A few recent threads have gotten me thinking...

[Slammer]

...a thought, I am treating it well as it is in a strange place.
If as some posters tell, you need a plate curve and a press curve if you wish to have your processes under control. I for one like a one curve workflow but for now, just for the sake of argument that is neither here or there.
Up until now I have not come across a reliable method to measure process less plates without things getting really messy really fast, so I would assume that my CTP outputs by default a linear plate, i.e. 25% request is 25% on plate, 50% request is 50% on plate 75 is 75 etc. I would then determine the TVA and compensate accordingly with a press curve.
Still with me?
Good!
What if I don´t trust my CTP to output a linear plate, you know, old machine, laser on it´s last legs, poor thing should have been put out to pasture yonks ago. Or a new-ish machine, from Botchit and Scarper´s pre-loved CTP main street emporium. If I could get the service manuals, hook up a crystal ball or a oscilloscope and check if the machine´s tolerances are within the manufacturers recommended data, then in theory, at least, the CTP should output linear plates, or am I overthinking things?

Or under thinking things, not too sure now.

 

[Joe]

Maybe it is just ours but I've never seen a linear plate without a plate curve to get it there.

 

[buckeye]

I'm with Joe. That's the whole idea OF the plate curve - it makes it linear. Without a plate curve, our platesetter produces a 44% dot in the 50% area when using positive plates and it produces a 56% dot in the 50% area with a negative plate (process less).

 

[Slammer]

Maybe it is just ours but I've never seen a linear plate without a plate curve to get it there.

I do have a reference point, a customer using both processless plates and standard plates on a Trendsetter, when I measure the standard plates I get a linear plate output, 25% is 25% etc. From this I deduct that the processless plates are linear.

 

[Joe]

I do have a reference point, a customer using both processless plates and standard plates on a Trendsetter, when I measure the standard plates I get a linear plate output, 25% is 25% etc. From this I deduct that the processless plates are linear.

You should buy a lottery ticket. You are destined to win.

 

[gordo]

When you build a press curve - the curve that results in the tones you want to have on the press sheet - you do not need need to have the plate tone values.
You need the requested values - the tones in the file. You need the target values - the tone values that you want the press work to have, e.g. "a 50% tone request in the file should measure 68% on the press sheet." And you need the current tone result on the press - e.g. the 50% tone request in the file measures 74% on the press sheet. From that information a dot gain compensation curve is created, e.g. a 50% request in the file is remapped to a 43% request because a 43% request in the file results in the target 68% measured on the press sheet.
Measuring the plate is only needed for monitoring plate imaging consistency. Depending on the consistency of plate imaging this may or may not be an issue. Process free plate imaging tends to remove a major cause of plate imaging variation so consistency is increased and so the need to monitor plate imaging consistency is reduced.

 

[Slammer]

When you build a press curve - the curve that results in the tones you want to have on the press sheet - you do not need need to have the plate tone values.
You need the requested values - the tones in the file. You need the target values - the tone values that you want the press work to have, e.g. "a 50% tone request in the file should measure 68% on the press sheet." And you need the current tone result on the press - e.g. the 50% tone request in the file measures 74% on the press sheet. From that information a dot gain compensation curve is created, e.g. a 50% request in the file is remapped to a 43% request because a 43% request in the file results in the target 68% measured on the press sheet.
Measuring the plate is only needed for monitoring plate imaging consistency. Depending on the consistency of plate imaging this may or may not be an issue. Process free plate imaging tends to remove a major cause of plate imaging variation so consistency is increased and so the need to monitor plate imaging consistency is reduced.

That is what I was saying, but the question was not about the TVI on press and the requested dot on plate, the question I asked was that if I can exactly determine that the state of the CTP is within specs, can I assume that the plates it outputs are linear? Kind of like that ISO 9000-odd thing which basically boils down to the statement; "if the procedure is perfect then the finished product must logically also be regarded as perfect.

 

[Joe]

You can't assume anything. Output a plate with no curve and measure a calibration scale with a plate reader to see if it is linear.

 

[Slammer]

You can't assume anything. Output a plate with no curve and measure a calibration scale with a plate reader to see if it is linear.

I would love to but this hypothetical customer is running processless plates and you can´t measure those buggers, you can try to measure the plate on press after they have been washed and inked but that gets messy and the results are, well meh!

 

[buckeye]

Can't you wipe the plate scale with fountain solution before developing it on press? Which processor less plate are you using? I know some have more latent images than others. Fuji's has the lightest latent image, then Kodak, Agfa/Heidelberg and we just tested Presstek's Gem plate and it's latent image is hands down more visible than the others.

 

[Alois Senefelder]

Gentlemen,

Why are you not using ....... Fogra Digital Plate Wedge for checking the CtP Imaging Exposure ??????


Regards, Alois

 

[ChrisZ]

We do, but it is not enough for some type of plates.

 

[Alois Senefelder]

ChrisZ


Explain - why the Fogra CtP exposure control is only good for certain plates ????????????

 

[gordo]

ChrisZ


Explain - why the Fogra CtP exposure control is only good for certain plates ????????????

If your measuring device can't read/see the image on the plate then the control patches are of no use.

 

[Slammer]

ChrisZ


Explain - why the Fogra CtP exposure control is only good for certain plates ????????????

What Gordo said. So back to my original question... "can I assume that a procesless plate is linear if the CTP is within specs?

 

[Alois Senefelder]

Gentlemen - gentlemen !


Let some "common sense prevail" ---- the plate as been imaged, using a Lint Free wipe, swab the Ugra/Fogra control strip area with

1) F.S. or Aqueous Plate Devoloper or Plain Water or Plate Finisher.............. AND visually check via 12X Loupe


Regards, Alois

 

[Slammer]

Gentlemen - gentlemen !


Let some "common sense prevail" ---- the plate as been imaged, using a Lint Free wipe, swab the Ugra/Fogra control strip area with

1) F.S. or Aqueous Plate Devoloper or Plain Water or Plate Finisher.............. AND visually check via 12X Loupe


Regards, Alois

Tried that, methinks I could roughly recognise a Euclidian at 50%, round? Not to sure anybody could do that with precision. But let´s spin this hypothetical scenario a bit further, just for the sake of argument mind you. Customer would be a pharmaceutical printer and they demand a documentable readout for quality control.

 

[AmirKotti]

As soon as the machine runs and you make the linearization therefore the frame and correct in the plate. you remain the process calibration between the prepress flow and the printing machine depending on the paper you use ink to minimize fattening

 

[dabob]

Tried that, methinks I could roughly recognise a Euclidian at 50%, round? Not to sure anybody could do that with precision. But let´s spin this hypothetical scenario a bit further, just for the sake of argument mind you. Customer would be a pharmaceutical printer and they demand a documentable readout for quality control.

"Documentable Readout" are they specifically asking for a plate dot value? Could they be asking for a "final dot value" on the printed sheet, I believe that they would want the 2nd and wouldn't know what to do with the 1st since its value to the end product is only as a reference/starting point I would throw a 5 or 10% steps that you could measure would be good enough for them.

As far as the plate measurement goes . . . you have to know where you are to even start finding out how to get where you wanna be . . . .

 

[Slammer]

"Documentable Readout" are they specifically asking for a plate dot value? Could they be asking for a "final dot value" on the printed sheet, I believe that they would want the 2nd and wouldn't know what to do with the 1st since its value to the end product is only as a reference/starting point I would throw a 5 or 10% steps that you could measure would be good enough for them.

As far as the plate measurement goes . . . you have to know where you are to even start finding out how to get where you wanna be . . . .

Well this hypothetical customer is so far up his own central orifice that they demand a documented plate dot value and there is no way to do this on processless plates. So if I hook up a measuring tool for the laser once a month, say a Anritsu, and check that the output is constant and if the manufacturer of the CTP says that a plate will be linear at 1.21 Jiggawatts and I measure 1.21 Jiggawatts, give or take a Jiggawatt or two, (Remember, this is purely a thought experiment) then I can assume that the plate is linear.
The inability to measure a processless plate is a nagging little irritant, like a hang nail, in the grand scheme of things it is not that much of a big deal but at the end of the day it is part of the process that is not under your control.