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  • 1.  Instrumentation

    Posted 06-08-2019 04:54 PM
    Edited by Roger Breton 06-09-2019 12:12 PM
    This is not a question per se but a premilinary result of some interesting findings.

    My goal, in doing this research, is to evaluate the relative accuracy of popular instruments like those made by German and American manufacurers -- no Chinese instruments in sight yet.

    The basis of my comparison, so far, is a simple P2P51 target, printed with Huber inks on International Paper Everest SBS cardboard on a 7 color 40" KBA press. To my eye, this substrate exhibits very little, if any, optical brighteners. That is why I stuck with M0 measurements for this part of my study. M1 will follow later.

    I chose to measure all 300 patches of the P2P51 iby hand, in Spot mode, one little "square" at a time, patiently. I know :-)
    I made two sets of measurements, one using a Minolta FD-7 and one using an i1Pro2

    I consider the i1Pro2 a "mandatory" tool for anyone doing serious color management as it's so versatile and, for all intents and purposes, sufficiently accurate and repeatable for most professional color work. I mean that. Yet, it can never beat the convenience of a standalone instrument, for press work, G7 calibration, process control or general color work, like a Spectrodens or an eXact.

    So here goes. And I'm quite surprised by the results.
    On the basi of this data, if I had to do a G7 press calibration tomorrow and all I had was an FD-7, I would have confidence making all the ncessary press adjustments with my eyes blindfolded.

    Roger Breton G7 Expert

  • 2.  RE: Instrumentation

    Posted 06-09-2019 12:19 PM
      |   view attached
    I'd like to follow up with a PDF showing each instrument measurements.
    See attached.

    This PDF has a few layers, one for the name for the fourn process colors inks themselves which should be visible all the time.
    One layer presents i1pro2 screen captures.
    One layer presents FD-7 screen captures.

    Screen captures come from basICColor Catch v5 which allow reading the P2P51 using a variety of instruments.

    I chose to only show 100% Cyan, 100% Magenta, 100% Yellow and 100% Black, the standard four color process.
    I wanted to show both the CIE Lab values, Status T densities and Spectral curve.

    You can toggle On and Off the visibility of each layers to compare the numvers and the graphs.
    I find the documenbt speaks for itself.

    I find the numbers quite close to each other. Ideally, I should have thrown in some Delta E color difference metrics...

    Roger Breton G7 Expert


  • 3.  RE: Instrumentation

    Posted 06-09-2019 07:18 PM
      |   view attached
    More interesting stuff...

    This time, off the same printed P2P51 target, I ran a complete set of measurements using a second generation Spectrodens, which is a tungsten-based, M0, instrument. I could not get the measurements through basICColor Catch (only seems to support the WiFi version?) so the screen captures are a little bit different.

    See attached PDF which documents my findings.

    Thanks to Curve4, I was able to capture measurements off the Spectrodens in Spot mode -- easy as pie.

    I opened the FD-7 and Spectrodens measurement files, side by side, using BabelColor PatchTool v6, and proceeded to capture all the relevant information I could. To me, the most important information, of course, are the comparative CIE Lab values, which lead to Delta E color difference metrics (I included both DE76 and DE00), and the StatusT densities, the lingua franca of press operators around the world.

    I must say it is the first time I see two instruments measure so closely from each other, in M0 mode.
    Cyan, Magenta and Black are almost too close to be true. Yellow? I know that, historically, Techkon's Yellow readings are  systematically "lower" than everybody else's redings That has always been my experience. So I'm not surprised to see this difference turn out here also.

    Thank you for your interest.

    Roger Breton G7 Expert

  • 4.  RE: Instrumentation

    Posted 06-11-2019 07:53 PM
      |   view attached
    One last thing... As Steve Job woujld put it.

    Earlier, I compared the FD-7 to the i1Pro2 and the Spectrodens. The difference was very small, in my opinion.
    I still have to get to compare the FD-7 readings with the FD-9, in M0, on the basis of this P2P51 chart.

    Today, I completed comparing the FD-7 with an X-Rite 528.
    Again, the difference is rather small.

    I enclose a PDF for your perusal.

    Based on this analysis, I see no objection at all against using an FD-7 for graphic arts work and G7 calibration, in M0 mode.
    I wasn't expecting so much similarity between the FD-7 and the 528.

    I'm eager to test whether the FD-7 will still read as "close" as the i1pro2, the Spectrodens IV and the eXact in M1 mode...

    Roger Breton G7 Expert