my surprise, it has been essentially ignored by the color and imaging science community and by the printing industry even though it's open source and was published more than five years ago in the NIP20 conference proceedings of IS&T. I would think the printing industry in particular would welcome a much better algorithm with a familiar percentile scale to better communicate color and tonal accuracy issues with customers. They have customers who often wonder why their digital files don't print exactly like they look on a monitor and then blame the print shop.
Time will tell if the I* metric eventually finds an interested audience.
Other technical articles on the I* Metric are also available on the documents page of the Aai&A website:
http://www.aardenburg-imaging.com/documents.html
Sorry for the long-winded post, but you can blame Digitaldog for mentioning iStar ;D
kind regards,
Mark
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There's an early version of the iStar target that Andrew refers to on the Wilhelm Imaging Research website. You can find it here: http://wilhelm-research.com/istar/index.html
This html page has numerous articles and even some beta software that can calculate I* color and tone values. (note: this software is not for the faint of heart! It was originally developed with color scientists in mind and end-user licensing fees that would pay for advanced training sessions).
What will the software cost be?
I have downloaded the beta and it has a bug that there seems to be scroolbars missing in nearly every window, if monitor size is small you don't even expect you can't see all the controls on the window.
I made a newer version of the the target that adds some ordered skin tones and the 24 patch Macbeth color chart to the target page. You can find this newer target at:
http://www.aardenburg-imaging.com/acceleratedagingtests.html
You will need to register on the Aardenburg website (it's free). Then you can download the AaI_testing.zip folder. The color target in this folder is the newer version of the iStar target.
Will this newer target work with the software on Wilhelm Imaging Research website?
Why isn't there a LAB reference to the image? I mean to read it with my device I need to re generate it for i1Pro. for i1isis etc.
or I need to manually do so from http://wilhelm-research.com/istar/tutorials/data_templates.zip does this spectral file is the reference for the istar target?
You have an RGB 0,0,0 black value in your image file that is tagged with a working space profile as L* = 0, but you are printing to a matt fine art paper that can only make a black no darker than L* = 15. Even if you reproduce the a* and b* = 0 values perfectly on paper, you are still left with a delta L* discrepancy of 15 under best case scenario. Thus, the delta E error will also be 15, ie., a huge color matching error.
I understand why iStar is better than delta E calculations but haven't said what is you opinion about www.colorcheck-online.de and their target?
What remains to happen for the I* metric is more interest to be shown by the color and imaging science community and the printing industry. With such interest we could produce some software apps that will make it easy for a wider audience to use the I* metric on a practical basis. Modesty aside, the I* metric is a powerful analytical method for color and tone reproduction accuracy problems, but much to my surprise, it has been essentially ignored by the color and imaging science community and by the printing industry even though it's open source and was published more than five years ago in the NIP20 conference proceedings of IS&T. I would think the printing industry in particular would welcome a much better algorithm with a familiar percentile scale to better communicate color and tonal accuracy issues with customers. They have customers who often wonder why their digital files don't print exactly like they look on a monitor and then blame the print shop.
Why hasn't anyone made a xls file to load and calculate the istar metrics ? that would be awesome, the Wilhelm Imaging Research software is beta but it seems very complicated in that you do not need every piece if info it shows you, there is no clear workflow to even test the program. No reference file to read data on i1Pro, i1isis, barbierri etc.
I kind of like software products and off line methods of doing things, while somebody else might prefer to to it online internet access is not always available or is reliable. So offline sollution will always be better in my mind.
Sorry for the long-winded post, but you can blame Digitaldog for mentioning iStar ;D
kind regards,
Mark
I have learned so much thank you.
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What will the software cost be?
I have downloaded the beta and it has a bug that there seems to be scroolbars missing in nearly every window, if monitor size is small you don't even expect you can't see all the controls on the window.
Will this newer target work with the software on Wilhelm Imaging Research website?
I'm no longer involved with the WIR staff on any projects. You'd have to contact WIR if you want to experiment with the WIR iStar software.
Why isn't there a LAB reference to the image? I mean to read it with my device I need to re generate it for i1Pro. for i1isis etc.
or I need to manually do so from http://wilhelm-research.com/istar/tutorials/data_templates.zip does this spectral file is the reference for the istar target?
I got another similar request for this offline, so let me work on it this week. I will post a zip folder with a 1 pixel/per patch image of the newer iStar target plus .txt and color exchange files (the two formats Logo Colorlab can export). I am not up to speed on Colorport (I'm still using Measuretool and Logo Colorlab with Spectrolino/spectroscans), but I seem to recall that Colorport can import 1 pixel/patch files and do a nearest neighbor upres to generate iSis and i1Pro readable targets. Otherwise, the exported text files might also get you to your objective. Colorport will no doubt reorder the patches to work with the corresponding patches, so you will also want to make a non-rerarrange print of the iStar target pattern so that it's "human readable". Its 12 ordered hues and ordered skin tone quadrants plus grey ramps make for a great visual assessment of profile output quality. Also, good to compare one's visual evaluation of the printed target quality against the calculated I* scores.
I understand why iStar is better than delta E calculations but haven't said what is you opinion about www.colorcheck-online.de and their target?
That site's English version is only partially enabled so I haven't worked with this software (my understanding of German sadly lacking), but it looks like it has you print selected spot colors and tracks delta E variations, etc. Delta E and other LAB analyses are great for process control, so if the goal is to keep a printer tightly process controlled, then I feel these types of "colorcheck" approaches have merit, perhaps even superior to the I* metric as a process control tool. The I* metric was designed to provide answers on a more fundamental level. Say you have an image file that has already been edited to give a "master file" with very pleasing image color and tone (maybe not accurate to original scene, but what the customer wants in the image and ideally in the subsequent print). The master file LAB referred data then becomes the color and tone aimpoint for the optimum reproduction. The I* will generate a color and tonal accuracy number on a percentile scale. It's easier for non color geeks to understand when you say, "this print has 88% color accuracy and 90% tonal accuracy when this image is expertly printed on this printer/ink/paper combination A, but if you want to print on paper B, it has lower color gamut and therefore best reproduction will drop a little to 82% color retention (hue and color) and 85% tonal retention (lightness and contrast)". That's the basic idea behind the I* metric.
I'm also using the I* metric at AaI&A to track and report light fading at increasing exposure doses where the reference print is an AaI&A 30 patch standard color target, and the I* metric is used to track the fading as it progresses. So, at time = 0, no fade has occurred. I* color = 100% and I* tone = 100 %, and delta E would be simple as well, i.e., equal to 0.0. But as fading progresses, average delta E values become quite large and thus go beyond what is considered perceptually valid, but iStar will keep reporting meaningful color and tonal accuracy scores. Check out any of the test reports in the AaI&A database to see these principles in action. You may, for example, notice that HP Vivera pigments are quite well fade-balanced on many media (HP chemists are masters at creating fade balanced ink sets!), so I* color and I* tone usually drops more or less uniformly as fading progresses, whereas Epson Ultrachrome inks, for example, show significantly more I* color change while I* tone remains relatively high as fading progresses. This is because the Epson yellow typically fades more rapidly than magenta or cyan, but yellow adds little to overall image contrast yet much to color balance, hence, I* color dropping faster than I* tone. You can ascertain these differences in faded appearance quite easily by looking at the faded test results shown in the reports (I generate the faded color reproduction in the reports directly from the measured LAB data), and by the I* scores, but not by the delta E values which I also report since so many people are accustomed to delta E.
Why hasn't anyone made a xls file to load and calculate the istar metrics ? that would be awesome, the Wilhelm Imaging Research software is beta but it seems very complicated in that you do not need every piece if info it shows you, there is no clear workflow to even test the program. No reference file to read data on i1Pro, i1isis, barbierri etc.
I kind of like software products and off line methods of doing things, while somebody else might prefer to to it online internet access is not always available or is reliable. So offline sollution will always be better in my mind.
I've gone under the general assumption that if other color scientists got interested in the I* metric, they would program their own spreadsheets from the equations available in the technical paper. That said, I do use Excel to make the I* calculations, but my .XLS files have proprietary stuff in them as well, so it's been on my to do list for a long time to create a generic iSTAR XLS spreadsheet and make it available to others. Wasn't high on my priority list since no one to date had shown any interest ;)
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I will post a zip folder with a 1 pixel/per patch image of the newer iStar target plus .txt and color exchange files (the two formats Logo Colorlab can export). I am not up to speed on Colorport (I'm still using Measuretool and Logo Colorlab with Spectrolino/spectroscans), but I seem to recall that Colorport can import 1 pixel/patch files and do a nearest neighbor upres to generate iSis and i1Pro readable targets.
Once you have the single pixel per patch TIFF, if you have ColorThink Pro, it can build a ColorList. That list can then be imported into ColorPort. ColorPort should honor the order (or I believe you can drag them into a different order within the Import dialog).
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Once you have the single pixel per patch TIFF, if you have ColorThink Pro, it can build a ColorList. That list can then be imported into ColorPort. ColorPort should honor the order (or I believe you can drag them into a different order within the Import dialog).
Thanks Digitaldog. Folks, give me a day or two to get this folder together. Not sure everyone wanting to try this target has ColorThink Pro, but let me know once I post if we have met the basic need for measuring with other instruments. I'm still on the grand old spectrolinos...slow but steady and will read the target in its non rearranged order.
cheers,
Mark
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That said, I do use Excel to make the I* calculations, but my .XLS files have proprietary stuff in them as well, so it's been on my to do list for a long time to create a generic iSTAR XLS spreadsheet and make it available to others. Wasn't high on my priority list since no one to date had shown any interest ;)
If you could make such xls file available then it would no doubt make iStar more usable, as not everyone who can use it and provide feedback knows how to calculate dE and other formulas in excel etc. Photographers are not programmers.
You mention that your formulas are developed by color scientists.
The German website has one interesting thing too, they calculate the reference grayscale from "by patented algorithm" and then calculate "delta s" as "DIN 55981 - Determination of relative hue of near white specimens." So that means the measurement grayscale values are compared against adapted grayscale reference values based on paper white.
I wonder how reliable this is or how this can be done, I mean how can you calculate and compare measured values against some synthetic values that are adapted to already measured ones, sounds very complicated.