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Author Topic: OBAs & Black light - how reliable a method is it?  (Read 7146 times)

shewhorn

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OBAs & Black light - how reliable a method is it?
« on: August 13, 2010, 02:09:30 pm »

I have some samples of Ilford GFS. I'm about to scan in the target to build a profile and I need to know if it has OBAs or not. Ilford's website is not of much help so I grab the black light. Sitting next to the Ilford paper is a print I made from the previous night using Harman FB AL Warmtone. I wasn't really looking at the Harman paper but it lit up like a Vegas billboard and caught my attention. Strangely enough... this paper from what I understand is NOT supposed to have OBAs and that leads me to wonder if using a black light to check for OBAs is an unreliable method (seems as if there's a few possible outcomes... either it is unreliable, it is reliable and there are OBAs in FL AL Warmtone (not what I would expect) or... somehow a different paper got packaged into an FB AL Warmtone box)?

Cheers, Joe
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cybis

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Re: OBAs & Black light - how reliable a method is it?
« Reply #1 on: August 13, 2010, 03:47:54 pm »

I use a slightly different method to determine if papers contain OBA. Since OBA works by absorbing UV light and reemitting it in the visible spectrum, measuring the spectral response of different papers with a spectrophotometer should tell us if they contain OBA or not. UV light is electromagnetic radiation with a wavelength shorter than that of visible light in the range 10 nm to 400 nm. The shortest wavelength my device can measure is 390 nm. My assumption is that the 390 nm reflectance intensity is approximately inversely proportional to the amount of OBA.

Here are the results from most OBA to the least (or none):

Paper390 nm Reflectance
Hahnemuhle Baryta FB1%
Epson Exhibition Fiber Paper5%
Innova Fibaprint Ultra Smooth Gloss6%
Kirkland Pro Glossy Inkjet Photo Paper8%
Hahnemuhle Fineart Baryta15%
Hahnemuhle Fineart Pearl27%
Harman Gloss FB AL43%
Harman Warmtone Gloss FB AL58%
Ilford Gold Fiber Silk Paper72%
Innova Fibaprint Warm Tone Gloss78%
Museo Silver Rag85%*
Hahnemuhle Photo Rag Pearl88%*
Hahnemuhle Photo Rag Baryta90%*

*Manufacturer claims no OBA
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Alan Goldhammer

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Re: OBAs & Black light - how reliable a method is it?
« Reply #2 on: August 13, 2010, 04:19:18 pm »

I use a slightly different method to determine if papers contain OBA. Since OBA works by absorbing UV light and reemitting it in the visible spectrum, measuring the spectral response of different papers with a spectrophotometer should tell us if they contain OBA or not. UV light is electromagnetic radiation with a wavelength shorter than that of visible light in the range 10 nm to 400 nm. The shortest wavelength my device can measure is 390 nm. My assumption is that the 390 nm reflectance intensity is approximately inversely proportional to the amount of OBA.
Your approach is almost correct.  The OBA(s) (as we really don't know what agent or agents the manufacturer is using), absorbs light at one wavelength and emits light via fluorescence at a second wavelength.  What is happening is at the absorption wavelength you don't get much reflectance as the dye is absorbing light.  It's safe to say that at 390nm this could be a result of the OBA but it won't necessarily be inversely proportional to the amount of OBA; for that you would need to know more details about the exact agent.  There are several websites that have spectral charts of papers and you can see what the presence of OBAs does to the reflectance pattern.  One is at http://www.pusztaiphoto.com/articles/printing/spectrums/webchart.aspx  There was a thread on this several months ago where I and others went into this in more detail.  If you want more information on this send me a PM as I did a fair amount of work in this area during my scientific career.

The other good source is Ernst Dinkla's site at:  http://www.pigment-print.com/spectralplots/spectrumviz_1.htm

Alan
« Last Edit: August 13, 2010, 04:25:29 pm by Alan Goldhammer »
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cybis

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Re: OBAs & Black light - how reliable a method is it?
« Reply #3 on: August 13, 2010, 04:44:39 pm »

Thanks Alan,

The two links you provided look very interesting.

Since we don't know the specific OBA agents used, is there an objective quantitative method for deducting the amount of OBA from the spectral curve? I see what you mean about the 390 nm reflectance alone not being the ideal way to measure OBA (I suppose there could be a UV dip without a blue hump). Is there some way to measure both the UV dip and the blue hump, and then reduce it to one number directly indicative of the amount of OBA?
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Ernst Dinkla

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Re: OBAs & Black light - how reliable a method is it?
« Reply #4 on: August 13, 2010, 05:41:14 pm »

The shortest wavelength my device can measure is 390 nm. My assumption is that the 390 nm reflectance intensity is approximately inversely proportional to the amount of OBA.


TiO2 is a very good whitening agent without fluorescence effects. Yet it does absorb UV light though mainly at shorter UV wavelengths than FBAs do and it emitts the absorbed energy again as heat so beyond the visual spectrum. I'm not sure whether spectrometers that measure up to the 380 Nm are affected by the TiO2 UV absorption but it could spoil your assumption. If there's a dip at that wavelength and a peak near 440Nm then it is very likely an FBA that creates that effect.

With spectrometer readings of paper white expressed in Lab values a negative b value is seen as an indication of an FBA effect. A blue pigment + a lower total white reflectance could create a negative b value as well but the lower reflectance would tell it isn't an FBA effect.


met vriendelijke groeten, Ernst Dinkla

spectral plots of +100 inkjet papers:
http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
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Alan Goldhammer

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Re: OBAs & Black light - how reliable a method is it?
« Reply #5 on: August 13, 2010, 07:53:52 pm »

Thanks Alan,

The two links you provided look very interesting.

Since we don't know the specific OBA agents used, is there an objective quantitative method for deducting the amount of OBA from the spectral curve? I see what you mean about the 390 nm reflectance alone not being the ideal way to measure OBA (I suppose there could be a UV dip without a blue hump). Is there some way to measure both the UV dip and the blue hump, and then reduce it to one number directly indicative of the amount of OBA?

No, I don't think so.  Each compound has it's own spectral properties.  In addition, some papers have OBAs in the coating and others in the paper leading to different effects.  As I noted, I'm not sure that it's really worth the worry compared to other issues relating to color stability.  You might want to go here:  http://www.aardenburg-imaging.com/index.html and look at some of the work that Mark is doing regarding color fading.  It's cheap enough to become a member and you have access to all the test results.  There are some real counter intuitive results so far.  Some OBA papers seem to have better fade resistance than others without OBAs and we really don't know the reason for this yet.

Alan
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shewhorn

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Re: OBAs & Black light - how reliable a method is it?
« Reply #6 on: August 13, 2010, 11:47:02 pm »

Thanks everyone, fascinating information. So it would appear that the Black Light is just a quick reality check. It might give you an idea if something is going on but it would also appear as if there's a lot of figurative grey area. It would appear as if there are some OBAs in the Harman FB AL but perhaps not as much as some other papers. The question then is... at what point do I make the call to use the UV filter?

Cheers, Joe
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Ernst Dinkla

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Re: OBAs & Black light - how reliable a method is it?
« Reply #7 on: August 14, 2010, 05:51:50 am »

Thanks everyone, fascinating information. So it would appear that the Black Light is just a quick reality check. It might give you an idea if something is going on but it would also appear as if there's a lot of figurative grey area. It would appear as if there are some OBAs in the Harman FB AL but perhaps not as much as some other papers. The question then is... at what point do I make the call to use the UV filter?

Cheers, Joe

In measuring targets for profile creation the call for the UV filter is more a case of what the print's illumination will be on display and how it will be framed. Both for FBA or non-FBA papers. If either illumination or framing will not bring UV light to the print then it has little sense to use FBA paper but even with the use of that paper you will use an UV-cut measuring device considering the display conditions.

More extreme for this forum: if the print will be used outdoors with no UV protection then one would use a normal spectrometer and create a profile for 6500 K. Both for FBA and non-FBA media.


met vriendelijke groeten, Ernst Dinkla

Try: http://groups.yahoo.com/group/Wide_Inkjet_Printers/
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nilo

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Re: OBAs & Black light - how reliable a method is it?
« Reply #8 on: August 14, 2010, 10:20:56 pm »

Could you measure the degree of brighteners present in Canson Platin Fibre Rag for me? I have no means of doing that and there is no data about it in the above mentioned sources.

EDIT: I didn't look well enough, into the data produced by Ernst Dinkla in the wonderful SpectrumViz http://www.pigment-print.com/spectralplots/spectrumviz_1.htm It's all there!
« Last Edit: August 14, 2010, 10:39:31 pm by Nino Loss »
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MHMG

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Re: OBAs & Black light - how reliable a method is it?
« Reply #9 on: August 15, 2010, 07:23:01 pm »

Could you measure the degree of brighteners present in Canson Platin Fibre Rag for me? I have no means of doing that and there is no data about it in the above mentioned sources.

Canson Platine Fiber Rag is OBA-free. Whitepoint information about this paper and other new papers will be added to the Aardenburg database within the next month or so.  Platine has a high L* (lightness) value with a* and b* essentially zero when measured for D50 illuminant condition which means under D50 lighting or something similar (5000K sunlight) it will look neutral, appearing neither cool or warm.
BTW, although Canson Platine is OBA free, Canson baryta photographique has a moderate level of OBAs. It will also be added to the database soon.

I really like the texture of both papers very much, but they are very different. As noted by others, Platine definitely has a texture but it is tightly ordered and very pleasing to my eye, and it has a rare quality that even after spraying with a thin coat of acrylic (like HN protective spray or Premier Print Shield) it's final finish is equally appealing if not more so.  Canson Baryta Photographique is my personal choice for the most "traditional air-dried F surface photo paper" appearance of all the "traditional photo" inkjet papers I've seen (and I've seen just about all of them). It's gorgeous, but the moderately high level of OBAs are cause for concern in terms of whitepoint stability over time. But one can not, and I must emphasize this point, cannot accurately assess the impact of the OBAs on whitepoint stability over time without product-specific testing. That testing is now getting underway for these two papers using two popular OEM ink sets, Canon LUCIA and Epson K3VM. I'd love to include HP Vivera pigment as well, but I don't have access to this platform and no AaI&A members have submitted yet.

kind regards,

Mark
http://www.aardenburg-imaging.com
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nilo

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Re: OBAs & Black light - how reliable a method is it?
« Reply #10 on: August 15, 2010, 09:07:18 pm »

Canson Platine Fiber Rag is OBA-free. Whitepoint information about this paper and other new papers will be added to the Aardenburg database within the next month or so. [...]


Thank you Mark, for letting us know! I can't wait to see that data.
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nilo

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Re: OBAs & Black light - how reliable a method is it?
« Reply #11 on: August 18, 2010, 08:28:31 am »

[...]
I really like the texture of both papers very much, but they are very different. As noted by others, Platine definitely has a texture but it is tightly ordered and very pleasing to my eye, and it has a rare quality that even after spraying with a thin coat of acrylic (like HN protective spray or Premier Print Shield) it's final finish is equally appealing if not more so.  Canson Baryta Photographique is my personal choice for the most "traditional air-dried F surface photo paper" appearance of all the "traditional photo" inkjet papers I've seen (and I've seen just about all of them). It's gorgeous, but the moderately high level of OBAs are cause for concern in terms of whitepoint stability over time. But one can not, and I must emphasize this point, cannot accurately assess the impact of the OBAs on whitepoint stability over time without product-specific testing. That testing is now getting underway for these two papers using two popular OEM ink sets, Canon LUCIA and Epson K3VM. I'd love to include HP Vivera pigment as well, but I don't have access to this platform and no AaI&A members have submitted yet.

kind regards,

Mark
http://www.aardenburg-imaging.com

Ernst Dinkla's SpectraViz categorizes papers nicely. CIFA Platine is in the folder "Satin, Luster, Pearl" together with HM PR Baryta and Ilford GFS. To my eyes the surface is maybe a bit rougher than that. With the light from an angle it is a bit glittery. When viewed under average viewing conditions the paper appears more like semi-matte. After my initial euphoria and promising first tests, I have tro contradict myself and admit that I have great trouble getting decent Black and Gamut out of this paper. Anyone???

CIFA Baryta Photographique, in the SpectraViz, classification, is found under "High Gloss, Glazed". It's surface is very fine and semi-gloss like. Like you say, Mark, till now it was very easy to get beautiful prints with a "traditional" look out of this paper. I hope test results will turn out favorable for this paper.

regards
nino
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narikin

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Re: OBAs & Black light - how reliable a method is it?
« Reply #12 on: August 30, 2010, 04:56:24 pm »

Ernst Dinkla's SpectraViz categorizes papers nicely. CIFA Platine is in the folder "Satin, Luster, Pearl" together with HM PR Baryta and Ilford GFS. To my eyes the surface is maybe a bit rougher than that. With the light from an angle it is a bit glittery. When viewed under average viewing conditions the paper appears more like semi-matte. After my initial euphoria and promising first tests, I have tro contradict myself and admit that I have great trouble getting decent Black and Gamut out of this paper. Anyone???

CIFA Baryta Photographique, in the SpectraViz, classification, is found under "High Gloss, Glazed". It's surface is very fine and semi-gloss like. Like you say, Mark, till now it was very easy to get beautiful prints with a "traditional" look out of this paper. I hope test results will turn out favorable for this paper.


Indeed Spectra Viz is extremely useful, (a huge THANKS to Ernst!) and one can draw many conclusions from it:
many of the papers are so similar in their graphs, that they reveal a lot more than they should about who makes what - for example compare the Canson Baryta with Ilford GFS, which track each other more or less identically! Hmmm.

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narikin

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Re: OBAs & Black light - how reliable a method is it?
« Reply #13 on: August 30, 2010, 08:18:46 pm »

dI really like the texture of both papers very much, but they are very different. As noted by others, Platine definitely has a texture but it is tightly ordered and very pleasing to my eye, and it has a rare quality that even after spraying with a thin coat of acrylic (like HN protective spray or Premier Print Shield) it's final finish is equally appealing if not more so.  Canson Baryta Photographique is my personal choice for the most "traditional air-dried F surface photo paper" appearance of all the "traditional photo" inkjet papers I've seen (and I've seen just about all of them). It's gorgeous, but the moderately high level of OBAs are cause for concern in terms of whitepoint stability over time. But one can not, and I must emphasize this point, cannot accurately assess the impact of the OBAs on whitepoint stability over time without product-specific testing. That testing is now getting underway for these two papers using two popular OEM ink sets, Canon LUCIA and Epson K3VM. I'd love to include HP Vivera pigment as well, but I don't have access to this platform and no AaI&A members have submitted yet.
Mark
http://www.aardenburg-imaging.com

thanks for very useful input Mark.

Any word on the Breathing Color papers - like Optica One?  it seems to have medium(?) OBA's, but then that isnt the end of the world, as you say above.  very nice surface

I cant see it in Aardenberg site, or Ernst's list, but maybe am looking in the wrong place?
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MHMG

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Re: OBAs & Black light - how reliable a method is it?
« Reply #14 on: August 30, 2010, 10:29:43 pm »

thanks for very useful input Mark.

Any word on the Breathing Color papers - like Optica One?  it seems to have medium(?) OBA's, but then that isnt the end of the world, as you say above.  very nice surface

I cant see it in Aardenberg site, or Ernst's list, but maybe am looking in the wrong place?

I have one sample of Optica One in test so far. It was printed on an Epson 4880 with Epson K3VM ink and has now reached a total of 80 megalux hours light exposure in test. You can locate this sample in the AaI&A light fade test results database as ID#87 or by filtering the list for [paper/media] [contains] "optica".  I rate this paper based on AaI&A criteria for UV Δb* Influence as having high OBA content, and it is showing the classical OBA burnout in light fade testing. That said, it still retained an 81% I* color value for the media whitepoint color patch at the 50 megalux hour mark, but it is now down to 67% I* color accuracy for the media whitepoint patch as of the 80 megalux hour mark.  Nevertheless, this white point stability result beats most other comparably OBA-loaded papers I've tested to date, so the coating formulation in the Optica paper has pretty good compatibility with Breathing Color's choice of OBA chemistry.
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narikin

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Re: OBAs & Black light - how reliable a method is it?
« Reply #15 on: August 31, 2010, 08:13:30 am »

Mark - many thanks for your hard work and the results are great reference, and can only get more useful as things move forward.

when I simply sort the table results by conservation display rating >40 Megalux (for example), it is amazing how many OBA containing papers are in there doing fine - the majority in fact have some OBA's!

are we somewhat over-reacting to the OBA issue?  I did find your reply (below) on another post most helpful, but was nonetheless surprised how many OBA papers were doing very well in the longer term fade tests, and how many non-OBA papers were not necessarily any 'better', or had indeed failed to even reach this level.  I do get that it is not just OBA's here - but the whole package of ink/coating/paper/OBA's - but the end results show that simply filtering out OBA's is not the right approach to finding a long print life.

One is indeed well served to avoid inkjet papers with high levels of fluorescence (correlates to high OBA content) because as a general rule, these papers wreak havoc with color managed workflows, show obvious whitepoint and highlight color "yellowing" over time, and the very bright-white appearance that endeared the printmaker to use said papers can be killed immediately at the framer's studio if the customer chooses a UV-absorbing glazing (OP3 plexi, museum glass,etc.). Where the "OBA versus no OBA" subject becomes decidedly more ambiguous is when the paper manufacturer uses OBAs to fine tune the whitepoint rather than dominate the whitepoint with fluorescence. In this situation, some "OBA tweaked" papers can exhibit better whitepoint stability performance over time than some OBA-free papers. In other words, the OBA burnout will not have a huge effect on the image appearance and the actual fading of the colorants will dominate. Then it gets down to ink/paper chemistry compatibility such that some OBA-free papers can underperform with certain inks while some OBA-tweaked papers can outperform. Product-specific testing with testing protocols that are designed to accurately identify the OBA fade characteristics in addition to the colorant fade properties, is then required for a more rigorous answer. Without such testing, it can easily become an erroneous decision to reject a paper, say for example Hahnemuhle Photo Rag that contains low levels of OBA in the paper core, on the basis that it might have poorer stability with one's chosen printer and inks than a similar yet OBA-free paper.
Mark
http://www.aardenburg-imaging.com

« Last Edit: August 31, 2010, 09:15:10 am by narikin »
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