How you measure colour in pressroom?

[kermit]

Do you use Lab values with spectrophotometer or you just measure density with densitometer?

[30YearsandCounting]

We use both.  All of the older presses are managed using densitometers.  Hand held units that the pressmen manually check the values on the color bar on the sheet.  We have one newer press that has Heidelberg's Prinect Image Control.  It uses a spectrophotometer and automatically scans the entire sheet and measures the LAB values.  Much nicer... but MUCH more expensive.

[David]

like 30years, we have the Heidelberg Prinect and handhelds for color/lab/density checks whenever they feel like it.


(we also have spectros in Prep/Color so we can double check the pressroom's readings)

[30YearsandCounting]

(we also have spectros in Prep/Color so we can double check the pressroom's readings)

Forgot to mention that we do that as well.  (Not that there is ever any finger pointing when there is a problem.) 

[jezza]

Am I missing something here? How are the two measures comparable?

[David]

it's not that they're comparable, we just have the ability to do several different readings depending on what we plan on doing with it.

Like I use the spectro to get LAB values for recipe colors for the Approval, and I get check the press sheet to see how close we get (or how far off the pressroom is).
on occasion use density values for similar comparisons, depending on the project.
We also use the readings off the press to update /modify our ICC profiles, which we will then output test targets and take various readings to check the settings.

It's also, that some of these devices will go away as we retire older equipment and update to newer stuff.

[Sparky]

Grew up in the world of densitometers to get close and then the "customer " was usually around to make small "tweaks" here and there until the color was right, and if not then it was pulled off press and corrected, then re-stripped, new plate made, back to the pressroom and another pull for the customer. Everything was always approved by the pressroom supervisor or me, the prep supervisor. Once everyone was happy the sample sheet was signed off on and the job was run. Wish that was still practiced today.
My new boss hates color bars on his "perfect" Presstek 34DI press, so I don't even use them and have to judge everything by eye , and compare everything to Epson proofs they tell me don't match to anything, "...just make it look good..."

[30YearsandCounting]

My new boss hates color bars on his "perfect" Presstek 34DI press, so I don't even use them and have to judge everything by eye , and compare everything to Epson proofs they tell me don't match to anything, "...just make it look good..."

I just don't understand why a pressman would not want color bars.

[LoganBlade]

with a di I "think" that all the information for keys are determined by cip3 data. if machine is calibrated correctly file in will print as expected every time? Just my simple understanding of the di setup.

[Sparky]

with a DI I "think" that all the information for keys are determined by cip3 data. if machine is calibrated correctly file in will print as expected every time? Just my simple understanding of the di setup.

In a perfect world that's true, Logan, but with a 2 year old machine that has over 7 million impressions on it and the boss refuses to buy a new set of rollers, well you can guess the hell I go through trying to maintain any kind of correct color. He also says to our customers "The proof you see will not match the final results on press..." He even wants to go as far as put a disclaimer on the proof approval that says as much. 

When I get a chance to do roller pressure tests (each week I do a different unit so they all get done once a month) I can't even adjust the screws to tighten them any more and have to call a tech in to do the pressure settings. They keep telling me "these rollers are shot, you need to replace them..." but at about $6,600 for a set (sale price) the boss won't do it, and I'm forced to make do with what I have.

[Sparky]

My new boss hates color bars on his "perfect" Presstek 34DI press, so I don't even use them and have to judge everything by eye , and compare everything to Epson proofs they tell me don't match to anything, "...just make it look good..."

I just don't understand why a pressman would not want color bars.

I do, I do, desperately

[G_Town]

It's been my experience that pressman, particularly of the older cantankerous variety seem to not want any help when it comes to color. They are the lord and master of the printing press and be damned any type of technology that will assist them should it be ink key presets, or colorbars and auto scanners.

I've heard it said before what prepress does is a science what the pressroom does is art. (think of a painter holding his thumb in front of his painting). That crap needs to stop if we are ever to get to a place where predictable color is the norm rather than the exception.

We are embarking on a G7 journey and I hope to bejesus that management sticks to it like a starving dog  on a soup bone.

p.s. The above is no way meant to denigrate the majority of pressman who do a great job and should be commended for working closely with prepress to achieve the common goal of producing a quality product for the customer.

ugh I feel so dirty

[born2print]

We're excited about GraCol7 too, starting some tests in prepress, very well measured and evaluated tests, it's (but I hope not, for a change) gonna suck when the pressroom throws a few sheets on at 10pm and reports the next day "it's no good" with no bosses, no measurements, no data, no nothin.
This is sooooo illogical, they are the ones with so many variables, we hardly have any variables and DeltaEs on the proofers is around 1 or 2 nowadays. ARGH.