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

[Mark D Segal]

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.

Well Tim, I have. I've had prints hanging on the fridge door from photos of our grandchildren taken at different ages as they progressed, in those days printed on Epson Enhanced Mstte (or whatever they are naming the stuff now - I'd never go back to it with today's paper choices). The OBA fades visibly within a couple of years - the older ones looked more yellow than the newer ones placed beside them, because as the OBA fades, more of the true paper colour shows through. The fading was quite even and did not seem to distort non-white colour, so it never really bothered me all that much, but nonetheless the change at least to the white was undeniable.

[Tim Lookingbill]

Well Tim, I have. I've had prints hanging on the fridge door from photos of our grandchildren taken at different ages as they progressed, in those days printed on Epson Enhanced Mstte (or whatever they are naming the stuff now - I'd never go back to it with today's paper choices). The OBA fades visibly within a couple of years - the older ones looked more yellow than the newer ones placed beside them, because as the OBA fades, more of the true paper colour shows through. The fading was quite even and did not seem to distort non-white colour, so it never really bothered me all that much, but nonetheless the change at least to the white was undeniable.

Thanks for the heads up on Epson Enhanced Matte, Mark.

I have prints on Epson Prem Presentation Matte and haven't experienced fading and yellowing in the past 5 years but then I only use it for testing color gamut shifting and keep them covered among a stack of other papers.

I'ld still like to know if there are non-OBA papers that look just as bright white as Epson Ultra Prem Glossy. I don't have a whole collection of papers to compare, just Epson paper I buy at OfficeMax or Target.

I've got colored Canson Fine Art Paper for pastel drawing I keep in my walk-in closet in a flat file satchel and I'm sure they're OBA/acid free since they look the same as they did 30 years ago when I bought them at Herwecks art supply store in Houston, TX.

[Mark D Segal]

Premium Presentation Matte is the new name for Enhanced Matte. AFAIK, same paper. There are Baryta luster papers available from several manufactures that are either OBA free or have very little.

[Alan Goldhammer]

I'ld still like to know if there are non-OBA papers that look just as bright white as Epson Ultra Prem Glossy. I don't have a whole collection of papers to compare, just Epson paper I buy at OfficeMax or Target.

Tim, it's difficult to get a bright white paper in the absence of some type of chemical additive whether it's baryta, titanium dioxide (seldom used in paper making) or an OBA additive.  OBAs are the cheapest way to go and that's commonly used in inexpensive Xerox paper.  They also use the cheapest fluorescence agents in these uses and it doesn't matter if the paper turns yellow in a year or so as it is usually disposed of before then.  I don't know the Epson paper that you mention so I cannot give you a decent answer.  The two non-OBA papers that I have printed on are Museo Silver Rag and Canson Plantine Rag.  Both are warm papers.  I honestly don't think you can get a true bright white paper that doesn't have some type of additive.  Baryta is pretty inert and you don't have the same issues as with OBAs.

[Tim Lookingbill]

Tim, it's difficult to get a bright white paper in the absence of some type of chemical additive whether it's baryta, titanium dioxide (seldom used in paper making) or an OBA additive...

Titanium dioxide? That what I'ld add as an OBA going by my experience painting with it in acrylics.

I take it, it's toxic and/or too expensive as a paper additive?

I know it's a very stable and pure form of white and very bright. I can mix it with a pure carbon black and get perfect neutral, no off hues due to sulfur content in either paint.

[Robert Ardill]

Tim, probably a Baryta like the Canson Baryta is as white as you'll get without OBAs (it has a little, but very little).  The Barium Sulphate whitens the paper to some extent, as you know.

I started to do some experimentation but to be honest I have my doubts as to whether it's worth the effort.  Here is a start:



(right-click to view full size)

All the SPDs are measured using an i1Pro2 and Argyll spotread.

The top image is the measurement of the paper white - as you can see, there is a lot of OBA in this paper.

The next two images are the SPD of a Solus 4700K and the SPD of the reflection off the paper illuminated by this lamp.  Even though the Solux has very little UV (allegedly) it does seem that it has some as there's a hump around 450nm.

The bottom two images are the SPD of a fluorescent D65 tube and below that the SPD of the reflection off the paper illuminated by this lamp.  If the spikes are ignored you can see that the readings below 500nm are significantly higher in the reflected SPD, showing the effect of the UV on the paper OBA.

The fact is that a print viewed under the Solux will look very different to it viewed under the fluorescent, naturally, OBAs and UV notwithstanding.

So the test would have to be under the same illuminant, and it would seem to me that the Solux is the better choice as it has a very smooth SPD.

So:
- profile the paper with and without OBC.
- print spot colors with the two profiles
- illumine both prints with the Solux and measure the reflected Lab color of each spot.  If the OBC is working correctly then the Lab values of the OBC test print should be closer to the image Lab values.

Does that make sense, or is there an easier way (like photograph the two images side by side)?

It does seem like a lot of work!!  Which may explain why not too many people have bothered.

Robert

[Tim Lookingbill]

The fact is that a print viewed under the Solux will look very different to it viewed under the fluorescent, naturally, OBAs and UV notwithstanding.

So the test would have to be under the same illuminant, and it would seem to me that the Solux is the better choice as it has a very smooth SPD.

So:
- profile the paper with and without OBC.
- print spot colors with the two profiles
- illumine both prints with the Solux and measure the reflected Lab color of each spot.  If the OBC is working correctly then the Lab values of the OBC test print should be closer to the image Lab values.

Does that make sense, or is there an easier way (like photograph the two images side by side)?

It does seem like a lot of work!!  Which may explain why not too many people have bothered.

Robert

That's not the test I asked for twice already, Robert, so I don't know why you keep going through the trouble of even responding with your own setup. If it's because you're trying to eliminate any subjectivity by only showing spot colors with one light source (Solux) which the majority of the public at large don't view prints under, then you're setup is not a reflection of real world conditions of how humans view a printed color image on paper with or without OBA's.

We don't photograph in a lab.

We don't view prints in a lab.

And we don't print so we're within specs of spectral plots and spot color Lab numbers. I and most folks I know don't view prints this way so a controlled lab setup is pointless.

[Mark D Segal]

That's not the test I asked for twice already, Robert, so I don't know why you keep going through the trouble of even responding with your own setup. If it's because you're trying to eliminate any subjectivity by only showing spot colors with one light source (Solux) which the majority of the public at large don't view prints under, then you're setup is not a reflection of real world conditions of how humans view a printed color image on paper with or without OBA's.

We don't photograph in a lab.

We don't view prints in a lab.

And we don't print so we're within specs of spectral plots and spot color Lab numbers. I and most folks I know don't view prints this way so a controlled lab setup is pointless.

I think it's easy to get carried away with technical analyses and forget to relate the results to the difference they make to real world outcomes and contexts. That said, if you're trying to understand what's happening under the hood - for whatever it's worth - scientific procedure is the only way to go.

[Tim Lookingbill]

I think it's easy to get carried away with technical analyses and forget to relate the results to the difference they make to real world outcomes and contexts. That said, if you're trying to understand what's happening under the hood - for whatever it's worth - scientific procedure is the only way to go.

I already know what's happening scientifically under the hood, Mark.

I'm trying to see how it manifests in the real world and I'm not seeing it as much an issue in this regard to justify the amount of work and concern involved to fix it.

If I could see one good example that would get me to say..."Oh yeah, we need to go to these lengths to head this off before our client wants their money back because their print looks like crap under their lights and/or the paper white has turned a funky color after a year hanging next to window light."...then I'ld finally get a good idea about the concern and reasons for fixing it.

[Mark D Segal]

I already know what's happening scientifically under the hood, Mark.

..............

You may, but there are others..........

At the same time, I hear you - I too think it's productive to have a practical focus on outcomes that matter.

[Ernst Dinkla]

The common whitening agent for the PE barrier layer at the print side of RC paper is TiO2 in one of its crystal versions, the back side PE barrier is transparent. I suspect at least some Moab natural fine art papers have TiO2 whitening agents; UV absorption but no fluorescence in the visual spectrum. I expect more papers to have TiO2 as part of a mix of whitening agents, less so where OBA content should not have competition in UV absorption, barite is then a better companion. TiO2 is quite common in paper production. I'm not aware of toxicity of TiO2 in this application, in sun creams it is an issue.

Met vriendelijke groet, Ernst

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

[Robert Ardill]

That's not the test I asked for twice already, Robert, so I don't know why you keep going through the trouble of even responding with your own setup. If it's because you're trying to eliminate any subjectivity by only showing spot colors with one light source (Solux) which the majority of the public at large don't view prints under, then you're setup is not a reflection of real world conditions of how humans view a printed color image on paper with or without OBA's.

Well Tim, I have no idea how you would go about doing the test you want (and in particular how I could show this to you over the web).

If you want to see the effect of OBC on a particular paper then you have to print a sample both with and without OBC and see if there's a significant difference.  You can't do OBC without specifying the light source, so whether that light source is a Solux 4700K, cheapo fluorescent, or whatever, makes no difference, as long as you specify which it is.

Doing a comparison between a paper that has OBA and one that doesn't isn't going to be of much use because the paper characteristics and the profiles will be different ... so of course you will get a variation.

At any rate, I have done a test with a spectrum that I have posterized.  Under the Solux 4700K I can see no difference between the OBC print and the non-OBC print.

So I then tried to produce an OBC profile for a fluorescent (from the saved scan data) as this may have more UV ... but i1Profiler screws up the profile completely.  Producing a non-OBC profile from the saved scan data works fine ... so there's definitely a major bug here.  I'll report it to XRite.

The alternative would be to use Argyll ... but I've run out of time.

Anyway, Tim, why don't you spell out the steps you want in your test ... and then why don't you do it yourself?  I would be very interested to see what you come up with.

Robert

[Alan Goldhammer]

TiO2 is quite common in paper production. I'm not aware of toxicity of TiO2 in this application, in sun creams it is an issue.

It's commonly used in sunscreens and has some other cosmetic applications as well so toxicity is not an issue.

[Ernst Dinkla]

It's commonly used in sunscreens and has some other cosmetic applications as well so toxicity is not an issue.

In sun screens the TiO2 particles are covered with silicate for a reason.

Met vriendelijke groet, Ernst

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
December 2014 update, 700+ inkjet media white spectral plots

[Robert Ardill]

Well, I've done a test using Argyll.  I've produced 3 profiles for the high-OBA Permajet Oyster paper:
- Standard D50 illuminant
- Fluorescent D65 illuminant
- Fluorescent D65 illuminant with OBC

Here is a photograph of the 3 test strips, photographed under the D65 fluorescent:



(right-click to view full size).

I've blurred the image slightly to remove any local variations due to noise etc.

You can get the tif image here: http://www.irelandupclose.com/customer/LL/FWA-Test-Image.tif

There is a lightness and hue shift between the strips.  The D50 colors are lighter and generally have more magenta and yellow than the D65-illuminant image.  This is also true between the D50 and D65-OBC image, but the differences are slightly greater.  This is a bit puzzling as I would have expected the OBC-compensated image to have more yellow (since the OBA should be giving a blue-white tint and to compensate for this the OBC should add yellow ... to my mind, that is).  I'll ask Graham Gill for his view on this.

So, based on this and with the Argyll profile, I would say that the differences are subtle and more pronounced on some colors than others.  Using and illuminant-compensated profile certainly seems to produce better results than using a standard D50-illuminant profile.  There are further slight improvements with OBC.  With Argyll there is no additional effort in producing the OBC profile over the illuminant-compensated profile, so why not do it?  Of course the target illuminant needs to be known.

Between D50 and D65 there isn't a huge difference, but if the target illuminant was a warm incandescent then the differences would probably be more significant.

Anyway ... I hope that's of interest and gives some food for thought.  My general feeling is that for most images using a standard D50 profile is fine as it will cover a good range of illuminants.  FWA compensation is probably only worth doing for specific images that just don't look right under the target illuminant.

Robert

[Tim Lookingbill]

Well, I've done a test using Argyll.  I've produced 3 profiles for the high-OBA Permajet Oyster paper:
- Standard D50 illuminant
- Fluorescent D65 illuminant
- Fluorescent D65 illuminant with OBC

Here is a photograph of the 3 test strips, photographed under the D65 fluorescent:



(right-click to view full size).

I've blurred the image slightly to remove any local variations due to noise etc.

You can get the tif image here: http://www.irelandupclose.com/customer/LL/FWA-Test-Image.tif

There is a lightness and hue shift between the strips.  The D50 colors are lighter and generally have more magenta and yellow than the D65-illuminant image.  This is also true between the D50 and D65-OBC image, but the differences are slightly greater.  This is a bit puzzling as I would have expected the OBC-compensated image to have more yellow (since the OBA should be giving a blue-white tint and to compensate for this the OBC should add yellow ... to my mind, that is).  I'll ask Graham Gill for his view on this.

So, based on this and with the Argyll profile, I would say that the differences are subtle and more pronounced on some colors than others.  Using and illuminant-compensated profile certainly seems to produce better results than using a standard D50-illuminant profile.  There are further slight improvements with OBC.  With Argyll there is no additional effort in producing the OBC profile over the illuminant-compensated profile, so why not do it?  Of course the target illuminant needs to be known.

Between D50 and D65 there isn't a huge difference, but if the target illuminant was a warm incandescent then the differences would probably be more significant.

Anyway ... I hope that's of interest and gives some food for thought.  My general feeling is that for most images using a standard D50 profile is fine as it will cover a good range of illuminants.  FWA compensation is probably only worth doing for specific images that just don't look right under the target illuminant.

Robert

That test strip image doesn't tell me how a color photograph of a real scene with a wide range of colors will look on white paper whether it has OBA's or not. I can't see any of the effects from light or OBA in that strip.

You can talk six ways to Sunday about this and still not communicate the real importance of mitigating against these optical issues unless you show it in a real world situation.

[Robert Ardill]

That test strip image doesn't tell me how a color photograph of a real scene with a wide range of colors will look on white paper whether it has OBA's or not. I can't see any of the effects from light or OBA in that strip.

You can talk six ways to Sunday about this and still not communicate the real importance of mitigating against these optical issues unless you show it in a real world situation.

Well, we'll have to differ there Tim.  In my view you first need to demonstrate whether or not there's a difference under controlled conditions, then when you've understood what is happening (if anything) you can move on to an actual photograph of a scene.

What the photograph of the three strips above shows is that there is only a marginal difference ... with this particular illuminant, and this particular paper, and this particular profile.  Printing a real-world scene would have shown the same, but it would have been much more difficult to see the differences.

What I don't know at the moment is whether the very slight differences on the three strips is due to the OBC not being very effective, or because there's not much UV in the illuminant (quite possibly the reason from what I now understand about the amount of UV in off-the-shelf strip lights).  What I need to do is to try to find out how to estimate the UV in an illuminant, and then pick a typical illuminant that does have quite a lot of UV and repeat the experiment.

What I don't understand is why you don't try the test your way ... at least then we would have two approaches to the problem and perhaps yours would prove move conclusive.

Robert

[Tim Lookingbill]

What I don't understand is why you don't try the test your way ... at least then we would have two approaches to the problem and perhaps yours would prove move conclusive.

Because I don't have access to non-OBA inkjet paper. I'm only using Epson Ultra Prem Glossy with OBA which didn't change the look that much as evident in the photo of the white rose print demo I posted earlier.

If you're suggesting I do the same test with a print of an image with a wide range of colors on the same Epson paper viewed under the same variety of lights as in the photo, that I can do. I do have to wait for overcast light which according to local weather forecast may be tomorrow. I don't want to view under lights where there is a full blue canopy sky from a bright sunny day.

But I was hoping someone would have another brand of OBA paper where it acted on the color differently than the Epson viewing under a variety of lights. It seems so far from folk's responses on this thread their experiences are different from what I depicted in the photo demo suggesting not all OBAs are alike in this regard.

[GWGill]

Well, I've done a test using Argyll.  I've produced 3 profiles for the high-OBA Permajet Oyster paper:
- Standard D50 illuminant
- Fluorescent D65 illuminant
- Fluorescent D65 illuminant with OBC

Here is a photograph of the 3 test strips, photographed under the D65 fluorescent:

Hi Robert,
            I'm not sure what you hoped to show. For a start, the level of UV in a normal fluorescent light is typically quite low - it may even be lower than that you are getting from the Solux (which I am presuming is what you are using for your "D50" ?). Second, if a print is setup for D50, I'm not sure what the point of observing it under the D65 is - it can be quite tricky to figure out what to expect.

[Robert Ardill]

Hi Robert,
            I'm not sure what you hoped to show. For a start, the level of UV in a normal fluorescent light is typically quite low - it may even be lower than that you are getting from the Solux (which I am presuming is what you are using for your "D50" ?). Second, if a print is setup for D50, I'm not sure what the point of observing it under the D65 is - it can be quite tricky to figure out what to expect.

Hi Graeme,

Well, what I'm trying to demonstrate (for myself) is that a print with OBC will look better than a print without OBC under the target illuminant.  So on the test image above, the top strip has OBC for the fluorescent lamp, the middle strip does not, but does have illumination compensation for the same fluorescent lamp.  There is a difference between them, but it is very small - quite possibly because the fluorescent has little UV.

The D50 strip at the bottom is there to attempt to demonstrate what the effect of viewing an image profiled to the standard illuminant compares to images that have illumination compensation and OBA compensation.  The reason for that is that if the differences are significant then it makes more sense to use IC/OBC when profiling a paper.  If the differences are minor/insignificant, then why bother going to the trouble? ... just let chromatic adaptation handle it.

Is there some way, using Argyll, to estimate the level of UV in the illuminant?  Here are plots from illumread for the fluorescent lamp:



Robert