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Author Topic: i1Profiler - i1Pro-uvcut vs. i1Pro-normal does make a difference  (Read 5308 times)
rasworth
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« on: September 03, 2011, 12:36:41 PM »
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One of the first things I did with i1Profiler is create a target on a resin coated paper with moderate OBA content, scanned it with both 1Pro-normal and i1Pro-uvcut instruments, created identical parameter profiles, and made test prints.  I could not tell any difference in the final print, and therefore at the time concluded there was no reason to use the uvcut instrument.

However over time I noticed an occasional light yellowish cast in high mid-tones using the i1normal created profile, that I did not detect during soft proof.  So I went back, re-created the profiles using the latest version of i1Profiler, and this time did a critical comparison of the profiles for soft-proofing in CS5, perceptual mode with "Simulate Paper Color" and "Simulate Black Ink" both checked.  There is a definite difference, the attached image is a screen print of a crop with proofing turned on, using the profile created with the i1Pro-uvcut instrument used in the top half and the one created with a i1Pro-uvnormal in the bottom.

I find that for my setup, for which I've tuned the monitor profile white point and brightness for print matching, that the uvcut version provides a better match.  My conclusion is there is little or no difference in the profile perceptual forward path, but a definite difference in the back path.

Richard Southworth

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rasworth
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« Reply #1 on: September 05, 2011, 10:35:33 AM »
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Obviously my post didn't strike much of a chord with this group.  However if one utilizes softproofing (View > Proof Setup >...) in Photoshop then it is a relevant issue.  Xrite has stated they have enough "magic" in i1Profiler so that one can obtain good print profile results using an i1Pro-normal instrument on papers with OBAs.  And as far as the perceptual/relative forward paths to the printer, i.e. Lab to RGB, it appears to be true.

But scanning an OBA paper (essentially all glossy/semi-gloss resin coated) with an i1Pro-uvcut instrument will result in a significantly different white point recorded in the profile than using an i1Pro-normal instrument.  The different white point will generate a different absolute profile sub-section, and it is the absolute back path, i.e. RGB to LAB, that is used in Photoshop to render the printer colors back to the monitor.  And at least with my eyes and my setup the softproof using a profile generated with an i1Pro-uvcut instrument is more accurate.

Richard Southworth
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TylerB
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« Reply #2 on: September 05, 2011, 10:46:39 AM »
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Hi Richard, I don't think it's that your very useful results do not strike a chord, I just think it's quiet because we're all over at Target and Walmart filling out job applications.
Tyler
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digitaldog
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« Reply #3 on: September 05, 2011, 10:56:16 AM »
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Xrite has stated they have enough "magic" in i1Profiler so that one can obtain good print profile results using an i1Pro-normal instrument on papers with OBAs. 

Where’s that? Seems they have reasons to be building products to measure both ways and have a software package for iSis users to account/adjust for OBAs in their profiles (maybe that’s what you are referring to).

The ‘best’ solution is the most costly: Have one device that measures with and without a UV cut, build a profile both ways. An iSis. One paper’s OBA content may vastly differ from another, so its possible that you could use cut or no cut on one, be just fine, not with the other paper. Of course, how you view those prints play a role.
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Andrew Rodney
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« Reply #4 on: September 05, 2011, 11:32:41 AM »
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The ‘best’ solution is the most costly: Have one device that measures with and without a UV cut, build a profile both ways. An iSis. One paper’s OBA content may vastly differ from another, so its possible that you could use cut or no cut on one, be just fine, not with the other paper. Of course, how you view those prints play a role.
I'm not sure it's fair to say that any approach is 'best.'  While it's cumbersome to use, you can build profiles using ArgyllCMS and address the OBA issue.  You only need a no-cut i1 Pro.  Software is of course free but the learning curve is substantial.
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rasworth
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« Reply #5 on: September 05, 2011, 11:33:30 AM »
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From a recent FAQ in the XRite download section:

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PM5 Optical Brightener Correction -> How to achieve in i1Profiler?

Question: ProfileMaker 5 did include a software-based option for Optical Brightener Correction (OBC) at least for the Perceptual table in a profile. If the software detected optical brightener in the measurement data, a checkbox for OBC was enabled and could be switched on or off. This helped me to avoid color casts in a profile. How can I achieve this with i1Profiler?

Answer: The new i1Profiler software includes a completely new profiling engine, which provides already by default a most neutral gray axis and this effects on all Rendering Intent tables. This has also been confirmed for papers containing optical brighteners.

Additionally, i1Profiler provides a special option to enlarge the range of how far the neutralisation of grays goes into the more chromatic color areas: Profile Settings -> Perceptual -> Neutralize Gray. This allows to increase the neutrality of the gray axis further.
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And I agree with their statement as far as it goes, i.e. a non-uvcut profile seems to render an image to the printer identically as compared to a uvcut based profile.  However, I typically invoke soft proofing on my images and then perform final edits for printing, therefore it's important to me that the back path rendering be as accurate as possible.  And I don't believe they included Absolute in their group of rendering intents.

Red River Ultra Pro Satin measures about -3 on the b axis, Epson Premium Glossy about -4.  Both of these values go close to zero when the paper is measured with an uvcut instrument, resulting in a very different white point, and therefore a different Absolute rendering (for those who may not be aware the Absolute rendering intent is calculated from the Relative intent, using the white point to appropriately bend the curves).  I certainly agree the dual measurement and subsequent calculation using an Isis is the best solution, however there are still a lot of us slogging along with i1Pros, and I believe the uvcut version provides the best softproofing on papers with significant OBAs.

Richard Southworth

Added by edit - Alan, my statements were only in regard to i1Profiler, I agree that OBA compensation, such as I have with ProfileMaker, can do a reasonable job with an i1Pro-normal.


« Last Edit: September 05, 2011, 11:36:02 AM by rasworth » Logged
digitaldog
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« Reply #6 on: September 05, 2011, 11:42:20 AM »
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I'm not sure it's fair to say that any approach is 'best.'  While it's cumbersome to use, you can build profiles using ArgyllCMS and address the OBA issue.  You only need a no-cut i1 Pro.  Software is of course free but the learning curve is substantial.

Yes but how does it deal with the data feed to it when you need uncut data and only have cut data? IOW, how and why isn’t the best approach to gather both kinds of data? OBA compensation is one thing, but its only as useful as the data collected.
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Andrew Rodney
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« Reply #7 on: September 05, 2011, 11:47:54 AM »
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From a recent FAQ in the XRite download section:

------------------------------------------------------------------------------------
PM5 Optical Brightener Correction -> How to achieve in i1Profiler?

Question: ProfileMaker 5 did include a software-based option for Optical Brightener Correction (OBC) at least for the Perceptual table in a profile. If the software detected optical brightener in the measurement data, a checkbox for OBC was enabled and could be switched on or off. This helped me to avoid color casts in a profile. How can I achieve this with i1Profiler?

Answer: The new i1Profiler software includes a completely new profiling engine, which provides already by default a most neutral gray axis and this effects on all Rendering Intent tables. This has also been confirmed for papers containing optical brighteners.

Additionally, i1Profiler provides a special option to enlarge the range of how far the neutralisation of grays goes into the more chromatic color areas: Profile Settings -> Perceptual -> Neutralize Gray. This allows to increase the neutrality of the gray axis further.
------------------------------------------------------------------------------------

All good marketing speak but it doesn’t address anything really. Its fairly obvious there is a totally new profile engine. In ProfileMaker Pro, there was a check box we could see when presumably that profile engine detected OBA’s (and whether cut or non cut spectral data was used should affect this) and the compensation was only available in the Perceptual table. The creation of that table is undoubtably different in both products. The only salient point I can gather from the above text is, the two products are different. In no way does this suggest that either product is such that having a dual mode instrument not necessary nor ideal. Again, my take is, the best solution is to measure both ways and feed that data to the profiler of your choice and examine the results. Then use the profile you prefer. In fact, a better solution is to measure this way and use the OBA module that thus far, can only be used with an iSis due to its mode of capture.
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Andrew Rodney
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rasworth
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« Reply #8 on: September 05, 2011, 12:01:55 PM »
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Andrew,

I'm not disagreeing with you, but my points have to do with those of us who don't have an ISIS, and therefore must do the best they can (again only referring to i1Profiler) with one or the other i1Pros.  I believe XRite overlooked a salient point (softproofing) in their claim that the i1Profiler results tend to be adequate for OBA papers using only an i1Pro-normal.

Richard Southworth
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tony22
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« Reply #9 on: September 05, 2011, 06:11:48 PM »
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In fact, a better solution is to measure this way and use the OBA module that thus far, can only be used with an iSis due to its mode of capture.

And I'll just be running by with my rant about X-Rite not enabling this for i1Pro owners.  Angry
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digitaldog
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« Reply #10 on: September 06, 2011, 04:03:44 PM »
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And I'll just be running by with my rant about X-Rite not enabling this for i1Pro owners.  Angry

They can’t unless you have two units (one cut and one no-cut). They need both sets of data.
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Andrew Rodney
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tony22
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« Reply #11 on: September 06, 2011, 06:36:20 PM »
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They can’t unless you have two units (one cut and one no-cut). They need both sets of data.

Andrew, please elaborate. How could something like PMP do it with a non UV-cut alone but now a newer (better?) package can't?
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digitaldog
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« Reply #12 on: September 06, 2011, 07:06:39 PM »
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How could something like PMP do it with a non UV-cut alone but now a newer (better?) package can't?

OBA compensation (with some assumptions about OBA’s based on spectral data) in ProfileMaker Pro and the newer, far more robust OBA module (that has you print out and adjust the results visually) are not comparable. IOW, ProfileMaker Pro ‘didn’t do it’ the same way or produce the same results. The newer package can do it, it needs the specific data that dual measurements provide.
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Andrew Rodney
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« Reply #13 on: September 06, 2011, 07:10:35 PM »
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The specifics (I’ll let Marc from X-rite’s post on the ColorSync list speak for itself):

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Well hello list,
I saw this little thread about the new optical brightener stuff from X-Rite and just had to jump in. Even though I no longer carry the ol' X-Rite business card, I'm pretty close to the technology and should be able to esplein.

First of all, this is not simple averaging of 2 data sets (shame on you Terry.....and you call yourself a scientist!). Also, this is a far cry from the Optical Brightener Correction that is in PM5. Having been the product manager for that product, I can say that I am 99.9% sure that PM5 applies OBC in the perceptual intent - not the others. Considering that the #1 thing that OBC impacts the most is the reproduction  of paper white (absolute colorimetric), it seems as if the technology was never able to offer the full value of its potential.

I would also add that - even in its "perceptual form", there was no real input for this control. You either got it (or at least had the opportunity to get it) if the software thought you needed it, or didn't If the software didn't think you needed it. All in all, it worked (and works) "sufficiently", but is/was not something built to specifically compensate for the difference between a measured value an the "visual" value of a color, printed on a media, in a specific viewing condition.

So what the heck is different about this new OBC thing. For one, it uses a reference target. Like a color checker. Called a UV checker. It's kinda like a gray balance card. The key is that it doesn't fluoresce. What that means is that colors (grays) appear consistent, relative to the temperature of the viewing illuminant, no matter what type of UV content your viewing illuminant has. A constant, if you will.

The second interesting point is that the correction is specific. The workflow entails printing a target, like an ICC target, and measuring it with the iSis (UV incl+excl). Without giving too much away..... the software crunches the numbers and comes up with a new target that is then printed and compared to the checker, visually (because there's really to way to fully characterize the UV parts of this scenario with instrumentation that either costs less than $30,000 USD or weighs less than 30,000 lbs, or both).

So, as you can imagine, the printed patches look somewhat like the "checker" patches, but vary slightly in color ranging from "this is how it would look with UVin" to "this is how it would look with UVout". The user picks the visual match (or matches) and sets the appropriate params in the software.

At that point, the software will spool up a new set of data for your profiling pleasure. Then, when using this profile to transform your image data, you should see a greater similarity between the colors that the image is supposed to be (what's in the PCS), and what you visually experience.

Rogers's comment is right on the money about the press sheet - it is a 2 step process. Most high quality sheets have limited brighteners, so matching them should not be a big deal. For sheets that do have optical brighteners, you would probably want to run the 2 step process on the press side. Many times, press setups use 2 runs (1st for plate curves, 2nd for press char data), and I suppose that - with some trickery - it could be made to work with no extra "cost".

In any event, it's interesting stuff. If you're working with optically brightened media....it should be especially so.

Also, for those of you who do not know, I have found a home under the umbrella of the Color Management Group. Thanks again to all those who supported me in my short time away.

Best regards,
Marc
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Marc Levine
Color Management Guy
marc@colormanagement.com
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Andrew Rodney
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rasworth
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« Reply #14 on: September 07, 2011, 10:11:36 AM »
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All very interesting, but not directly relevant to my original post.

I'm making a specific claim, for my setup I achieve a better visual match between print and Photoshop softproofing if I create an i1Profiler printer (in my case an Epson 3880) profile for a paper with OBA content using an i1Pro-uvcut instrument, as compared to using an i1Pro-normal.

My criticism of Xrite has to do with their hand-waving FAQ that states i1Profiler software somehow does an ok job on OBA papers regardless of not having an OBA compensation mode.  Fairly obviously the dual scan process using an Isis looks to be technically a good solution, but there are still many of us using only i1Pros and therefore I believe this information may be useful to that community.

Richard Southworth
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digitaldog
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« Reply #15 on: September 07, 2011, 10:34:56 AM »
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All very interesting, but not directly relevant to my original post.

Its relevant in explaining to Tony why its necessary to have dual measurements. The point is, you need both and you need to build the profile both ways and pick the winner. You yourself found this to be true:

Quote
One of the first things I did with i1Profiler is create a target on a resin coated paper with moderate OBA content, scanned it with both 1Pro-normal and i1Pro-uvcut instruments, created identical parameter profiles, and made test prints.  I could not tell any difference in the final print, and therefore at the time concluded there was no reason to use the uvcut instrument.

You later found a preference for one mode over the other. You have two devices, you can build dual measurement profiles (although its more ideal to use the same Spectrophotometer ala iSis). A different paper with differing OBAs may produce opposite results. Bottom line, there’s a reason why some of us measure dual mode and examine the results profile by profile. And then we can tweak farther with the OBC module.

Lastly, it appears you are saying there is no difference in the print but rather the soft proof? Because if so, the area to examine is the preview tables in the profiles.
Quote
My conclusion is there is little or no difference in the profile perceptual forward path, but a definite difference in the back path.

That is something you should ask X-rite about. It doesn’t sound kosher, the two should match in an ideal world. I don’t know that we can attribute this to the instrument data provided (could be a bug in how the tables are being written).
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Andrew Rodney
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rasworth
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« Reply #16 on: September 07, 2011, 11:31:47 AM »
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The difference in the softproofing makes sense to me, assuming I understand what Photoshop is doing.  Creating profiles with the uvcut instrument and the normal version results in profiles with different white points, primarily in the b field.  The Relative gray balance curves appear virtually identical, using either Profile Editor or ColorThink Pro to examine.  However the absolute curves are quite different, since they are derived from the Relative profile sub-section but with a white point adjustment.

If one checks "Simulate Paper Color" in the View menu, then I believe the preview choice from printer space to Photoshop is Absolute, and therefore the normal instrument based profile tends toward blue as compared to the uvcut based profile.  Since I usually perform final edits on my images with softproofing turned on I was often seeing a yellow cast in the final print if I used the normal profile, because I was trying to tune out a bluish cast that didn't really appear in my prints when viewed under my (not very UV rich) illumination.

Richard Southworth
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digitaldog
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« Reply #17 on: September 07, 2011, 11:49:37 AM »
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The difference in the softproofing makes sense to me, assuming I understand what Photoshop is doing.  Creating profiles with the uvcut instrument and the normal version results in profiles with different white points, primarily in the b field. 

Why no difference in the output? The tables should match.

Quote
If one checks "Simulate Paper Color" in the View menu, then I believe the preview choice from printer space to Photoshop is Absolute, and therefore the normal instrument based profile tends toward blue as compared to the uvcut based profile. 


Yes, but again, the two should match.
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Andrew Rodney
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rasworth
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« Reply #18 on: September 07, 2011, 12:35:04 PM »
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No, the absolute curves shouldn't match, and they don't, per my attachment of the neutral rendering curves from both profiles.

As you well know, the normal use for forward absolute conversions is to match the white of one paper onto another for cross proofing, and since the i1Pro-normal instrument is "fooled" by the uv fluorescence the absolute curves show a dropped blue curve (in effect adding yellow ink) to match "real" white.  However Photoshop has seen fit to use the absolute curves for softproofing, in effect trying to match the white of the paper onto the display.  Of course it doesn't achieve a real match, since everything gets rendered up thru the monitor profile, but on a relative basis the difference shows up, per my original post.

The relative/perceptual/saturation curves all converge at the white point by definition, and therefore if one takes a constant image and prints it thru both profiles the result is essentially identical.  It's only when softproofing is employed that the white point difference affects the displayed image.

Richard Southworth

Richard Southworth
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digitaldog
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« Reply #19 on: September 07, 2011, 12:57:30 PM »
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No, the absolute curves shouldn't match

The color appearance should. The soft proof and output should match. You are saying they don’t. What’s going on with the AtoB and BtoA tables?
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Andrew Rodney
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