XMF Characterization Curve Creation

ritchis

New member
I just started working at a place that uses XMF v.6 and am trying to get acquainted with it. We've had some issues at press that make me want to look at the plate curves but we have literally no documentation. However, I'm seeing some things in the XMF interface that seem counterintuitive, if the people here are using it correctly. I've attached two screen captures. Do these look right? They're kinda backwards from every calibration system I've ever used, but the folks here swear that this is what Fuji set them up with. I would have expected the "Actual" to be the scan values from a raw, uncalibrated plate print. But before I rock the boat I thought I'd better see if Japanese engineers have fooled me yet again.
 

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  • Target.pdf
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minder

Member
Did you just switch to positive plates? looks like a plate profile is still set for negative number. We had the same issue, we use negative plates, but when we were testing the Kodak Sonora plates which are positive, we had to apply a curve the opposite to what we needed. Hope that helps
 

gordo

Well-known member
Could you explain what "target" and "actual" mean in this context? I'm used to building curves where the "target" is the desired press response and the "actual" is actual press response based on a calibrated, but not linearized, platesetter/plate combo.
 

ritchis

New member
I was hoping that someone here could explain it. Intuitively, I would expect "actual" to be the measurements from an unlinearized target print. In other words, when we ask for 40% without calibration, what do we actually get? Every calibration routine I've ever used has analyzed uncalibrated target measurements in order to calculate a curve to linearize. Not being familiar with XMF, I was guessing that the "Target" values are for those occasions when we would want to adjust linearized values (for additional gain, for example). But again, I recognize that different companies may put a different spin on these things. That's why I want the insight of some experienced XMF users.

These are for positive plates, but there was no recent switch.
 

gordo

Well-known member
I was hoping that someone here could explain it. Intuitively, I would expect "actual" to be the measurements from an unlinearized target print. In other words, when we ask for 40% without calibration, what do we actually get? Every calibration routine I've ever used has analyzed uncalibrated target measurements in order to calculate a curve to linearize. Not being familiar with XMF, I was guessing that the "Target" values are for those occasions when we would want to adjust linearized values (for additional gain, for example). But again, I recognize that different companies may put a different spin on these things. That's why I want the insight of some experienced XMF users.

These are for positive plates, but there was no recent switch.

OK, It's important to get the terminology correct otherwise confusion ensues.

So.

It doesn't matter what the dot/tone is on the plate as long as it's consistent.

It doesn't matter whether the plate is linear or not as long as it's consistent.

What matters is once the imaging is calibrated (exposure optimized for the plate to robust in terms of ink and non-ink area integrity) it will have a plate tone response which may or may not be linear. Linearity of the plate is not important.

The (probably non-linear but calibrated) consistent plate gets put on press and will deliver a certain tone response. That is normally what is called the "actual". I.e. I put this plate on press and this is the actual tone response I get when up to standard SIDs.

The "target" is what you actually want the tone response to be.

I.e. I ask for a 50% tone in my file and I get a 60% on press but what I want is a 68% on press.

The actual is 60% and the 68% is the target.

Calibration software then adjusts the tones on the plate to change the actual to the target.

It does not matter whether the plates are positive or negative.

Don't guess or assume as these are key terms. Unfortunately there is zero info on the Fuji website.
 

ritchis

New member
I understand that consistency is king and that, at the recording stage, it absolutely doesn't matter what the readings are. What's important is that they're repeatable. I just want someone to decipher these two screens from an XMF perspective.

Referring to the screen captures I posted, I can buy the idea that the entries for "Target" are a press target (When the file asks for 60%, please give us 64.8%), although the Target values seem a little arbitrary to me. I'd love confirmation of that from someone that actually uses XMF.

My other question is, for anyone that knows the XMF system, doesn't it seem strange on the "Actual" swatch that the recorded values and the "base" or "grid" values are identical? It seems to me that for that to be right, either that table is unnecessary or this particular platesetter is freakishly accurate.
 
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baggie

Member
Hi Ritchis
Your summary is correct. The intention is that the entered values for "Actual" are those that were measured from the printed result using the consistent (linear) plates. The values in "Target" represent what the desired result would be and would normally be taken from a defined standard e.g. G7 or ISO12647 here in Europe. In other words it is meant to work just as you would expect. It looks, in this case, as though the values have been fudged to give a desired result (a boost to the dot values) without actually going through the proper procedure of print and measurement. Probably not best practice.
 

Boneck

Member
We have a similar curve on our platesetter… while we are not spot on as you are for the actual… the Target values were measured compare to "film" jobs that had saturated mid-tones (dot gain). When our platesetter was put in… we targeted it to matching the tonal "gain" of a film printed job… with the platesetters being able to have linear plates… we wanted to be able to reproduce the jobs that we had already printed and made those values our targets… thus the "bump" in the mid tones for the platesetter.
 

cosmo

Well-known member
From what i can see, your target is a standard, ie iso 12467m gracol etc. Your actual is what you are reading, so you need to do an "Actual reading" and then put those values in, then xmf will + or - the values to get to your required standard. We still use xmf 3.xx, and once i set it and tweaked it a few times on the press its pretty much stayed perfect, dont under estimate xmfs power, its the best out there imo.
 

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