Inkjet photoprints too yellowish due to optical brighteners?

[Calibrero]

Hi all,
When I profile my inkjet photopaper, the resulting prints are too yellow. I understand that the optical brighteners in the coating of the paper are the cause of the problem. The manufacturers of the paper add a bit of blue to the coating so that it looks whiter. The blue is not visible for human but the spectrophotometer measures it as too blue and so the profiling software adds yellow to compansate for this.

There is a UV-filter on the DTP70 but it makes no difference if I use it or not. At least, not to my eye... Given the fact that I have to stick to this specific paper, what are my options?

• Should the UV filter in the DTP70 make a difference?
• Is there maybe some software solution for this?

My setup:

• HP Z6100
• Non-HP photopaper
• x-rite DTP70
• Monaco Profiler 4.8.3 Gold Edition

Thank you for your advice!

[meddington]

[

[*]Should the UV filter in the DTP70 make a difference?

If there's is enough OBs in the paper, It should make a difference in the measurements. What is your paper white point measurement both with and without UV filtration?

UV filtration is often not a complete solution to the issue though, as it doesn't take into account several other factors (viewing condition...i.e. the amount of UV in your lighting, the amount of OBs in the press stock, etc.)

[*]Is there maybe some software solution for this?

There is, but most are not sufficient. Xrite's OBC module is a nice solution, but requires an Isis spectro. The best solutions for OB issues include visual analysis (as does OBC)...afterall, its more than a measurement issue...your viewing conditions have to be taken into consideration.

You might, however, find the solution is as simple as a few tweaks to the profile.

[Calibrero]

What is your paper white point measurement both with and without UV filtration?

without UV filter
X 0.856
Y 0.884
Z 0.770

with UV filter
X 0.853
Y 0.885
Z 0.746

Doesn't seem like much of a difference?
Do you know if it's possible to tweak the profile with Monaco Profiler Gold or is there another solution (preferably free ;-))

Thank you,
Peter

[Correct Color]

I've seen more than a few instances of profiles on Photogloss type stocks from aqueous machines having a yellowish cast simply because the patches were read too soon. It can take these papers a good long while to completely gas out and settle down.

If you're not doing it, try letting your patches dry overnight before reading them. That just might resolve your issue.


Mike Adams
Correct Color

[meddington]

without UV filter
X 0.856
Y 0.884
Z 0.770

with UV filter
X 0.853
Y 0.885
Z 0.746

Doesn't seem like much of a difference?

That translates to CIELab values:
No Filter
L 95.3
a* o.68
b* -3.49

With UV filter
L 95.32
a* -0.6
b* -1.37

The change in the b* value would be the result of the UV filter, so looks like its doing its job...UV filter blocks the UV component of the spectro light source, preventing excitation of the paper's OBs to some degree. This might help some, but it doesn't prevent the excitation of the OBs from your viewing lights, so may not be sufficient.

Do you know if it's possible to tweak the profile with Monaco Profiler Gold or is there another solution (preferably free ;-))r

Should certainly be possible with the Monaco Profiler Editor...white point edit or curve adjustment. Profile editing is a bit cumbersome, but its possible. You might take Mike Adam's advice into consideration as well.

[TerryWyse]

In MonacoPROFILER there are some adjustments you can make when building the profile....the only catch being that it's only for the perceptual rendering intent. All the same, I'd try adjusting the "Neutral Gray Axis" (or is it labeled "Paper Gray Axis"?) in the Perceptual Options. Leaving it at 0 makes no adjustment and keeps neutral grays "relative" to the paper....sliding it to the right starts pushing the neutral rendering towards a more "absolute" neutral rendering. You have to move it fairly aggressively to get much change.

Your paper's L*a*b* values (thanks Mike for doing the convert from XYZ to Lab) definitely point to the presence of OBAs in your paper.... anytime you see the a* decrease and the b* increase when using a UVcut filter, that's a dead giveaway you've got OBAs.

From everything you're saying, I'm placing my bets on your viewing conditions. I've been dealing with some photo papers lately with a fair amount of OBAs and they've rarely required any special treatment during measurement or profiling...but I'm pretty much using 5K lighting everywhere in my office....and I'm using an iSis which is different animal (spectrally-speaking!) than the DTP70.

Good luck!

Terry

[Calibrero]

Thank you guys for helping!

If you're not doing it, try letting your patches dry overnight before reading them.
Correct Color

I followed your suggestion and let the patches dry for 24 hours. The values I read (with UV filter) now are:
X 0.850
Y 0.881
Z 0.744

The print is still too yellow/green. I brought the print outside in daylight, same story.
My office has about 5300K lightning by the way.

In MonacoPROFILER there are some adjustments you can make when building the profile....the only catch being that it's only for the perceptual rendering intent. All the same, I'd try adjusting the "Neutral Gray Axis" (or is it labeled "Paper Gray Axis"?) in the Perceptual Options. Leaving it at 0 makes no adjustment and keeps neutral grays "relative" to the paper....sliding it to the right starts pushing the neutral rendering towards a more "absolute" neutral rendering. You have to move it fairly aggressively to get much change. [.......]

I found that option, thanks. It doesn't work for me however. I've put the slider all the way to 100% but again the print is too yellow/green. In Onyx ProductionHouse the CMYK reading are almost the same with the two different profiles, neutral axis set to 0% and to 100%. There is a slight decrease in yellow, so it works, but just not enough to get a good print. I have used perceptuel rendering.

It's slightly frustrating that I can get fairly good prints when I use the Windows printerdriver of the Z6100, direct printing, when I don't use ProductionHouse and colormagement :-)

I think I have to look for another photopaper.... there are no funds for another spectro meter.

Thanks again!

[Correct Color]

You didn't mention earlier that you were using a RIP. Are you doing halftone or contone profiles with Onyx?

[Calibrero]

I'm sorry that I didn't mention it.
I use contone profiles.
But, if I use the custom made ICC profile in Photoshop (RGB desatured image, convert to CMYK) and go by the profiles in Onyx (All Profiles Off), I have the same problem by the way...

[yannb]

Hello,

Try building your CMYK output profiles with a more agressive GCR.

Regards,
Yann