Thanks Mike.  We're on the same page at least on the LOC numbers (0-16).

If there was an easy way to call in the 21 steps to the LOC to make it linear it would be great.  As it is, the spreadsheets that do this L*ab linearization stuff automatically take some step, like step 19 that goes off the straight line where all the others are dead on.  Then I have to try and figure out that gray scale step 19 (if it is towards the white end) a LOC 14 or 15 in Qimage's LOC's box?  It's really 14.48 if my math is right, but I cannot plug that in to the LOC as the scale is too small and fixed on whole numbers both.

If I could set say LOC=14.5 that would work, although takes me some math to get from that step tablet number of 19 into Qimage.  As it is, Qimage rounds down to 14 and it messes up that number which was correct based off the spectrometer's readings so that part of the curve now gets messed up when it was correct.  For piezo inks, it becomes a mess since it pulls in another gray ink tank out of 8-9 tanks.

Actually, even on a 51 step scale, if the linearization spreadsheet says step 49 is off, if I could plug in 15.4 into Qimage that would work even with the 0-16 current range in it now.  Problem with the 51 steps if a range of say 44-49 is off, then how to null it out without using a finer scale in the LOC axis range?

Some of these black inks are very finicky in the Qimage Curves I find as they also call in other colors to make them neutral.  That fading blot of Keith Cooper's newest B&W Test Image sure shows up banding if the tuning curve isn't spot on.

Aside, QuadToneRip (QTR) doesn't work well in newest Windows and Roy seems to have abandoned it to Apple/Mac as his Windows coder never updated his compilers for newer Window versions.  It allows for a lot of curve tuning in blacks and colors of ink, I think it did more than 51 steps and maybe more as it pulled in the spectrometer readings and adjusted the curve automatically.  Just it crashes a lot in Windows 8 and Roy cannot fix it so it is a very old version now.  Windows needs a new QTR B&W printer software of some sort (hint. hint.  ).

Anyway, food for thought.  0-16 with the ability to set 1.3 (example) would be better for fine tuning with these new 21 & 51 step tablets, just a bit more math work or a spreadsheet formula to correct for entry into Qimage LOC box.

Mack

Mike, if I read your math right, the small "p" is off my 21 step chart.  Those are fixed whole numbers so Step 1 is p1, Step 2 is p2 etc. on the X-axis.

If I do the table I get this:

P0: p0                 = 0
P1: p1*0.75 + p2*0.25   = (0.75)+(0.50)  P1=1.25   i.e. (Step 1*0.75) + (Step 2*0.25) for a Qimage LOC # = 1.25     Can't input that into QU.  Rounds down to 1 only.
P2: p2*0.50 + p3*0.50   = (1.0)+(1.50)   P2=2.50    Drops down to LOC=2
P3: p3*0.25 + p4*0.75   = (0.75)+(3.00)  P3=3.75   Drops down to LOC=3
P4: p5         =    = P4 or LOC4 = Step 5
P5: p6*0.75 + p7*0.25   = (4.5)+(1.75)    P5=6.25

... etc.

Seems to be dependent on some other step than the single one I want to address, and also altering its neighbor, aside from the decimal part?

Somehow I can't see how 21 'whole numbers' off a step wedge reading can be fitted to 17 'whole number' LOC steps without some sort of decimal in the mix too?

Was trying to do this in a spreadsheet and got a math headache.  Ugh! 

______________________

Aside:

I'll attach a sample 21 step wedge (converted) JPG, but I need to reverse the Black to Zero and White to 21 for use in Qmage.  What usually happens with some cheap printers the blacks get bunched up around the 18-21 scale in the JPG.  I think my Canon 9000 II falls into the "cheap" category (Hence the need to do a quick bump off the left side of the Curve in QU as above), and the Epson 3880 addresses the issue a bit better with more balck shades of in.  Tuning the black shadows so they separate in the cheap Canon is a problem, and the i1 spectrometer tells me its blocked up too.  Just cannot refine it as well since the QU LOC range/scale is too compressed.

Don't know why 51 gray scale wedges is some big deal either, but those are out there.  Might be the 8-9 blacks in piezo inks may make the same "bunching up of black shadows" issue with a smaller 3 black inks 'color' printer; Somewhat like Canon 9000 II is to 3-black ink 3880 (Excluding the other Epson 3880 Photo Black or Matte Black since only one can be used at a time, along with the other Light Black and Medium Black.).

Keith Cooper's newest B&W Test Image has the 51 step wedge that is capable of being scanned with the i1 ColorPort software which might make it easier than reading all 51 steps individually.  Should be easier to dump the readings into a CRV file to read in the software or a spreadsheet that shows the linearization curve.  He also did a 21 step as well maybe for manual entry or the cheaper ColorMunki Photo.  Must be some standard since Kodak had 21 step wedge for decades, and Stouffer in the printer biz both.

Mack