Paper | 390 nm Reflectance |
Hahnemuhle Baryta FB | 1% |
Epson Exhibition Fiber Paper | 5% |
Innova Fibaprint Ultra Smooth Gloss | 6% |
Kirkland Pro Glossy Inkjet Photo Paper | 8% |
Hahnemuhle Fineart Baryta | 15% |
Hahnemuhle Fineart Pearl | 27% |
Harman Gloss FB AL | 43% |
Harman Warmtone Gloss FB AL | 58% |
Ilford Gold Fiber Silk Paper | 72% |
Innova Fibaprint Warm Tone Gloss | 78% |
Museo Silver Rag | 85%* |
Hahnemuhle Photo Rag Pearl | 88%* |
Hahnemuhle Photo Rag Baryta | 90%* |
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 (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 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.
Thanks Alan,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 (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.
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?
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
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. [...]
[...]
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.
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?
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