Plate Curves and Ink Optimization Help

[Chopper1]

Hello all,

Hoping for some advise, experiences and/or opinions. Any and all input will be appreciated.
General information:

•We have a one year old 40” 4/c Komori H-UV perfecting press. We are G7 certified.
•We do not linearize our plates, they are no more than 2% off target at the 50% as is.
•We have been using Fuji ColorPath to create plate curves with varying degrees of success.
•We use the G7 Form IO_v20155b 28x40 form for our press runs for creating plate curves.
•We measure the P2P charts printed on that press form printed at house densities.
•We then create generic plate curves for both coated and uncoated paper (generic meaning paper).

After the initial press run and a number of iterations (usually 2) we have a new set(s) of plate curve data which we apply to our workflow (Esko AE, IE).
The curves are applied as a strategy, the data measured from units 5-8 from the P2P chart is applied as compensation curves to both units 5-8 and units1-4.

The questions are as follows;

1) As we do iterations the overall appearence of the press sheet improves, but we notice that as we progress we are noticebly red in quarter and mid-tones. Why? ColorPath is supposed to achieve grey balance.

2) Are we expecting to much? Should we iterate only until we are “ballpark” and achieve the desired result on press? After a point, after many (4) iterations, we lose too much dot gain and control on press.
So obviously we do not use the last iteration. This is despite the “best” result on the test form.

3) Should we create a single generic plate curve first (meaning dot gain, averaged per unit) and then use
ColorPath just for optimizing the once generic curves?

4) We are looking at implementing ink optimization (currently testing different offerings). What is your
experience as far as true ink savings, ease of implementation, ease or improvement in printing and gray balance?

 

[gordo]

I can't speak to how Fuji ColorPath operates, however, the traditional method of building plate curves does not usually require any iterations - certainly not 2-4. Plates are not linearized first. Resulting plate curves may (or may not) require a slight adjustment to restore grey balance.

Ink optimization involves applying heavy GCR to images by reseparating incoming image files. It is very popular in web environments (cold and heatset) as a cost reduction strategy. Overall typical ink usage reduction of chromatic colors is about 15% - 35% with an increase (around 40%-60%) in usage of the less expensive Black ink. Reseparating incoming image files also normalizes/standardizes the wide variety of incoming files that newspapers and magazines typically receive and optimizes them for the press.

Ink savings strategies are not that popular in general commercial offset because ink cost is not such a large percentage of the job cost as it is with web (especially coldset - i.e. newspapers). If you don't know what your shop's ink costs are then, as a rough guide - about 2% of revenue spent on ink in a commercial print shop. So, if you're a $5 million dollar a year shop then you spend about $100K on ink. With heavy GCR you'll reduce that to about $65K

incoming image files are more consistent and already (typically inadvertently) separated appropriately for the sheetfed press so the need to standardize/normalize is not as great.

Another issue for the general commercial printer is that reseparating client files can shift liability, should presswork fail to meet expectations, from the print buyer to the printer ("my files were fine but you screwed them up by reseparating them")

Ink optimization puts a high demand on the integrity of the Black printer since it now makes up a much larger part of the image than before. This can be problematic on web presses since they typically use very cheap black ink. On a sheetfed press this can make flesh color and pastels appear grainy (many ink optimization apps let you specify at what point to start the GCR to minimize the issue).

Grey balance stability is enhanced since SID shifts of the chromatic colors won't impact final color as much. So, color consistency is improved. However, that stability reduces the ability of the press operator to shift color if the client wants to play at press.

Sometimes heavy GCR can introduce subject moiré that would not have appeared with the original separation.

 

[gordo]

I appreciate the response Gordo. We spend around $300,000 on ink annually and @ 15% (I'm told typical reduction in offset ink) it would be significant savings for us. Regarding Fuji ColorPath, it is web portal software that is used to measure P2P charts and create plate curve to iterate until a desired target (GRACol 2006 in our case) is achieved. The software then validates the measurement (once target is achieved) as meeting that standard. In reality it is creating plate curves (for each unit) and tweaking at each iteration until reaching the desired result. If there is a Fuji color/press guy that wants to explain it more thoroughly or straighten out any misunderstanding on my part, I would be grateful!

Gordo, I would be very extremely happy to get more advice offline if you are up to helping out.

You can contact me at pritchardgordon (at) gmail (dot) com