Digital BW, The Print

Roy Harrington wrote:

>
>>Roy did the existing profiles as generics - they are not constructed from
>>actual data and assume a linear greyscale.  My wish would be for a little
>>program that, say, read a text file of actual data.  First variable would be
>>for the number of observations making up the greyscale readings...21, 51,
>>...256.  Then a list of observations printed by the a particular printer
>>with a particular workflow (Epson Adv B&W, QTR, BO....) as measured say with
>>Quickread (or similar) in order to construct the kTRC tag.  The list would
>>also pick up the media white point wptp tag.  Then you have an ICC profile
>>for your printer, your workflow and your ink etc.  Conceptually it is not
>>difficult.  Roy or the like can tell us how difficult it would be to
>>program....and to find the time to do it..  :-)
>>    
>>
>
>Hi Steve,
>
>I've been trying a few things out in this direction.  Unfortunately just changing
>the wtpt doesn't seem to do the trick.  What seems to be necessary is to do a
>"White Point Compensation" in the profile itself -- analogous to the BPC that the
>color engine does.  I have a few more ideas to try.
>
>Roy
>  
>
I know that the profiles are generic and that the underlying (custom) 
linearisation per printer/inkset should take care of a basic layer to 
use the generic profiles on top off. That it is still a compromise is 
also correct and custom profiling on top of a custom 
ink-limited/linearised-ink/paper/resolution set printer should be 
better, especially as the Dmax + the white point per printer/paper could 
vary and the generic profile will not adapt to that. On the other hand 
we shouldn't forget that many do not have the extra hardware to get the 
best custom calibrated and profiled output. So a bit more choice in 
generic profiles may be good for them while QTR should develop to even 
better control where possible.

Finding an affordable hardware solution for linearising and profiling to 
get beyond that stage of generic profiles and hand luck linearisation is 
a next step. Scanners have shown to be usable already and digital 
cameras may be another possibility. It would be good to have some 
information collected on what works with scanners and how it is done. 
The dynamic range in reflective scanning of today's flatbed scanners is 
sufficient most of the time. The geometry of the lamp and the sensor may 
not be correct though to compare the readings with densito- or 
spectrometers. It must be possible to make tables for the scanners that 
are used by the list members. Using the right methods in target 
printing/scanning it should be possible to get near the results of more 
dedicated instruments.

Another thing that could be added to the B&W profiling software is the 
possibility to use data from 3 readings, either from 3 targets printed 
or from 3 readings from the same target. Increasing the number of 
greyscale steps in the target may give less gain in precision than 
multiple readings from more targets. Depends on the accuracy of the 
instrument, the handling and the software interpretation. To be honest 
producing a 256 step target goes beyond the capacity of many printers I 
think and what has to be done afterwards in getting a profile from so 
many shades may be worse as a result. What would be interesting is an 
iteration feature, where a new target printed with the custom 
linearisation + custom profile delivers data that can be added to the 
profile for fine tuning. Then the printer setup has to have more 
consistency than the iteration feature delivers. I wonder whether that 
is possible with the desktop printers. Increasing the target steps in 
both linearising and profiling to 70 steps at most + an iteration of a 
200-256 step tablet to one of them may be a solution. For the densito- 
spectrometer and the software it should be better/easier if that was 
done in the linearisation. The profile could then probably be based on 
far less than 70 readings.

Ernst