What are Hahnemuhle 'ab charge' profiles?

[narikin]

For my Epson printer I see two profiles for Hahn Photo Rag UltraSmooth for download - both a regular one and another with 'ab Charge 476910' in the name. What's that about?

Thanks

[Lessbones]

knee jerk reaction on seeing that is maybe someone had altered the white point of the profile and was using the name to indicate as such-- in which case "Charge" should have been "Change" and .476 and .910 could correspond to the "a" and "b" values in Lab respectively.  This is really close to neutral, so I'm not quite sure why you would do that.  It also could mean 4.76 and 9.10 which would be very far from neutral, so who knows.  Or something else entirely-- you'd have to compare the profiles in something like colorthink pro to figure out what the difference is

[digitaldog]

Upload both profiles to something like Dropbox and I'll look them over in ColorThink Pro 4.

[digitaldog]

The profile 476910 has a slightly larger gamut volume (500,859 vs 493,798). The white point differs yes. It has a larger CLUT table (37 vs 32). Both were built by X-rite software. The Neutral Rendering curves are nearly identical. 476910 was produced in in 2018, the other 2014. Both were built with 918 patches. Both used M0 measurements.
What does it all mean? Nothing until you print the same color reference image with both, preferably using the Perceptual rendering to figure out which you prefer. When I compare the measurement data of the two targets and produce a deltaE report:

dE Report

Number of Samples: 918

Delta-E Formula dE2000

Overall - (918 colors)
--------------------------------------------------
  Average dE:   1.36
      Max dE:   6.90
      Min dE:   0.36
   StdDev dE:   0.56
95th %ile dE:   2.33

Best 90% - (825 colors)
--------------------------------------------------
Average dE:   1.23
    Max dE:   2.05
    Min dE:   0.36
 StdDev dE:   0.39

Worst 10% - (93 colors)
--------------------------------------------------
Average dE:   2.48
    Max dE:   6.90
    Min dE:   2.05
 StdDev dE:   0.62

--------------------------------------------------

In Gamut - (0 colors, 0.0%)
--------------------------------------------------
Average dE:    n/a
    Max dE:    n/a
    Min dE:    n/a
 StdDev dE:    n/a

Out of Gamut - (918 colors, 100.0%)
--------------------------------------------------
Average dE:   1.36
    Max dE:   6.90
    Min dE:   0.36
 StdDev dE:   0.56

--------------------------------------------------
--------------------------------------------------

[narikin]

Thank You Andrew!

Strange how they are so close, yet indeed different.

I have nothing to add other than cotton rag paper has improved its white point over the years, so an 'Ultrasmooth' base from 2018 might be slightly tweaked from the 2014 one, so... they re-profiled maybe?

Random guess on my part, though certainly on Ernst Dinkla's 'Spectrum Viz' you see different plots for older vs newer samples of the 'same' paper - mostly in the blue end of the spectrum for OBA free rag papers

[digitaldog]

they re-profiled maybe?

That, most certainly.
The bStar of the paper white varies from 6.96 to 4.17, which may be the reason for the reprofiling. The Lstar and aStar is nearly identical.

[Ernst Dinkla]

That, most certainly.
The bStar of the paper white varies from 6.96 to 4.17, which may be the reason for the reprofiling. The Lstar and aStar is nearly identical.

There was a change in the paper coating AFAIK. I have a roll here that was purchased after that change.

Met vriendelijke groet, Ernst

www.pigment-print.com/spectralplots/spectrumviz_1.htm