[Openicc] Drop size calibration

[Hal V. Engel]

On Friday 01 February 2008 06:04:34 Lars Tore Gustavsen wrote:
> On Feb 1, 2008 12:35 AM, Hal V. Engel <hvengel at astound.net> wrote:
> > No I took this offlist since there were only two people that expressed an
> > interest in it.  But if the list feels that this is not too far out side
> > of the lists scope I can also post this here.  (If not, Lars, I will send
> > you a copy of the measurement files and spreadsheets and also include you
> > in any responses)  The off list thread has generated some interesting
> > information about the measurements and the resulting plots.
> >
> > Hal
>
> Thanks Hal.
>
> It was quite interesting reading, and as usual it was over my head.
> Anyway I found these sentences here (pleas forgive me for posting this
>
> publicly):
> >"Hal writes
> >In my earlier testing I also noticed that these curves seemed to change
> >significantly when I switched ink carts.  So if there were a calibration
> >utility it would make sense to recalibrate whenever a cart was changed."
>
> I guess the same would apply for other printers than the R2400. 

I do not have any reason to believe that this does not apply to most if not 
all ink jet printers.  For some printers, like those with the nozzles built 
into the ink carts, this might be even more of an issue.

> This 
> means as far as I can se that we really need a simple calibration
> method for our printers.  

If you are concerned with high levels of consistency/repeatability then I 
would say yes.  For your average user maybe not.  Besides your average user 
is not likely to have the measurement equipment needed for this.

> And until then your spreadsheet is a really 
> nice guide for gutenprint curves adjustments.

I put the spreadsheet together to help me visualize what was going on and to 
see how my adjustments affected things.   It does not give you any guidance 
on what those curves should actually look like (beyond of course being 
smooth) or exactly what adjustments need to be made to correct specific 
issues in the curves.  

For example Robert looked at the curves and based on his experience was able 
to say that perhaps there needed to be changes made to some of the light/dark 
ink transitions and he was able to say specifically what needed to be 
adjusted.  Looking at the curves I was able to surmise that some of the curve 
issues were related to the light/dark ink transition but this was mostly 
because there were none of those issues in the yellow curve which only uses a 
single ink.  I also had no idea what kind of adjustment would have improved 
the curves. 

In addition I don't know how much variation there is from printer to printer.  
That is some of the problems I was seeing in the curves of my printer may not 
show up in your R2400 or the one Robert has.  Perhaps you could run a set of 
test measurements using the same settings I did and drop those into the 
spreadsheet.  If the curves look like mine then this is likely not something 
specific to my printer.

Hal