Digital BW, The Print

Nick,

thanks for the thoughtful review of IJC and its unique "take" on controlling ink. 
I agree with you that if you see it from a traditional prepress perspective, it 
won't conform to what we expect from color profile-making programs. This one 
is built purely on the logic of how best to lay down a grayscale and partition 
the gray inks. 

Some responses to your comments:


By that I mean that traditional cmyk
> curves relate to actual ink percentages as used to print and the ink limit
> is built in to the curves.

As you know those percentages are derived from the ink coverage of a given 
dot area of a traditional screen (when half that dot is covered with ink we call 
it 50%). In the case of IJC, the percentage numbers merely refer to a place on 
a grayscale from 0 to 100.


> 
> In the IJC app it seems ink limiting is handled behind the scenes somehow,
> where one dials in the appropriate step value and that value determines the
> ink limit.

IJC lets you see the effects of letting the printer run with the tap completely 
open, i.e. deliver all the ink the hardware  can handle, even if it runs off the 
paper !  It allows you to print a grayscale for each ink under that state, so you 
can see how much ink your paper can take, then assign a limit of your 
choice. That's a crucial feature in IJC that allows for true determination of the 
maximum density of a paper/ink combo. In that sense, it does not do 
something "behind the scenes", but rather hands the control to you so you 
can dial a value from 1 to 26 based on the results of the test print above. 

Again, it doesn't really match the traditional prepress notions of "total ink" or 
UCR. For that matter, it doesn't even address the effects of the total ink that is 
layed down at maximum black when more than one ink may be running at the 
same time. The only way to find out what happens if you overload the paper 
by - for example - running full "cyan" _and_  full black at the 100% patch, is 
trial and error and good densitometry. In traditional prepress terms we would 
have called that 200% total ink (100%cyan+100%black) - a limit well below 
even newspaper applications. In the case of inkjets, however, things are 
very different. 200% with dyes may indeed produce a deeper density than 
black alone, but 200% with pigments would be a disaster and dmax will suffer. 

IJC completely bypasses any notion of "percent"  laydown. It gives you a 
way to simply determine how much ink each head will lay down at a given 
point in the grayscale. It does this by showing a 0-100% scale under the ink 
curves. As you place and move a point up or down the curve, more or less 
ink is delivered for those parts of the grayscale that are affected. Simple as 
that. This has nothing to do with the percent of dot coverage as used in 
prepress.

Unfortunately, IJC ommits to give us a value on the vertical axis of that curve, 
such as a scale of 0-255, so we know numerically how much we move the 
points by. Worse yet, it also ommits a scale of 0-26 running in parallel to the 
0-100% scale at the bottom. Such a scale would correspond to the 26-step 
patches that IJC prints for measuring. Since the patches only have numbers 
from 0-26, it would be nice to have these numbers under the ink curves . 
Instead, we now have to print a scale and using a pencil (!!!)  write down what 
percent on the grayscale each patch corresponds to, so we can find it on the 
percentage scale under the ink curves. Of course, you only need do this 
once and then stick it on the side of your monitor (!!), but it makes for an 
inelegant solution.

 
> Once this new limit is applied it is not reflected by a redrawing of the
> crossover curves. 

Choosing an ink limit causes the effects of the whole ink curve to increase or 
decrease  - as if the whole thing went up or down the grid. It would't cause a 
redraw because of the logic of "limits" as it applies to inkjets vs prepress (as I 
discussed above).  Changing ink limits after you have arrived at a good 
curve, gives you a chance to reduce or intensify an ink while maintaining it's 
"shape". This is almost an unintended "feature", very useful in many 
situations. IOW, besides the limiting function as I discussed earlier, these ink 
limits are an added control over and above the curves. An example would be 
the use of a toner. You decide how you want it to behave at each point in the 
grayscale, then adjust overall intensity using the limits. Very cool in pratice!


> 
> In addition the "ink color" patch values seem hard to determine, one is left
> having to visually match them to actual ink colors somehow?

Indeed. Apparently the "wysiwyg" intentions of the  preview that the scales 
give you, could not be materialized. As a result, these are useful as an 
overall "icon" of what curve corresponds to what ink. You pick a color from 
the Apple color picker to assign to each ink by simple eyeballing. It helps you 
only to know that this ink starts and ends here and to see it in relation to other 
inks. It has no effect on the profile you save.

 The composite grayscale preview is also "inaccurate" for showing banding 
and the like, but useful for showing gross error or if you have turned off the 
wrong ink, etc. I was never concerned with using these previews to base 
precision moves on the curves, but they offer useful feedback overall.



> 
> The linearization feature seems superb, very well thought out. It would be
> nice if this could be used "stand alone" for linearizing a variety of
> printing behaviors, not just OPM. 

Not a bad idea - but for that to work, the Aims would have to be editable. As it 
is IJC internally generates a set of 26 density values that represent an ideal 
transition from the max black to paper white (as read in a densitometer from 
the printed target). Not every program, user or image need agree with that 
ideal. But if the aims were user-defined, the internal engine in IJC could 
indeed "linearize" to those  numbers instead of the current built-in "ideals". I 
think this would be a good feature for future IJC versions, anyway.  


> I think it is also important to add that the "print dialog" is hands down
> the best I've ever seen. It might be nice to pull the single vs multi pass
> option out of preferences but other than that it's great.

I agree.... but would like to see simple capabilities added, such as 90 degree 
rotations of the image, user-defined page size, typable image dimentions and 
printable area preview. But we are only in v.1xx. I am sure there is more to 
come down the line.

Thanks for sharing your views and feedback on IJC. 


Antonis