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Author Topic: Why OBAs in this paper?  (Read 6892 times)

rasworth

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Why OBAs in this paper?
« on: March 11, 2018, 11:55:16 am »

Needed an inexpensive 17"x25" photo paper, purchased a box of Red River UltraPro Luster 300.  Checked it with the black light, as expected had significant OBA content.

I created a profile using I1Profiler, auto generated 1215 patch set, and my I1Pro UVCut.  Profile checked out ok, satisfactory test print and good match via Photoshop softproofing.  White point per ColorThink Pro is L*a*b* = 94.1,-.8,-.6.

So here's the question - the white point after supposedly filtering out the uv OBA excitation is close to neutral.  Why is the manufacturer using OBAs at all?  Is there some magic outside of the uv excitation that contributes to the whiteness, or has the manufacturer decided really bright is better than white?

I did a quick spot measurement with my I1Pro Normal, L*a*b* = 95.6,.9, -8.0, the OBAs are obviously there and kicking.

Richard Southworth

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Mark D Segal

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Re: Why OBAs in this paper?
« Reply #1 on: March 11, 2018, 12:08:59 pm »

b* of -8.0 is hardly near neutral - it's quite bluish. But to address your question: manufacturers include OBA in some of their papers for the same reason that soap companies sometimes put whiteners in laundry detergent - it's for those "whiter whites" that large numbers of consumers like.
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Mark D Segal (formerly MarkDS)
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rasworth

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Re: Why OBAs in this paper?
« Reply #2 on: March 11, 2018, 12:23:07 pm »

I understand b* = -8.0 is quite bluish, but -.6 is not, and that is the result using the uv cut instrument.  So can we assume the base "whiteness" of the paper before adding OBAs is reasonably neutral?  Or another way of looking at it, some years later after the OBAs have lost their uv excitation capability will the paper appear neutral instead of yellowish?

Richard Southworth
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Doug Gray

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Re: Why OBAs in this paper?
« Reply #3 on: March 11, 2018, 12:30:11 pm »

I understand b* = -8.0 is quite bluish, but -.6 is not, and that is the result using the uv cut instrument.  So can we assume the base "whiteness" of the paper before adding OBAs is reasonably neutral?  Or another way of looking at it, some years later after the OBAs have lost their uv excitation capability will the paper appear neutral instead of yellowish?

Richard Southworth

Hard to say. OBAs themselves can become yellowish with age. So you might see the paper white's b* shift slightly into positive territory after many years and exposure to daylight.



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Mark D Segal

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Re: Why OBAs in this paper?
« Reply #4 on: March 11, 2018, 12:31:29 pm »

I understand b* = -8.0 is quite bluish, but -.6 is not, and that is the result using the uv cut instrument.  So can we assume the base "whiteness" of the paper before adding OBAs is reasonably neutral?  Or another way of looking at it, some years later after the OBAs have lost their uv excitation capability will the paper appear neutral instead of yellowish?

Richard Southworth

No - not to my thinking anyhow. a*-0.6 is quite neutral, but it's the whole reading that matters, not just one component. I don't think you can assume the paper will look neutral once the OBA fades, nor does one know anything about the time path of fading or whether it fades evenly - maybe Aardenburg has some data on this you could check?
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Mark D Segal (formerly MarkDS)
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rasworth

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Re: Why OBAs in this paper?
« Reply #5 on: March 11, 2018, 12:54:17 pm »

I guess I was assuming most photos would be mounted with low uv exposure.  If true, then the fade curve wouldn't matter much, as long as aging caused a loss of emissivity without an actual OBA reflected color change.  However if the OBA component actually yellows then all bets are off.  I checked earlier on Aardenburg, didn't come up with anything.

Richard Southworth
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digitaldog

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Re: Why OBAs in this paper?
« Reply #6 on: March 11, 2018, 12:54:54 pm »

I understand b* = -8.0 is quite bluish, but -.6 is not, and that is the result using the uv cut instrument. 
It isn't but then if you use UV Cut, the instrument is blind to the reality of the paper itself.


http://digitaldog.net/files/24TroubleWithFWAs.pdf


Placing a UV-blocking filter over the spectrophotometer is a partial solution, but can be an ineffective fix. UV-blocking filters can block all but the visible light spectrum, but you get the best color matches when the print-viewing conditions have the same amount of UV as the light source in the spectrophotometer that’s used to build the paper profile. Filtering UV is like correcting one error by introducing another.
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rasworth

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Re: Why OBAs in this paper?
« Reply #7 on: March 11, 2018, 01:03:41 pm »

My viewing environment is LED throughout the house, so uv cut seems to match up well.  I understand the exposure when viewing in other environments that might not be so uv minimal.

Richard Southworth
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Doug Gray

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Re: Why OBAs in this paper?
« Reply #8 on: March 11, 2018, 01:38:13 pm »

My viewing environment is LED throughout the house, so uv cut seems to match up well.  I understand the exposure when viewing in other environments that might not be so uv minimal.

Richard Southworth

For LED lighting, uV cut (M2) is the best choice. There is virtually no uV in most LED lights. In fact, ColorMunki and iSis, both use a white LED for the M2 measurements. Since there is so little uV, neither needs a uV cut filter.
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rasworth

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Re: Why OBAs in this paper?
« Reply #9 on: March 11, 2018, 02:04:10 pm »

My original question, why did the manufacturer add OBAs to a paper that is apparently close to neutral, is probably not answerable.  A more reasonable question is given the results of the uv cut based profile, l*a*b* = 94.1,-.8,-.6, is this a reasonable paper to use in a low uv environment, and expect to have stable image on a near neutral surface for some number of years.  The closest match in Aardenburg for my printer, an Epson 3880, is Epson Ultra Premim Photo Paper Glossy, which seems to be holding up ok (listed as high in OBAs).  I understand that Epson may well use a different formulation than Red River.

The paper, Red River UltraPro Luster 300, is slightly heavier than some of its competition, and the large sheets handle well without kinking.  Initial test printing with the aforementioned profile is positive.  Given that it will be displayed in low UV environments the changing uv induced emissivity should not be an issue.  There is the possibility the OBA compounds themselves will yellow, I'm willing to live with that exposure given that I haven't seen much of this phenomena with modern papers.

Richard Southworth


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digitaldog

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Re: Why OBAs in this paper?
« Reply #10 on: March 11, 2018, 02:32:20 pm »

My original question, why did the manufacturer add OBAs to a paper that is apparently close to neutral, is probably not answerable.
Mark answered didn't he? It is only 'neutral' in those Lab values if you accept what isn't being measured.

Quote
A more reasonable question is given the results of the uv cut based profile, l*a*b* = 94.1,-.8,-.6, is this a reasonable paper to use in a low uv environment, and expect to have stable image on a near neutral surface for some number of years.

No due to instability of OBAs. Best to avoid them if this is a concern.
Quote
There is the possibility the OBA compounds themselves will yellow, I'm willing to live with that exposure given that I haven't seen much of this phenomena with modern papers.
Wait  ;D
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rasworth

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Re: Why OBAs in this paper?
« Reply #11 on: March 11, 2018, 03:20:52 pm »

Andrew,
I'm assuming "what isn't being measured" are the visible blues generated by the uv excitation.  I don't see an inconsistency with combining a uv cut m2 profile with a viewing environment with little or no uv present, and therefore labeling the paper as near neutral without OBA action.

Richard Southworth
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Ernst Dinkla

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Re: Why OBAs in this paper?
« Reply #12 on: March 11, 2018, 03:42:11 pm »

I would not assume that the paper base without OBA is neutral. Usually it is warm, add enough OBA and it becomes cool. Less expensive than starting from a neutral base paper. That the profile shows a near neutral white point is not just the result of a UV cut Spectrometer, it includes the software extrapolation to say 380nm based on the measurements above 400/420nm. There are often some arbritrary things done in that spectral range. Numbers just copied downwards happens too.

Enough Aardenburg-Imaging results that show shifting to neutral in time of OBA content papers is not always the case. Either the base was never neutral and/or the OBAs degraded to a stain.

http://forum.luminous-landscape.com/index.php?topic=53690.20

Ernst, op de lei getypt.
« Last Edit: March 11, 2018, 03:59:11 pm by Ernst Dinkla »
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digitaldog

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Re: Why OBAs in this paper?
« Reply #13 on: March 11, 2018, 03:52:04 pm »

Andrew,
I'm assuming "what isn't being measured" are the visible blues generated by the uv excitation.
What isn't being measured is what's cut, so yes. It's there. We may see it and maybe differently than the Spectrophotometer and based on the illuminants (there is the one in the Spectrophotometer and one we use to view the prints and they often differ).
Make a profile each way. Examine the soft proof using an Absolute Colorimetric intent and you'll usually see quite a large visual difference between the two profiles. But as I pointed out earlier, there are no rules. If you have a Spectrophotometer that can measure both ways, do so and build two profiles and see which you prefer under your own lighting. But don't assume that because you have a Bstar value that isn't large in the negative direction if you will, that there are no OBAs when the measurement is made to cut them out!
The big issue I see with OBAs is that the print can change over time due to them and I suspect that's not desirable for many.
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rasworth

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Re: Why OBAs in this paper?
« Reply #14 on: March 11, 2018, 04:17:41 pm »

I'm not assuming there are no OBAs, rather that the effect of the OBAs is minimized.  So yes, the OBAs are still there, but if they are not emitting do they have any other effect?  We need a paper chemistry type to answer that one.

It's easy to state we should avoid OBAs, and I use papers that don't contain any. However some people prefer the brighter whites, and the resin coated papers are usually cheaper.  I have profiled several papers with OBAs with an uv cut i1Pro, and they generally end up b*=-2 or "more", i.e. once the OBA is negated the resulting white point tends to yellow.  This paper struck me as unusual because the m2 results ended up close to neutral, and in a uv free viewing environment the whites are still "whiter" than the OBA free papers.

Richard Southworth
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digitaldog

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Re: Why OBAs in this paper?
« Reply #15 on: March 11, 2018, 04:21:55 pm »

I'm not assuming there are no OBAs, rather that the effect of the OBAs is minimized. 
The bit about assuming (sorry) is simply based upon what you read via Lab values from a UV cut reading. And yes, it is easy to state you should avoid OBAs, even detecting them can be tricky although a good ol' black light works well. Bigger point is, if you can measure with UV cut and UV included, do it and build two profiles, then test. Thankfully it's affordable to do so these days. Back in the day, a Spectrophotometer that could read both was expensive and slow (I'm thinking of my old Spectrolino). Noisy too!
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rasworth

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Re: Why OBAs in this paper?
« Reply #16 on: March 11, 2018, 04:31:19 pm »

Let me make sure I understand how an uv cut i1Pro operates - I "assume" the uv from the lamp is eliminated/attenuated, and therefore the reflection to the spectro would contain little or no content from the OBAs.  Am I on track?

Richard Southworth
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digitaldog

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Re: Why OBAs in this paper?
« Reply #17 on: March 11, 2018, 05:03:41 pm »

Let me make sure I understand how an uv cut i1Pro operates - I "assume" the uv from the lamp is eliminated/attenuated, and therefore the reflection to the spectro would contain little or no content from the OBAs.  Am I on track?
There's either a filter or no filter but let's just look at the results, not what is happening deep in the instrument.

I have Lab values from my iSis using M0 and M2 and I'm measuring Epson's Prem Luster paper which has OBAs. M0 the bstar reads -6.72. M2 it measures 2.5. One tells us something about the OBA's while the other isn't really true because again, it isn't measuring without the UV Cut filter. That is why I wrote: if you use UV Cut, the instrument is blind to the reality of the paper itself.


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Mark D Segal

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Re: Why OBAs in this paper?
« Reply #18 on: March 11, 2018, 05:22:31 pm »

There's either a filter or no filter but let's just look at the results, not what is happening deep in the instrument.

I have Lab values from my iSis using M0 and M2 and I'm measuring Epson's Prem Luster paper which has OBAs. M0 the bstar reads -6.72. M2 it measures 2.5. One tells us something about the OBA's while the other isn't really true because again, it isn't measuring without the UV Cut filter. That is why I wrote: if you use UV Cut, the instrument is blind to the reality of the paper itself.

Whoops - this is getting a bit difficult, as double-negatives can be - maybe just at my age. Does your iSis work like the i1Pro2 using a dual scan mode to create the M2 condition? More generally how do you create the M2 data file? With M0 you get the kind of bluish reading we expect from Epson PLPP. Turning to the M2 reading, you say you don't trust it because "it isn't measuring without a UV cut filter." What does this mean - that it is measuring with a UV cut filter? Or measuring with a light source that doesn't excite the FBA? If so, I would expect something like the 2.5 because that M2 measurement is supposed to be neutralizing the OBA impact by not seeing or suppressing the UV - somehow. It's the "somehow" that I would emphasize here - seems that the 2.5 is an approximation, because the filtering may not be accurate. But give or take a bit, we should still expect an M2 b*reading considerably warmer than -6.7 if it's counteraction of the UV is "in the ballpark" - right? If so, the M2 reading may be closer to eventual paper white (after OBA fading) than is the M0 reading, but we don't know how close. Am I making sense here?
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Doug Gray

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Re: Why OBAs in this paper?
« Reply #19 on: March 11, 2018, 05:33:32 pm »

There's either a filter or no filter but let's just look at the results, not what is happening deep in the instrument.

I have Lab values from my iSis using M0 and M2 and I'm measuring Epson's Prem Luster paper which has OBAs. M0 the bstar reads -6.72. M2 it measures 2.5. One tells us something about the OBA's while the other isn't really true because again, it isn't measuring without the UV Cut filter. That is why I wrote: if you use UV Cut, the instrument is blind to the reality of the paper itself.

The basic problem with OBA laden papers is that it will look different depending on the uV content of whatever illuminant you choose to display or show the print. Change it and the print can appear different. There are other issues as well such as metameric shift which is especially a problem for cheap LED and fluorescent lighting but one thing at a time.

Whether profiles using M2 are "true" or not depends on whether the illuminant the paper is viewed under has uV or not. If not, it IS true. The problem is determining whether the light you are viewing the print has uV, and if it only has some, which a lot of regular incandescents do, whether M2, M1, or M0 is the closest match to the level of uV from it.

There is a fairly simple say to determine this with OBA papers.

Measure the Lab value of the white patch on your colorchecker card.

Create a patch in Photoshop and it has to be in Photoshop or some other program that allows Abs. Col. printing. Fill the patch with Lab=(Colorchecker white patch). Then print the patch using each of the three M0, M1, and M2 profiles made for the paper using Absolute Colorimetric. It's easy to print these on the same sheet by positioning them differently across the paper's top and making 3 prints on the same sheet.

Now, cut the patches off so you don't see any surround and have three patches. Good idea to mark the patches with M numbers to keep track.

View these patches against the Colorchecker under the illuminant of interest (home lighting, display lighting, outdoor lighting, etc).

Then just use the Mn Profile that most closely matches.
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