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Thread: Optical brighteners OBA FWA

  1. #1
    Member PanozJani is on a distinguished road
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    Optical brighteners OBA FWA

    @ super silja

    http://www.argyllcms.com/doc/instruments.html#i1p

    http://www.argyllcms.com/doc/FWA.html

    Good profiling applications will deal with OBA's. Also I've compared both instruments for monitor calibration. The one without UV cut filter "won".

    Since he wants to provide service with this instrument, he must be a purist IMO.
    best regards
    Last edited by PanozJani; 08-15-2011 at 02:28 AM.

  2. #2
    shampa
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    AFAIK, the UV cut filter only affects the illumination, not the reading so should have no effect on monitor calibration.

    But I agree for print profiling the non-UV cut is superior. Even better is something like an i1sis that can simultaneously measure with/without UV

  3. #3
    aaron125
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    this is what a UV cut device is/does

    Unfortunately you are incorrect in your assumptions regarding how UV cut works. It has absolutely nothing whatsoever to do with the light source.

    example: i1 Pro UV cut spectro
    In an i1-cut, or any other brand UV cut spectro, the UV cutting takes place by means of a filter which removes (cuts) a portion of the spectrum, mostly cutting in the UV range of frequencies. This is performed by a physical filter, a piece of coated glass usually. That is also why UV cut cannot switched on/off in an i1Pro - if it were something in the light source then every UV cut device could also be a non-cut device by changing the light but as explained, UV cut has nothing to do with the illumination.

    It is always a much better idea to measure as much as possible, so do not cut UV, and then if desired, perform UV cutting in software like some apps are currently performing. The problem with UV cut devices is that it is cutting the UV before the UV is able to be measured. So how does one know exactly how much UV is being cut? It isn't disclosed on any device's specification sheet, nor do manufacturers seem to be willing to provide any detail either. Please let me know if I am mistaken, would be very interested to find out exactly which part of the spectrum is being cut & by how much.

    The problem with UV cut devices is also that they don't really seem to work all that well. Because the UV is cut before being detected, this in effect is similar to changing the light source. This is not a good idea because the paper with the OBA included will just about never be viewed or illuminated by any source which has no UV or very little UV in it's spectrum.

    Best solution is also the simplest. Just don't use media with OBA. These type of papers are far too bright, white, blue, etc. to be effective for fine art prints. With the abundance of extremely high quality Baryta papers available, they provide such an improved image anyway that very few manufacturers are including OBA with their Baryta papers now. The OBA type of papers are just too brilliant, making one's prints look too vibrant, as if the saturation were increased too much.

    Hope that helps try to clear up some of the confusion surrounding UV cut/OBA.

  4. #4
    Member PanozJani is on a distinguished road
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    Quote Originally Posted by shampa View Post
    AFAIK, the UV cut filter only affects the illumination, not the reading so should have no effect on monitor calibration.

    But I agree for print profiling the non-UV cut is superior. Even better is something like an i1sis that can simultaneously measure with/without UV
    It might be that this is an example when theory doesn't model the real world perfectly.
    In theory UV cut filters are perfect and they cut only the UV portion of the emitted light. But in the end I was speaking of my real world comparison of two fairly new i1Pros.

  5. #5
    aaron125
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    I'm not sure they're even that good in theory, let alone practice. There can never be any such thing as a UV *only* filter, it simply is not possible to be able to filter any part of the electromagnetic spectrum with anywhere near such precision.

    What is essentially being asked is like asking for a colour filter to cut all green wavelengths of visible light - but how can one determine precisely the exact wavelength in nm for which green starts & finishes? It cannot be something like start at e.g. 507nm & stop at 592nm because no visual system is so accurate. Certainly no person could ever say exactly where any individual colour starts or finishes because when looking at a full colour spectrum, either in reality through a prism or rainbow or on a computer screen, each colour just flows into the next. Can anyone say where exactly green turns into yellow?

    It is for these reasons that a UV cut filter of any description can never filter just and only UV and nothing more (or less). There is absolutely no difference from UV to visible light to x-rays & radio or microwaves except how fast the photon is vibrating, it's wavelength. That's why I made the analogy with colours because this clearly illustrates how difficult the whole UV cut filtering business is & why it's likely more advantageous to do an UV filtering in software.

    Remember too, that the light used for actually viewing the UV affected OBA containing paper will obviously still have UV in it. So it's cut from the measurements but is still there when the product of said measurements will physically be viewed & used. So maybe it's like 'cutting off one's UV to spite one's image'?

    Certainly an interesting discussion though.

  6. #6
    shampa
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    Quote Originally Posted by aaron125 View Post
    Unfortunately you are incorrect in your assumptions regarding how UV cut works. It has absolutely nothing whatsoever to do with the light source.

    example: i1 Pro UV cut spectro
    In an i1-cut, or any other brand UV cut spectro, the UV cutting takes place by means of a filter which removes (cuts) a portion of the spectrum, mostly cutting in the UV range of frequencies. This is performed by a physical filter, a piece of coated glass usually. That is also why UV cut cannot switched on/off in an i1Pro - if it were something in the light source then every UV cut device could also be a non-cut device by changing the light but as explained, UV cut has nothing to do with the illumination.

    It is always a much better idea to measure as much as possible, so do not cut UV, and then if desired, perform UV cutting in software like some apps are currently performing. The problem with UV cut devices is that it is cutting the UV before the UV is able to be measured. So how does one know exactly how much UV is being cut? It isn't disclosed on any device's specification sheet, nor do manufacturers seem to be willing to provide any detail either. Please let me know if I am mistaken, would be very interested to find out exactly which part of the spectrum is being cut & by how much.

    The problem with UV cut devices is also that they don't really seem to work all that well. Because the UV is cut before being detected, this in effect is similar to changing the light source. This is not a good idea because the paper with the OBA included will just about never be viewed or illuminated by any source which has no UV or very little UV in it's spectrum.

    Best solution is also the simplest. Just don't use media with OBA. These type of papers are far too bright, white, blue, etc. to be effective for fine art prints. With the abundance of extremely high quality Baryta papers available, they provide such an improved image anyway that very few manufacturers are including OBA with their Baryta papers now. The OBA type of papers are just too brilliant, making one's prints look too vibrant, as if the saturation were increased too much.

    Hope that helps try to clear up some of the confusion surrounding UV cut/OBA.
    Yes, the UV cut is a physical filter - in front of the light source! It makes absolutely no sense to cut the UV in front of the sensor, as it divides the light up into its component frequencies anyway. The point is that the light source doesn't emit UV, so as to not excite the FWAs.

    But when in transmissive mode the i1 isn't emitting any light, UV or visible, so the filter is irrelevant. (Nor is any UV emitted by the monitor relevant, since you don't see it and the profiling software thus rightly ignores it.

    Quote Originally Posted by aaron125 View Post
    I'm not sure they're even that good in theory, let alone practice. There can never be any such thing as a UV *only* filter, it simply is not possible to be able to filter any part of the electromagnetic spectrum with anywhere near such precision.

    What is essentially being asked is like asking for a colour filter to cut all green wavelengths of visible light - but how can one determine precisely the exact wavelength in nm for which green starts & finishes? It cannot be something like start at e.g. 507nm & stop at 592nm because no visual system is so accurate. Certainly no person could ever say exactly where any individual colour starts or finishes because when looking at a full colour spectrum, either in reality through a prism or rainbow or on a computer screen, each colour just flows into the next. Can anyone say where exactly green turns into yellow?

    It is for these reasons that a UV cut filter of any description can never filter just and only UV and nothing more (or less). There is absolutely no difference from UV to visible light to x-rays & radio or microwaves except how fast the photon is vibrating, it's wavelength. That's why I made the analogy with colours because this clearly illustrates how difficult the whole UV cut filtering business is & why it's likely more advantageous to do an UV filtering in software.

    Remember too, that the light used for actually viewing the UV affected OBA containing paper will obviously still have UV in it. So it's cut from the measurements but is still there when the product of said measurements will physically be viewed & used. So maybe it's like 'cutting off one's UV to spite one's image'?

    Certainly an interesting discussion though.
    It doesn't matter that the UV filter cuts out some blue as well. It gets normalised when the spectro is calibrated. (although you will get a higher level of noise in the blues)

    And yes, it is cutting off one's UV to spite one's image, which is why I don't recommend the UV-cut model. It was a simple attempt to solve the problem, but software compensation works much better.

    Quote Originally Posted by PanozJani View Post
    It might be that this is an example when theory doesn't model the real world perfectly.
    In theory UV cut filters are perfect and they cut only the UV portion of the emitted light. But in the end I was speaking of my real world comparison of two fairly new i1Pros.
    As above, it doesn't matter that the filters are not perfect.
    i1s are notorious for having poor inter-instrument agreement. It is probably just luck that you get better results with your non-UV-cut model on a monitor calibration.

  7. #7
    aaron125
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    Thanks for clearing that up for me shampa

    Indeed you are correct shampa, the UV filtering is performed on the lamp inside the i1Pro. I had always thought that way is a stupid way of filtering the UV, still do. But then I don't think it's a good idea to be filtering the UV anyway.

    The filtering should be performed on the measurement side of things because doing it on the lamp means the OBA won't be activated/excited/turned-on when measuring with an i1Pro UV but it IS still there when the actual media being measured is used in practice, where the UV is still in the light source, therefore activating the OBA & bringing the whole problem back to rear its ugly head again.

    Are you aware of any specific reasons why the UV filtering is done on the lamp & not on the diffraction grating shampa? What about the newer i1Pro that have an LED lamp, not Tungsten? The LED lamp emits very little UV, so would seem somewhat illogical to try to filter something which really isn't even there in the first place.

    But then this is all just a curiosity for me, I just don't touch papers which have OBA so for me is a non-issue.

    Appreciate your correction of my mis-correction of you shampa.

  8. #8
    shampa
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    Yes, you are correct that doing it on the lamp side means that OBAs won't be excited - that's the whole point.

    As paper with high OBA became more popular, the instrument manufacturers noticed that they would give readings that subjectively looked too blue even though the numbers matched. (This is probably due to the way our colour perception adapts)

    The response was to filter out the UV in the light source so as to not excite the OBAs that were causing measurements to come out blue. Now, under lighting with no UV, the colours match. Head in sand; problem solved!

    But as you know real world lighting often does contain UV, even many D50 proofing setups do. Now everything looks too yellow, although not as objectionable as when it it was blue.

    Finally someone realised that from a spectral reading of paper-white with UV it was pretty easy to estimate how much of the light was coming back from the OBAs. Once that is known it can be compensated for and the appearance of the paper simulated for any lighting source.

    Now any decent print profiling software can compensate for OBAs provided you have a spectro that emits UV.

    There is nothing to gain by filtering on the diffraction grating. Any problems caused by UV in the light source have already occurred, and since the spectro separates the light into its frequencies any UV coming back into the instrument does not effect the measurement.

    I was not aware that the newer i1Pro uses LED illumination. That's a shame. Do you know if they are still labelled rev.D or are they rev.E or some new model number?

    Unfortunately, in offset printing I do not have the luxury of going OBA-free. I am still expected to get colours matching.

  9. #9
    Member PanozJani is on a distinguished road
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    Quote Originally Posted by shampa View Post
    i1s are notorious for having poor inter-instrument agreement. It is probably just luck that you get better results with your non-UV-cut model on a monitor calibration.
    I agree with You on "luck factor", but as i recall i was measuring the results with the spectro i was using for calibration to exclude the differences between the devices...

    I'll repeat my test, and report back the results...

    And just to get back on topic, one should not provide profiling services with UVcut i1.

  10. #10
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    to cut UV-cut or not, filter vs calculation vs light source...

    since most of us use fogra supplied measurement data and aim for those, shouldn't we use the same measurement tools and settings? the gretag spectroeye is the most recommended one, no uv cut, but iso standard paper shouldn't feature optical brighteners.

    if you measure all aims and targets yourself and never use supplied measurement data - it don't matter what you do as long as your device is stable in itself since you take the most important uncertainty factor out of the equation - your measurement tool!

    good read [URL="http://qualityinprint.blogspot.com/2010/05/top-reasons-why-color-instruments-dont.html"]http://qualityinprint.blogspot.com/2010/05/top-reasons-why-color-instruments-dont.html[/URL]

    enlightened me on a lot of issues i used to have. NOT EVEN CERAMIC TILES ARE STABLE!

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  12. #11
    Moderator super silja will become famous soon enough super silja's Avatar
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    for people who read this and don't know what we speak about
    if you make profile for media with optical brightener (and without UV compensation, your proof will look too yellow

    UV CUT or NOT that is a question
    you already say everything, but without conclusion (because there is no conclusion)
    for proofing different vendors use different solution
    KODAK for proof use always HW UV CUT. Who can say that they are wrong?
    EFI recommend - for proof NO filter, for production UV Cut ( god compromise)
    Tetrapak for example use UV CUT for proof. Again - who can say that they are wrong?

    according monitor calibration UV-NON UV
    i1 is calibrated in emission mode.
    you have bad device if you have different readout with UV/NO filter combination

    when we speak about paper.
    almost all vendor have proof paper with low OBA
    it's hard to find offset paper without OBA, if you know please post it

    @jani
    So making profile with UV or without filter is question of sw solution.
    i am sure that all sw solution for icc profile generation know how to handle measurement w/wo UV filter
    i'am not sure that you need to make proof on VUTek.
    do you have measurement and QC of monitor? please post it.

    and small note
    according ISO. Light emission should be without UV. In that case reemission is without UV.
    in that case you don't need UV filter
    ps
    if you have any problem please share with us what you do (change) and if you find solution please don't say "Problem gone"
    Last edited by super silja; 08-27-2011 at 04:25 AM.
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    |p|o|w|e|r| |t|o| |b|e| |y|o|u|r| |b|e|s|t|
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  13. #12
    Nemesis
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    ^

    Have you seen one of these ---> http://www.scheufelen.com/en/paper-brands/heaven-42.html

  14. #13
    Moderator super silja will become famous soon enough super silja's Avatar
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    Quote Originally Posted by Nemesis View Post
    ^

    Have you seen one of these ---> http://www.scheufelen.com/en/paper-brands/heaven-42.html
    thanks for supplied information
    i'am curious to know what you see in supplied data


    SAMPLE_ID SAMPLE_NAME CMYK_C CMYK_M CMYK_Y CMYK_K XYZ_X XYZ_Y XYZ_Z LAB_L LAB_A LAB_B
    END_DATA_FORMAT

    1 "g1" 0.00 0.00 0.00 0.00 81.33 82.97 81.23 93.00 2.59 -11.02
    9 "Y15" 0.00 100.00 0.00 0.00 33.34 18.49 16.50 50.09 66.08 -3.01
    73 "P11" 100.00 0.00 0.00 0.00 16.99 22.99 52.98 55.06 -26.00 -50.02
    649 "J11" 0.00 0.00 100.00 0.00 66.45 69.90 9.55 86.95 -2.10 80.02
    1260 "b13" 0.00 0.00 0.00 100.00 5.67 5.76 4.58 28.81 1.31 0.99
    +-+-+-+-+-+ +-+-+ +-+-+ +-+-+-+-+ +-+-+-+-+
    |p|o|w|e|r| |t|o| |b|e| |y|o|u|r| |b|e|s|t|
    +-+-+-+-+-+ +-+-+ +-+-+ +-+-+-+-+ +-+-+-+-+

  15. #14
    Member PanozJani is on a distinguished road
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    sorry

    @jani
    So making profile with UV or without filter is question of sw solution.
    i am sure that all sw solution for icc profile generation know how to handle measurement w/wo UV filter
    i'am not sure that you need to make proof on VUTek.
    do you have measurement and QC of monitor? please post it.
    I've redone the monitor calibration testing - on my current setup (eizo s2111w) and with i1Profiler (1.1.1), resetting the monitor to factory default settings (except for brightness).

    THERE WERE NO SIGNIFICANT DIFFERENCES between the 3 instruments and the results (2 of them non UVcut) - so no need for posting QC data.

    So sorry for my previous misleading post!

    Probably i was less careful when i was doing the previous comparison.
    Last edited by PanozJani; 08-31-2011 at 11:53 PM.

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  17. #15
    Rav
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    Using a Baryta paper like Ilford Gold Fibre Silk is one solution to the issue. I’ve noticed that this paper doesn’t ‘flick’ the OB switch in ProfileMaker Pro, which indicates that no OBAs are present. I’ve measured this with a non-UV-cut i1 Pro.

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