OBC functionality in iProfiler is VERY BADLY programmed! how to bypass?

[Tim Lookingbill]

Thanks, Robert, for the Northlight link.

That cleared up a lot in my understanding of what to look for and test within a printed sample. Those visual yellow/blue neutral patch testers in Keith's review photos on OBAs under different lights seems to support why I have to apply a reduction in the blue channel in Level's middle slider in Photoshop to get a better color match to my display.

Epson Ultra Premium Glossy appears at times depending how long I'm away from my 6500K display neutrality to be quite bright white just like my display. Lengthy edit sessions on the display don't change my perception of how blue this paper appears until I view it under my 5000K-ish daylight flotubes where it then appears warmer but the rest of the tonality of prints does appear bluer without the Level's blue channel reduction.

At least I get an idea of what and how all this needs to be done though I'm sure not as exacting as it should be based only on my visual observations.

[GWGill]

If I understand you correctly, you are saying that the dual scan would give you a better way of computing the spectrum due to the OBA. Why would you need to measure anything except the paper white for that?

Because the exact way that the incident UV and resulting blue light is filtered by the colorants in and on the medium is better measured than estimated, if you have the means to do so.

When you say 'quantum efficiency', what do you mean?

Technical term for how efficiently the fluorescent agent converts photons of UV into visible light.

If that is what you mean, then would this not be quite useful in correcting the full gamut?

Useful, but not essential. Given a spectral model of the Fluorescent agent, it's possible to then combine that with a model of how the colorants affect the media spectral reflectance, and arrive at a model of FWA augmented reflectance that accounts for the major effects. Naturally this variable correction applies to any color.

If you like, I can send you a copy of my 2003 paper on Argyll's FWA compensation. It's technical (and I have made refinements since then), but it conveys a lot of the essential logic of what it does.

[Robert Ardill]

Epson Ultra Premium Glossy appears at times depending how long I'm away from my 6500K display neutrality to be quite bright white just like my display. Lengthy edit sessions on the display don't change my perception of how blue this paper appears until I view it under my 5000K-ish daylight flotubes where it then appears warmer but the rest of the tonality of prints does appear bluer without the Level's blue channel reduction.

I don't have the Epson Ultra Premium Gloss, but I would expect it to have quite a high OBA content, based on doing some tests, which you can see here:



(right-click to view full size).

These are some papers I have lying around. The spectrum is plotted using the Argyll spotread utility.  I've added some notes, based on my interpretation (which may not be entirely correct).  At any rate, if I'm half-right, then you can see that most of the glossy and satin papers have quite a bit of OBAs (hump around 440nm), and most seem to have some shading agents (wide dip around 600nm).  

I see that I've noted that the Hahnemuhle PhotoRag Ultrasmooth has no OBAs which isn't correct, but it doesn't have much.

In general the matte papers have little or no OBAs, the notable exceptions being the Hahnemulhle PhotoRag Bright White and Epson Archival Matte.

Robert

[Robert Ardill]

Given a spectral model of the Fluorescent agent, it's possible to then combine that with a model of how the colorants affect the media spectral reflectance, and arrive at a model of FWA augmented reflectance that accounts for the major effects. Naturally this variable correction applies to any color.

If you like, I can send you a copy of my 2003 paper on Argyll's FWA compensation. It's technical (and I have made refinements since then), but it conveys a lot of the essential logic of what it does.

Thank you for the clarification.

If the paper is this one: "A Practical Approach to Measuring and Modelling Paper Fluorescence for Improved Colorimetric Characterisation of Printing Processes" then I've already purchased it.  But I would be interested to see the refinements and I'm sure others on this forum would like to read it.

Robert

[GWGill]

If the paper is this one: "A Practical Approach to Measuring and Modelling Paper Fluorescence for Improved Colorimetric Characterisation of Printing Processes" then I've already purchased it.  But I would be interested to see the refinements and I'm sure others on this forum would like to read it.

Yes, that's the one. The refinements are implementation detail - they wouldn't change the paper very much, even if I updated it, but they are reflected in the source code and behavior.

[narikin]

These are some papers I have lying around. The spectrum is plotted using the Argyll spotread utility.  I've added some notes, based on my interpretation (which may not be entirely correct).

Robert

Reading through this thread, as an owner of an iSis and i1Profiler, I wondered why my Canson Platine profile performed so well compared to others I had tried, some low-OBA papers, even with dual measurements.

I agree with you Robert that Platine is a 'magnificent paper', assuming you can embrace the warm white. I can and do. It is my #1 choice wherever possible.

[Robert Ardill]

Reading through this thread, as an owner of an iSis and i1Profiler, I wondered why my Canson Platine profile performed so well compared to others I had tried, some low-OBA papers, even with dual measurements.

I agree with you Robert that Platine is a 'magnificent paper', assuming you can embrace the warm white. I can and do. It is my #1 choice wherever possible.

Yes, it's interesting to look at the spectrum response of these papers to see if this partially explains why we like some papers better than others.  A paper that surprised me was the HP ID Satin - I have a roll that's been lying around for a few years and I didn't really consider it for anything more than proofing, but when I had another look at it I found that it's a really good heavy paper with a fine satin finish.  Prints on it look good in pretty much any light ... and that's explained by the low amount of OBA in the paper.  The paper also has a good white look, which is probably party due to the shading agents (as well as the relatively small amount of OBAs).

But I guess the main use of the spectrum plots is as a warning when using some papers: the Permajet Oyster, for example, really shouldn't be used unless the target illuminant is known.

Robert

[Tim Lookingbill]

Was hoping someone could show what is considered an unacceptable print due to OBA's vs one without viewed under a light that makes them unacceptable. I can't find anything online to show me this.

I examined my mid '90's commercial press paper sampler from Potlatch and see that their papers have a slight yellowish amber (off white) tint next to my quite brilliantly brighter, bluish, less dingy Epson Ultra Premium Glossy viewed under the same lights I demonstrated previously.

The Potlatch sampler may have aged but then I didn't have the Epson paper to compare against as a new standard for white back then.

[Alan Goldhammer]

Was hoping someone could show what is considered an unacceptable print due to OBA's vs one without viewed under a light that makes them unacceptable. I can't find anything online to show me this.

There's a lot of data on the Aardenburg website showing the effects of OBAs on paper white and the various colors following prolonged fading studies under illumination.

[Robert Ardill]

Was hoping someone could show what is considered an unacceptable print due to OBA's vs one without viewed under a light that makes them unacceptable. I can't find anything online to show me this.

I examined my mid '90's commercial press paper sampler from Potlatch and see that their papers have a slight yellowish amber (off white) tint next to my quite brilliantly brighter, bluish, less dingy Epson Ultra Premium Glossy viewed under the same lights I demonstrated previously.

The Potlatch sampler may have aged but then I didn't have the Epson paper to compare against as a new standard for white back then.

Hi Tim,

I think what you're looking for is very subjective - what may be acceptable to one person may not be to another.  Also it's not possible to get two papers with identical characteristics, one with and one without OBAs (obviously .

On the other hand, it's pretty easy to show the color shifts due to UV on a paper that has OBAs.  Just illuminate the print with a light that has low UV (for example a Solux 4700K bulb) and then shine some UV on it using a UV torch (costs a few dollars only).  If the print is on a paper that has no OBAs, the UV light will make no difference.

Once you can see what the UV does on a print that has OBAs, you could then view the print under blue sky daylight (which has plenty of UV) to see the effect.

A simple test to see if the paper has OBAs is to shine UV onto it in a totally dark room: the paper will look blue.

What would be more interesting really would be to do a print (on a paper that has OBAs) with no OBA compensation, then reprint with OBA compensation for a specific illuminant (which is known to have UV), and then view both under this illuminant.  It's something I intend to do when I have some spare time ... not going to be soon though!

Robert

[Tim Lookingbill]

There's a lot of data on the Aardenburg website showing the effects of OBAs on paper white and the various colors following prolonged fading studies under illumination.

I'm aware of OBA's and what they look like on blank, non-printed paper.

What I'm trying to get an idea from visual inspection is how OBA's cause color prints to look unacceptable and unappealing to the point it must be measured and profiled to improve the color or avoid the OBA paper all together. What would be even more helpful is to show a comparison of how OBA's actually change the look of color ink on paper vs how it's not changed on non-OBA paper.

Has anyone actually researched this with visual comparisons to show the benefits of avoiding printing color images on OBA paper or measuring and profiling to fix it?

I gather from the answers in this thread and what I see online no one is that concerned about it enough to show what this looks like. I'm trying to get an idea of just how subtle the effects are and see how technology such as a print profiling package can improve the results.

I'm also assuming that there are non-OBA papers that look just as bright pure white (like the Epson Ultra Premium Glossy) as ones with OBA's so the advice to avoid OBA paper will still not cause one to settle for printing on dingy looking, off white paper as I see in the Potlatch sampler.

Robert, I look forward to your research and the results on this issue.

[Robert Ardill]

Has anyone actually researched this with visual comparisons to show the benefits of avoiding printing color images on OBA paper or measuring and profiling to fix it?

I gather from the answers in this thread and what I see online no one is that concerned about it enough to show what this looks like. I'm trying to get an idea of just how subtle the effects are and see how technology such as a print profiling package can improve the results.

I agree that it would be very useful to have tests that show the hue changes on a variety of papers that have OBAs under illuminants with different amounts of UV.  But this could end up becoming a life's work ... and an expensive one at that.  One would need a controlled environment, and it's not just the papers and the light, but also the inks (and how opaque) and profiles and printers.  Then there's the problem of how to measure and report that information, not a trivial task either!. That's why avoiding papers with OBAs may be a smart move, or keeping to papers that have low OBAs.

One thing I do know is that the effect of lighting on pictures is huge ... even on papers that have no OBAs.  I suspect that the 'answer' is a sort of recipe: for example:

High OBA Paper; Light: High UV, Cool White
  OBA compensation
  Warming filter
  Taste and adjust seasoning

No OBA Paper;  Light: Cool White
  Warming filter
  Taste and adjust seasoning

The other thing is to use few papers and get to know how they perform well.
 

I'm also assuming that there are non-OBA papers that look just as bright pure white (like the Epson Ultra Premium Glossy) as ones with OBA's so the advice to avoid OBA paper will still not cause one to settle for printing on dingy looking, off white paper as I see in the Potlatch sampler.

I would be VERY surprised if the Epson Ultra Premium Glossy doesn't have quite a lot of OBAs Tim.  If you look at the Epson paper specs you'll see that they don't specify whether or not this paper has OBAs; however when a paper has none then they do state it (for example for the Exhibition Watercolor Paper Textured).  It's the same for other paper manufacturers.  So when the OEM/manufacturer does NOT specify that the paper has no OBAs, you can be pretty sure that it does.  The only way I know of gauging how much is to measure the SPD as I've done with the sample set above.


Robert

[Tim Lookingbill]

I agree that it would be very useful to have tests that show the hue changes on a variety of papers that have OBAs under illuminants with different amounts of UV.

I did not suggest this in my previous post at all.

I said one test to show how a printed color image whose appearance is affected by OBA paper viewed under any normal viewing light and how it appears being corrected or improved upon either by profiling or switching to printing the color image on a non-OBA paper. This would not be an expensive test to demonstrate this issue IMO.

Your suggestion that overall there are too many variables to consider in mitigating against this and the solutions offered makes futzing with this pretty much similar to taking a humidifier to the beach to dry out the air. It's a no win situation that's not worth the trouble of fixing. Of course every color print on any given paper will look drastically different under a variety of lights, but we don't make prints so they will be viewed under every light under the sun. That would be unmanageable and pointless.

I would be VERY surprised if the Epson Ultra Premium Glossy doesn't have quite a lot of OBAs Tim.

Sorry, I didn't write that clear enough. I know the Epson paper has OBA's>(I couldn't see its effect in the photo I posted previously). I mentioned it now as a comparison to how bright white it is compared to the 20 year old Potlatch paper sampler whose warm, yellowish amber off white is not a desirable look. The point I was making is that as long as there is something to compare against no "white" paper is going to exhibit the exact hue as intended which creates even more variables.

I still have no answer on how OBA paper changes the look of printed color viewed under any given light.

[Stefan Ohlsson]

I still have no answer on how OBA paper changes the look of printed color viewed under any given light.

Isn't the change of paper whiteness over time an even more important factor not to choose papers with OBA:s? The Epson Exhibition (here in Europe called Epson Traditional) changes its hue to a yellow-greenish tone, quite unattractive.

Stefan
www.korta.nu/profiler

[JRSmit]

I still have no answer on how OBA paper changes the look of printed color viewed under any given light.

Tim, as part of the review work i did on the Hahnemuhle Photo Pearl, i tried to address that specific aspect. To summarise: The change to the perception is mainly dependent on 2 aspects, assuming a given print( so a constant in this test): the spectrum of the light, and its UV content. In my perception looking at prints, the combination of both aspects can vary from cool (f.i direct sunlight or even blueer the light from a blue sky) to warm (a ordinary halogen) and warmwith a cool touch  ( a ordinary warm white LED) to the lighter parts (less ink) of a print.
A great way to test this is to take this OBC print from i1Profiler with its 4 columns of grey, and find a visual match with the testchart under every possible lighting condition you can get. Score the matching results, and you will see it can go all over the OBC print.

[Robert Ardill]

Isn't the change of paper whiteness over time an even more important factor not to choose papers with OBA:s? The Epson Exhibition (here in Europe called Epson Traditional) changes its hue to a yellow-greenish tone, quite unattractive.

Stefan
www.korta.nu/profiler

Good point ... and one I hadn't thought of.  Here's an article that talks about both OBAs and the Epson Exhibition: http://www.luminous-landscape.com/reviews/printers/epson_exhibition_fiber.shtml

Robert

[Robert Ardill]

Of course every color print on any given paper will look drastically different under a variety of lights, but we don't make prints so they will be viewed under every light under the sun. That would be unmanageable and pointless.

Well really this is the whole point of not using papers with OBAs.  As long as there is some white showing chromatic adaptation will to a large extent compensate for the different light sources as all the colors will shift proportionally.  Admittedly, very spiky illuminants will mess this up ... but then we shouldn't be viewing prints under these lights.

With OBAs the shift in colors will not be proportional, so the relation between the colors may be badly affected.

My own feeling is that we can spend ages trying to pin this down, but the best solution is to use papers with no OBAs, or papers with very little OBAs.  There are some really excellent papers available now with great gamut and DMax, so why use papers with OBAs?  In my case, the only paper I use which has a fair amount of OBAs is the Canson Photo HiGloss ... and the only reason I use this paper is that I need a very smooth, heavy, gloss paper to laminate under acrylic.  If anyone knows of a really good, very smooth, thick, opaque gloss paper with no OBAs I would be VERY grateful!

Robert

[Ernst Dinkla]

With spectrometers that either have a UV cut filter or no UV light source at all, any compensation in the profile for OBA effect  has to depend on an extrapolation from the spectral plot above the wavelengths said spectrometers can not measure. Enough meters that do not measure below 430 nm wavelength. A tricky method given the differences in OBA content between papers and differences in their whiteness.
The suggested measuring of the UV absorbance should on the other hand take into account that TiO2 whitening agent absorbs UV light too but its fluorescence does not occur in visual light but heat.

The safest way would be measuring with a non-UV cut spectrometer on OBA less papers. For a more predictable profile result, reduced color inconstancy in practice and more color constancy in time.

Met vriendelijke groet, Ernst

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
November 2014 update, 680+ inkjet media white spectral plots

[Tim Lookingbill]

...In my perception looking at prints, the combination of both aspects can vary from cool (f.i direct sunlight or even blueer the light from a blue sky) to warm (a ordinary halogen) and warmwith a cool touch  ( a ordinary warm white LED) to the lighter parts (less ink) of a print...

Again to clarify even further, are you just describing your perception of the change of hue to paper white ONLY or are you including the hue changes in the entire color image as well?

Did you look at the photo I posted of the white rose on OBA ridden Epson Ultra Prem Glossy and figure out whether the light or the OBA reacting to the light created all those paper white hue changes? Keep in mind that as long as you view that print under changing light and are able to compare them side by side as depicted in my photo, you'll ALWAYS see a change to hue to every paper manufactured whether it has OBAs or not.  

Isn't the change of paper whiteness over time an even more important factor not to choose papers with OBA:s? The Epson Exhibition (here in Europe called Epson Traditional) changes its hue to a yellow-greenish tone, quite unattractive.

I have never seen that effect exhibited in all the papers I've come across in my entire 55 years. I've got paper items in my illustrators/graphic design portfolio that go back as far as the early '80's and published pieces as far back to the early '70's in my high school days that only slightly yellowed. In all those years I was never told to be concerned about OBA content for archival purposes as an artist. My Epson Ultra Premium Glossy inkjet prints have been hanging on my living room wall exposed to all forms of low level light for at least 5 years with no change to paper white or the ink.

So it's obvious that Epson Exhibition is one rare bird and should be avoided if it turns yellow-greenish over time. I don't know how anyone is going to be able to predict that will happen to any one particular OBA paper. I'm not worried my Epson Ultra Prem Glossy prints are going to turn yellow-greenish seeing 50 years from now, it'll be just as easy as it is now to do a reprint on better or different paper.

[Tim Lookingbill]

With OBAs the shift in colors will not be proportional, so the relation between the colors may be badly affected.

I'm assuming you're referring to the relationship of the entire color image and paper white and not just the paper white, and if so, I'ld like to see a demonstration of this disproportional bad color relationship.

I have not seen this happen in any painting, color pastel drawing on paper or print of an image in all the paper media I've viewed in my lifetime as an art director/prepress production technician/graphic artist/illustrator/cartoonist.