Optical Brighteners - How to best manage the issue

[bmcvey]

Hello all,
I am looking for a technique for best managing the measurement differences associated with media containing optical brighteners and relating the pass/fail criteria to the contract proof that does not contain any optical brighteners.
So far I've tested M0 & M1 but the measurements are being altered by the optical brighteners.
In my example the white point measures L95, A1, B-5. This visually looks white with a very slight red cast however these LAB values are purple which in turn makes purple ICC profiles and purple contract proofs unless I manually correct out the white point.
M2 does remove the effect producing a representative LAB value (L94.1, A0, B0.6) however M2 removes the UV filter.
I could blend the 2 & use white point correction tools but concerned about the impact up the tonal range.
All advice would be helpful.
Thanks,
Bob

 

[Bret Hesler]

Is your contract proof substrate free of optical brighteners? You will have to switch to something with optical brighteners to match the optically brightened printing paper.

Most of the papers I print measure, in M1, in the range of -6b* to -7b*, with the brightest near -10b* My proofing substrate is close to the brightest paper, and i match the others with a little bit of paper simulation.

 

[bmcvey]

Is your contract proof substrate free of optical brighteners? You will have to switch to something with optical brighteners to match the optically brightened printing paper.

Most of the papers I print measure, in M1, in the range of -6b* to -7b*, with the brightest near -10b* My proofing substrate is close to the brightest paper, and i match the others with a little bit of paper simulation.

Thanks Bret,

I don't like the inaccurate measurement you get with paper that has optical brighteners for contract proofing which is why I've standardized on not having it in but you do raise a good point in aligning the media's. Our industry is tricky, we also have many substrates we print on that do not contain optical brighteners so I am looking for a way by measurement to be accurate in dealing with them.

Bob

 

[Bret Hesler]

I don't consider it an issue of inaccurate measurements, but rather an incompatibility between OB free proofing papers and OB rich printing papers. You can't simulate the brightness of a heavily brightened paper by adding cyan and magenta to an OB free paper. As you stated, you get purple.

I did two setups from the same press run with an i1Pro2, in M0 and M1, and saw little difference with my optically brightened proofing paper. We do commercial printing and ad production, and very little of what we print is OB free. We proof newsprint on newsproof stock, and SWOP3 on OB free paper. The newer Gracol 2013 and Fogra51 characterization data are much more indicative of the blue-white, brightened sheets that we actually use. As these replace Gracol 2006 and fogra39 in the market, brightened proofing papers will not only be common, they will be necessary.