QTR-Quadtone RIP

Paul, thanks again for your help.

I'm still getting not very far and am a bit concerned about using up paper at £1.30 (about$2) a shot
> > After the initial calibration and second calibration prints, I am getting
> > a Dmax of 1.60 from the Black at 25% default ink limit.,
> >
> That is low for H. Photo Rag.  Is that what your full Calibration Print at
> 100% showed as the darkest?  I just looked at an old 1400 H. Photo Rag QTR
> profile that used Eboni MK, and the ink limit was 30 with a boost to 40.
>  This produced a dmax of 1.71.

I can get density of MK up to 1.71 at 35%, however the rate of rise on the plot of calibration densities here is very low.  Plotting densities on Excel shows a steep rise from paper white (0.02) up to 25% MK giving 1.62 at this point the plot shows a rounded transition to near flat.  1.71 is the start of the flat part.

> both C and M came in at 57% of that with Density of 1.25 (both are the
> > same).
> >
> That sounds like it should be within range.  However, if you are getting
> posterization or too low a slope in the gray ramp near the 100%, you might
> want to lower the C and M ink limits.  A dark gray at 30 density is what I
> see in the old (not UT14) profile I'm looking at.

I'm not quite sure what you mean by posterisation.  On my 21 step prints for linearisation, the 100% step is very black and stands out from the 95%.  The 95% steps for cool and warm have a tint towards their respective "colours" and the 100% just seems black.  Is this posterisation?


> In looking at your linearization numbers, it seems like the 95% to 100%
> pre-linearization gap is more than I'd expect.  The 90 to 95% gap is too
> small.  I wonder if your C curve was going flat there.  You might be able
> to correct this by backing off on its ink limit.  Set the midtone ink
> limits were the inks still have a good positive slope to them.

I felt the jump to 100% seemed a bit big and out of step with the other increasing values.  I have brought the C and M limits down to 40% (of the MK value, now at 23% with boost to 28%) and plotting the density readings now shows a lift at the top end of the plot (when printing the new profiles on a 21 step wedge). However there is still a steep jump from the 95% step to the 100%.  (maybe I shouldn't have put the boost in at the same time as lowering the C & M values?). 

It seems a bit counter-intuitive that lowering the second grey value makes the top of the wedge darker, but I still have a lot to learn about what's going on. 

On a calibration print using the Inkseperation6.tiff, with the calibration set at 23%, there is no flat spot on C or M, they both keep rising in a smooth curve, not even levelling out.

> LC was 46% of C meaning 26% in the ink descriptor (at Density .80), if I've
> > got this right and LM was 48% of M being 27% in the descriptor (Density
> > .85).
> >
> It's OK only if it works!

Would I be correct in assuming, lowering the 3rd grey value would actually darken the lower end of the printed scale?

 regards

Ross