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

[Robert Ardill]

In simple terms, the introduction of OBA’s may produce color issues when one measures the paper to build a printer profile. Does the instrument record this UV or does the instrument filter (cut/exclude) the UV? The discontinued GretagMacbeth Spectrolino had provisions to measure with, or without a UV filter that could be attached to the measurement head. The X-Rite iSis has the ability to measure UV or remove that component from the measured data thanks to the use of a dual illuminant inside the unit. Both devices are expensive. For those in the market for an affordable Spectrophotometer the choice was limited to either a UV Cut or Non-Cut product if there was even an option.
http://www.luminous-landscape.com/reviews/accessories/eye_one_pro_ii.shtml

It's even easier to understand than color gamut!

I don't find it easy to understand Andrew.  I have an i1Pro2 so I can do OBA compensation using i1Profiler (or more quickly using Argyll as it doesn't require a dual-pass scan), but it's not clear to me if I should use OBA compensation and for what conditions. 

That's why I tried to give a scenario in my post above.  Do you agree with what I've said, or do you think I've got it wrong?  If I have it wrong then I really would appreciate it if you would set me straight.

Robert

[GWGill]

You or someone will have to at some point no? How on earth would you know if the compensation worked or not if you didn’t?

Sure, but you don't have to actually be there when you make the profile - someone can measure and send the data, and evaluate the result, independently of where or who makes the profile.

[digitaldog]

I don't find it easy to understand Andrew.  I have an i1Pro2 so I can do OBA compensation using i1Profiler (or more quickly using Argyll as it doesn't require a dual-pass scan), but it's not clear to me if I should use OBA compensation and for what conditions. 

First things first; depends on the conditions. The paper, the illuminates, the software and hardware used to build a profile. You might need the compensation, you might not. Place the print in the condition and look at it.

[GWGill]

So from that what I'm to understand in this discussion is that there needs to be a way to create tweaks during the measuring and creation of a paper profile to correct for the constantly changing color of paper white with various levels of OBA's revealed under different illuminants (as shown in that Minolta link image) and the way to do that is to get the profile to make the rest of the non-paper printed color tones match the bluish look of that paper?

Calling it "tweaks" is one way of putting it - but that's describing a mechanism, not what you are trying to achieve.

What you are trying to achieve is far simpler :- to make the measurements reflect the color appearance under the intended viewing conditions. What needs to be adjusted for is the difference between the illuminant the instrument is using and the viewing illuminant.

I'm assuming this process of OBA compensation also allows targeting the measurement and tweaks within the profile for a specific illuminant/paper OBA behavior.

That's the only way it can work.

To ask it simply is this a question of generating a paper profile to put more yellow in the print or less yellow to get the overall look of the print to match a bluish white paper viewed under a light that will make the paper appear bluish?

The aim is to make the measurements reflect the appearance under the viewing illuminant, so that the color profile can do its job.

Who views prints in daylight?

People with windows ?

It is considered normal enough that graphic arts has adopted as the standard - D50!

Most prints are viewed under lights that don't reach that far into the UV spectrum and if they do you'll be dealing with the EPA and your eye doctor.

A lot of people use incandescent or fluorescent lighting - and it triggers the FWA/OBA's. In the future you may be right - LED lighting is very UV poor, but the fact is that paper makers wouldn't add FWA/OBA's to paper if no-one could see it.

[Tim Lookingbill]

Who views prints in daylight?

People with windows ?

It is considered normal enough that graphic arts has adopted as the standard - D50!

Window light includes the blue canopy skylight contaminator that is not part of D50 spectral emission and the only artificial light that is considered closest to D50 is the 4700K Solux halogen which looks very much like a sunbeam coming through my window.

IOW window light is TOO BLUE and is not an ideal light source to base a color rendering standard. I should know I used to make fine art acrylic paintings on canvas having to use window light to work under and it sucks for showing true color rendering. Once the sun beam shown through my window at the right time of day the colors looked correct.

There's two components of white natural light that makes this very confusing to wrap one's head around and that is the actual color of white D50 light AND what the actual spectral reflectance qualities it exhibits on real objects for instance when I've seen a sunbeam make my acrylic yellows and oranges increase in saturation and luminance on canvas and bluish diffused window light make the yellow and orange shift to cyan and become less saturated and luminous. Which one of those light's components (their color? or spectral reflectance?) created that appearance?

But Andrews point made it more clear for me on what this topic is about...

In simple terms, the introduction of OBA’s may produce color issues when one measures the paper to build a printer profile. Does the instrument record this UV or does the instrument filter (cut/exclude) the UV? The discontinued GretagMacbeth Spectrolino had provisions to measure with, or without a UV filter that could be attached to the measurement head. The X-Rite iSis has the ability to measure UV or remove that component from the measured data thanks to the use of a dual illuminant inside the unit.

[GWGill]

Window light includes the blue canopy skylight contaminator that is not part of D50 spectral emission and the only artificial light that is considered closest to D50 is the 4700K Solux halogen which looks very much like a sunbeam coming through my window.

Daylight is very variable, but I've certainly measured daylight that is pretty similar to D50 during a large number hours around mid-day. But this is off topic - the topic at hand is UV content of illuminants, not their white point or other spectral composition. The nature of a reflective medium is that it's white point automatically changes with the illuminant (times it's reflectance spectrum, which is constant and ideally is close to flat). What doesn't track is a change in relative UV content when the medium has FWA/OBA.

There's two components of white natural light that makes this very confusing to wrap one's head around and that is the actual color of white D50 light AND what the actual spectral reflectance qualities it exhibits on real objects for instance when I've seen a sunbeam make my acrylic yellows and oranges increase in saturation and luminance on canvas and bluish diffused window light make the yellow and orange shift to cyan and become less saturated and luminous. Which one of those light's components (their color? or spectral reflectance?) created that appearance?

The spectrum causes the color. The light you see is the illuminant spectrum times the pigment reflectance spectrum then integrated into the 3 color signals in your eyes. You may well be observing viewing condition effects as well, if there is a drastic change in illumination.

[Stefan Ohlsson]

Daylight is very variable, but I've certainly measured daylight that is pretty similar to D50 during a large number hours around mid-day. But this is off topic - the topic at hand is UV content of illuminants, not their white point or other spectral composition. The nature of a reflective medium is that it's white point automatically changes with the illuminant (times it's reflectance spectrum, which is constant and ideally is close to flat). What doesn't track is a change in relative UV content when the medium has FWA/OBA.The spectrum causes the color. The light you see is the illuminant spectrum times the pigment reflectance spectrum then integrated into the 3 color signals in your eyes. You may well be observing viewing condition effects as well, if there is a drastic change in illumination.

How far into the UV part do you have to measure to be sure to get all the UV light that affects OBA? I sometimes do a special profile for an important exhibition, where I take my time to go the exhibition area to actually measure the light that will be used. I use an ordinary i1Pro2 to measure the light, but I don't know if it can measure all the important parts of the UV spectrum. And if I then use that measurement in i1Profiler and then do a dual scan, does that give me a profile that's corrected for the UV light?

Best

Stefan
www.profiler.nu

[Robert Ardill]

First things first; depends on the conditions. The paper, the illuminates, the software and hardware used to build a profile. You might need the compensation, you might not. Place the print in the condition and look at it.

Yes, I do agree that the acid test is to view the print without OBA compensation under the target illuminant - then if it doesn't look right try it with OBA compensation.  The problem with that, though, is that one print might look fine whereas another might not.  For an exhibition or gallery it wouldn't be feasible to check each print then reprint the ones that don't look right, and mostly we cannot check the print in a customer's house or office.

It would seem to me that it would be sensible to use OBA compensation where we can measure the target illuminant (as, for example, in a gallery).  Equally, if our customer can tell us that they are using D65 fluorescent lighting, say, then, again, using OBA compensation would more that likely improve the print.

So, to generalise, I think that OBA compensation should be used where we know, or can measure, the target illuminant (which is required for OBA compensation anyway).

Of course, the best thing is to use papers that don't have OBAs! (which is my approach .

Robert

[Mark D Segal]

...........Of course, the best thing is to use papers that don't have OBAs! (which is my approach .
Robert

Uhuh, seems like safe advice, but is this a binary matter? Does it make a difference to how you would approach profiling whether the paper has a "little bit" of OBA versus "a lot", or whether the OBA is embedded in the base or in the coating, and exactly what chemical compound it is made of? Maybe there are papers for which the OBA component just isn't worth fussing over, while for others the fuss may indeed be worthwhile?

[Bart_van_der_Wolf]

Uhuh, seems like safe advice, but is this a binary matter? Does it make a difference to how you would approach profiling whether the paper has a "little bit" of OBA versus "a lot", or whether the OBA is embedded in the base or in the coating, and exactly what chemical compound it is made of? Maybe there are papers for which the OBA component just isn't worth fussing over, while for others the fuss may indeed be worthwhile?

I agree with Mark. More important than the amount of UV, is the response of the particular OBA(s) used.

Besides, most silicon based sensors are not all that sensitive to UV wavelengths, so it could only approximate the effect on OBAs that are stimulated by 350-400 nm UV. Is that also the UV wavelength range that these OBAs are stimulated (excited) by, and which longer OBA wavelengths are then emitted as fluorescence?

Cheers,
Bart

[Robert Ardill]

I agree with Mark. More important than the amount of UV, is the response of the particular OBA(s) used.

Besides, most silicon based sensors are not all that sensitive to UV wavelengths, so it could only approximate the effect on OBAs that are stimulated by 350-400 nm UV. Is that also the UV wavelength range that these OBAs are stimulated (excited) by, and which longer OBA wavelengths are then emitted as fluorescence?

Cheers,
Bart

Yes, I agree with Mark too.

The problem, as I see it, is that the OBA causes light to be reflected at a different wavelength: so white becomes blue-ish.  That's fine for making the paper look white, but when we then put ink down over the paper, what happens?  For example, does yellow get a green tint (because the underlying white paper reflects a blue-ish light)? If it does, and the instrument is not UV-cut, then presumably the profile will compensate for this automatically ... without any need for OBA-compensation.

So what is the need for OBA-compensation then?  Presumably, what it will do is to try to make the paper white more yellow ... and in so doing defeat the purpose of putting OBA into the paper in the first place.

With this kind of thinking, it would seem that OBA compensation is really only useful for proofing, so that we can view both the proof and the target side-by-side without the proof looking much whiter than the target (or vice-versa).

I seem to be swinging from one side to the other at this stage .  To OBA-compensate or not to OBA-compensate, that is the question.

Robert

[digitaldog]

So what is the need for OBA-compensation then? 

The simple answer to all this is avoid papers with lots of OBAs! There is no prefect solution and depending on where the prints are viewed, the print may look acceptable or not (one would expect the eye to adapt too).
The basic question is, do you measure with UV or make it go away via filters then, do you compensate for a specific ambient condition? We have tools to measure the light under which a print is examined and use that inside the profile. We have tools (tweaks) for the OBAs. If you can target the profile for where and how the print is viewed, great. If not, all bets are off (if the prints are to be moved about).
What we need is a simple to use and effective profile editor. Something like Kodak's Custom Color ICC which worked inside Photoshop. Something that works like an image editor, not a profile editor (ProfileMaker Pro's module comes to mind as one that seems designed to confuse the end user).

[JRSmit]

Indeed the oba effect varies with the lightsource, i used differents sources, ordinary halogen, led, solux4700, direct sunlight, daylight in a cloudy day, daylight bluesky, behind a window etc. The visual match with the control card simply gives different results (different values for each of the four wegdes).
So what i do is in OBC  to set values , create a profile in m1 condition, evaluate its tone curve in absolute colorimetric setting using docbees profilemanager . Based on my experience i get with this approach the tone curve in ballpark kind of shape in rather quick steps. Then print and visually evaluate the print or prints in the typical lighting situations in house and fine-tune if needed.

Actually, if the amount of oba is not large, creating a profile in m0 condition may be enough.

Anyhow it is a subjectively determined acceptable "point" in a very broad spectrum, so it is just that, nothing more.

[Robert Ardill]

The simple answer to all this is avoid papers with lots of OBAs!

Yes, totally. Canson Baryta is a nice example, with little OBAs; Canson Platine even nicer IMO (with no OBAs).

What we need is a simple to use and effective profile editor. Something like Kodak's Custom Color ICC which worked inside Photoshop. Something that works like an image editor, not a profile editor (ProfileMaker Pro's module comes to mind as one that seems designed to confuse the end user).

How would you use the profile editor?  With something like the XRite control card? Tweak so that the colors match?  I would expect that this sort of approach could lead to some disastrous effects!

Robert

[digitaldog]

How would you use the profile editor? 

http://www.kodak.com/TW/en/professional/products/software/colorFlow/customColor/customColor.shtml

[Robert Ardill]

http://www.kodak.com/TW/en/professional/products/software/colorFlow/customColor/customColor.shtml

Not exactly clear from the link what the workflow would be.  Have you used this tool?  Does it do what you want?  How much does it cost?

Robert

[digitaldog]

Not exactly clear from the link what the workflow would be.  Have you used this tool?  Does it do what you want?  How much does it cost?

Used it for years (since day 1), no longer available. If you know how to edit an image in Photoshop, you know how to edit a profile in Custom Color. Best editor ever, I have a very old Mac setup to run it.

[GWGill]

How far into the UV part do you have to measure to be sure to get all the UV light that affects OBA?

It depends on the particular type of FWA, but typically the peak sensitivity is around 350 nm, and it drops to zero beyond 300nm.

I sometimes do a special profile for an important exhibition, where I take my time to go the exhibition area to actually measure the light that will be used. I use an ordinary i1Pro2 to measure the light, but I don't know if it can measure all the important parts of the UV spectrum.

It can't. It usually stops at 380 nm. You would need a more specialized instrument such as a JETI 1211 UV which goes down to 250nm, or a similarly configured module from Ocean Optics or StellarNet. The normal JETI 1211 goes down to 350nm. But note that ArgyllCMS illumread avoids the need for such instruments, and in fact gives a better result if you make use of the paper you intend to print on.

And if I then use that measurement in i1Profiler and then do a dual scan, does that give me a profile that's corrected for the UV light?

I'm not an i1Profiler expert, but I get the impression that it relies on printing out a series of samples that assume different levels of UV exitation, and then you visually match one of the samples to a reference under the illuminant. This also avoids the need to use a special instrument to measure the illuminant UV levels.

In fact you don't want to measure the UV levels, because you would then have to estimate or measure the FWA spectral excitation curve.

[GWGill]

If it does, and the instrument is not UV-cut, then presumably the profile will compensate for this automatically ... without any need for OBA-compensation.

Well no - that's the point of FWA compensation, it compensates for the fact that the instrument illuminant relative UV level is different from that of the viewing illuminant. If they are the same (i.e. both incandescent), then yes, FWA compensation isn't needed.

[JRSmit]

I would really appreciate it if someone would explain why one would want to use OBA compensation as I find the whole subject very confusing. 

Robert

The measurement instrument, I use I1 Pro2, measures the OBA effect and shows the results, f.i. a grey wedge, with a blue bias depending the amount of OBA. But if one observes the same grey wedge it does not appear so blue as the measurements indicate. This however varies with the sort of lighting/illuminant used.

According to the ISO3664:2009 standard , if you use a illuminant in a light booth that complies with the standard regarding UV light, using the M1 condition during profile creation should result in a correlation between measured and observed wrt the OBA effects.
The M0 condition does also measure OBA effect but so-called undefined, in effect the OBA effect measured is less pronounced than in condition M1.

Even M2, UV-cut, only means that in the measurement the OBA effect is eliminated, but it is not eliminated for the observer.


But in a different illuminant, say a normal household halogen, or a LED light, or a fluorescence energy saving or a mixture of those with daylight without direct sunlight, or direct sunlight, or through a thick window-pane, etc,  the OBA effect varies. Unlike non OBA papers, the spectral behavior of the reflection changes, that is what makes it a moving target.
So ideally if there is only one light condition used for observing, with a known behavior (f.i. compliant with ISO3664:2009 standard), one can create a matching (sort of) profile.

Great for the graphic industry, but what about the individual observer? Then just M0, M1, M2 does not work out of the box, you have to have some way of applying a compensation though trial and error to come to an acceptable result.