Digital BW, The Print

Paul,

I warned you I was a bit confussed. I will lower the LC & LM to about a 6% mix 
based on your advice. It sounds likes it doesnt take much color to smooth the 
tone so I am guessing somewhere between 3% - 6% ink-base should work. I have a 
linearized carbon warm inkset using K, M,C,Y grays. This is what spured the 
thought and question of controlling the Lab A & B values using the LC & LM 
tones. 


So you are saying to consider the standard Lab color matrix as the road map when 
trying to determine what needs to be increased or decreased and how to move from 
point A to point B. Which is actually very smart advice- kinda like driving from 
NYC to LA without a map I suppose. Worse yet, driving to LA via Omaha...

I spent a lot of time last night looking, comparing, & printing different 
comparisons of K, LM, & LC last night using QTR. I discovered how to develop a 
unigue LC ramp where step 21 and Step 1 are a near match. It ramps up as normal, 
hits the mid tones, and drops to 0 at Step 21. Nothing useful but it is a key 
step in understanding the QTR Curve Creation and interpreting the curves (Show 
Curves). Much the same learning approach usng carbon, LM, & LC and what the 
output is compared to the denisty & ink limits of the individual inks.

I started using QTR specifically when I switched from UT14 to K4. The whole 
process is much easier as there are less moving parts compared to PS.

Thank you for the knowledge and advice. I am certain there will be more.

Phil




________________________________
From: Paul <roark.paul@...>
To: DigitalBlackandWhiteThePrint@yahoogroups.com
Sent: Sun, March 6, 2011 11:55:43 PM
Subject: [Digital BW] Re: Adjusting Lab A and Lab B through ink denisty

  
Phillip Kimble <grimmieoldfart@...> wrote:
>
> 
> The Eboni K4+ approach (Epson 1400) is what I am 
> currently working with to learn 
> how to manage the Lab A & Lab B:

> K = 100%
> M = 30%
> C = 9%
> Y = 6% (thinking I may change this to 3%)

> LC = 100% C (Might change this to 30% CÂ for LC)
> LM = 100% M (Might change this to 30% M for LM)

Yes,I'd make these lighter -- easier to control and less likely to show.

> 
> What I recall is one unit of LC lowers Lab B but increases 
> Lab A 

LC will lower Lab B but also lower Lab A. Cyan is in the bottom left quadrant of 
the color wheel, with a negative Lab A and negative Lab B. As an example, a 
Tiffen test strip with a step wedge and CMY color patches has a cyan with a Lab 
A & B = (-41, -47)

> 1 unit of LM increases Lab B but lowers Lab A. 

No, LM will increase Lab A. I think most of the inkjet pigment magentas have a 
negative Lab B, so they'd decrease it. The Tiffen test strip's magenta = 
(74,0.8). The last magenta I dealt with was the Claria/Noritsu. It was almost 
neutral in terms of its Lab B also.

> 
> ... Complete control of Lab A & Lab B is the 
> goal. Though I am beginning to think it is only possible 
> using Photoshop curves.

If you have your gray (carbon) inks in K, M, C, and Y, you'll have a lot of 
trouble controlling the inkset with PS curves and the Epson driver. QTR would be 
much easier. Profile the carbon/gray inks first. Then add the toners -- starting 
with the built in curves. You can control the amounts with the ink limits.

Paul
www.PaulRoark.com 





      

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