QTR-Quadtone RIP

In the ink setup tab, can someone give me a layperson's explanation of 
what the density and limit selections do? 

I assume they deal with how much ink is applied, but that's just an 
assumption. 

I'd like to try creating an all-black ink curve for my epson 2400 
(turning of cyan, yellow, and magenta inks), and it would be good to 
know what density/limits do before I start tweeking. 

Best, David. 

PS - I've read the PDF manual for QTR that downloads with installation. 
It gave me some, but not really enough info. on density, limits, 
linearization, etc. to really understand what I'm doing. Are there 
other sources of info. I can check out, especially for someone just 
starting out in using RIP software?

David,

On 7/18/07, David <dkfreed@...> wrote:
> In the ink setup tab, can someone give me a layperson's explanation of
> what the density and limit selections do?

Limit has to do with the quantity of ink used.  100 is max amount of ink.
50 would be 50%.  It's mainly an issue of how much ink the paper can absorb.
Density is for relative density of a lighter ink compared with a darker ink.

>
> I assume they deal with how much ink is applied, but that's just an
> assumption.
>
> I'd like to try creating an all-black ink curve for my epson 2400
> (turning of cyan, yellow, and magenta inks), and it would be good to
> know what density/limits do before I start tweeking.

The "warm" curves are all just K, LK, and LLK.  If you want to tweak I'd
start with some existing curves.

Roy

>
> Best, David.
>
> PS - I've read the PDF manual for QTR that downloads with installation.
> It gave me some, but not really enough info. on density, limits,
> linearization, etc. to really understand what I'm doing. Are there
> other sources of info. I can check out, especially for someone just
> starting out in using RIP software?
>
>
>
>
>
> Yahoo! Groups Links
>
>
>
>

Thanks again Roy. Good to know about the warm curves, since I didn't 
even look at them, assuming they wouldn't be all black inks. That's a 
good place to start. 

I'm printing to transparency sheets with the intent of using them to 
make photopolymer plates for etching. The usual photo aesthetic 
doesn't apply here, since what creates a good plate and print--with 
contrast and tonal range--is to start with an image where the curve 
has been compressed and flattened. And it also needs to be printed at 
720 DPI output. 

In short, it means a lot of experimenting and tweaking.

Best, David.  


--- In QuadtoneRIP@yahoogroups.com, "Roy Harrington" <roy@...> wrote:
> 
> Limit has to do with the quantity of ink used.  100 is max amount 
of ink.
> 50 would be 50%.  It's mainly an issue of how much ink the paper 
can absorb.
> Density is for relative density of a lighter ink compared with a 
darker ink.
> 
> 
> The "warm" curves are all just K, LK, and LLK.  If you want to 
tweak I'd

> start with some existing curves.
> 
> Roy

Roy, I understand your answer about limits being percent of ink. But
your response about density I still don't get:

"Density is for relative density of a lighter ink compared with a
darker ink." 

I have a specific purpose here: On my Epson R2400 I'm printing to
transparency film and want the range of tones to be created more by
"specs" of black ink and less by a continuous tone--so my print looks
more like a random pattern bitmapped image. That's part of the reason
I'm using 720 DPI. 

I use the transparencies to expose photopolymer film for creating
etching plates. What creates the tone in the print are the specs of
black, which translates to texture on the plate, which holds the ink.
The more, or denser, the dots the darker the tone. 

What's happening now (using one of the warm curves), is that I'm
getting blacks in my print, but the mid-tones and hightlights are
dropping out, and when I look at the transparency I see the darks are
made of dots and the midtones and highlights are more continuous
tone.--I want more "dots" in these areas. 

I'm considering, then, upping the limits (percent) for my black ink,
and lowering for the light and light-light black, but I don't really
understand how density works in the equation.

For example, if my light black ink was limit 50/density 30, what    
happens when I change density down to 15?       

Best, David.

David

Given what you state regarding needing dots in the transparency to
create texture on the plate, it seems to me that you want to be using
only black ink for your application. It's possible to create a QTR
curve using black only. Another possibility is to use BO printing with
the Epson driver using methods described by Clayton Jones (on the
Black and white the print list) - although I'm not sure the Epson
driver for the 2400 supports BO printing.

Tom Moore 

--- In QuadtoneRIP@yahoogroups.com, "David" <dkfreed@...> wrote:

...

> 
> I use the transparencies to expose photopolymer film for creating
> etching plates. What creates the tone in the print are the specs of
> black, which translates to texture on the plate, which holds the ink.
> The more, or denser, the dots the darker the tone. 
> 

...

> 
> Best, David.
>

Thanks Tom. I realize this is a fairly specific application and not
one that's very common. 

Even though I'm still not sure what density does, I did create a QTR
curve that upped K to 80% limit, halved the LK density and limit and
turned off the LLK. I'm happy to report that this got me closer to the
results I'm after--I got a print with more in the midtones the lights,
and darks were not so bunched up. 

I'll keep tweaking both my QTR curves (now I'm not so nervous about
upping the K) and curves applied to the images in Photoshop till I hit
 on what I need. 

Also, the R2400, fine printer that it is, does not allow K only
printing. The closest it has is an Advanced B/W mode, but it gives you
no control of the ink set and also this mode prints at a lot higher
output resolution than what I need (which is 720 DPI). So it looks
like QTR is the answer!

Best, d. 

PS -- and still wanting laypersons' explaination of density. I guess
I'm a bit dense myself here. 


--- In QuadtoneRIP@yahoogroups.com, "Tom Moore" <rtmlists8888@...> wrote:

>
> David
> 
> Given what you state regarding needing dots in the transparency to
> create texture on the plate, it seems to me that you want to be using
> only black ink for your application. It's possible to create a QTR
> curve using black only. Another possibility is to use BO printing with
> the Epson driver using methods described by Clayton Jones (on the
> Black and white the print list) - although I'm not sure the Epson
> driver for the 2400 supports BO printing.
> 
> Tom Moore