Microfading Tester International Discussion Group

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  • 1.  Color temperatures for testing

    Posted 21 days ago

    I appreciate the MFT-IDG group for this discussion platform and the webinars.

    I have questions about setting color temperatures and using them. Are the tests conducted at a single-color temperature, or are they conducted at two or more different temperatures? Do the results differ? 



    ------------------------------
    Shiho Sasaki
    Conservator, Asian Paintings and Paper
    Asian Art Museum
    San Francisco
    United States
    ------------------------------


  • 2.  RE: Color temperatures for testing

    Posted 20 days ago
    Hi, Shiho,

    I am sharing my understanding here.  I think what's more important than CCT is the light profile that will be used for the final display, which is somewhat correlated to the CCT of the light source, but not always exactly.

    If the display will be using daylight through UV filtered windows, then the light profile of UV & NIR filtered Xe-MFT is the best simulation, which typically has a CCT around 5000K in my Xe-MFT (it still has a very small amount of UV and violet component).  Today's LED can achieve the same 5000K CCT, but if it is achieved through "blue pumped LED" technology, it is not exactly the same light profile, since it has zero UV and violet component but with a very strong blue emission at ~450-470nm. 

    If the final display will be using warm-white LED of CCT = 3000K or 2700K, then the light profile of a LED-MFT of the same CCT will be the exact fit.

    I hope the above helps!

    Henry Duan



    Original Message


  • 3.  RE: Color temperatures for testing

    Posted 19 days ago
    Dear Shiho

    Are you asking about the color temperature of the light source you're using for MFT,  or the color temperature used to calculate the dE* results? 

    Either way, yes, the color temperature makes a difference to the results. However, it does  not usually make a difference to the ordering of results. That is, for reasonably continuous spectrum sources, more light-sensitive materials  (in general) test as more light sensitive than less light-sensitive materials, regardless of color temperature.

    JP

    JP Brown (he/his)
    Senior Conservator
    Vice-Chair MFT-IDG

    t: +1 312 665 7879
    f: +1 312 665 7193

    Field Museum
    1400 S. DuSable Lake Shore Dr.
    Chicago, IL 60605



    Original Message


  • 4.  RE: Color temperatures for testing

    Posted 15 days ago

    Dear Henry and JP,


    Thank you very much for your replies. These are helpful so that I can suggest for our setting.

    The color temperature I asked for was for a fading test, not for a delta E calculation. Rendering the orders: I wonder whether we need to specify which CCT was used for a particular test, so that one can refer to or compare with theirs (for a particular object type). Or can the results be solely used for the tested object only, and not comparable with other objects because of the condition of the colors in the testing areas, or such? 


    Best,
    Shiho



    ------------------------------
    Shiho Sasaki
    Conservator, Asian Paintings and Paper
    Asian Art Museum
    San Francisco
    United States
    ------------------------------

    Original Message


  • 5.  RE: Color temperatures for testing

    Posted 15 days ago
    Dear Shiho

    It's not a bad idea to record the (C)CT of a test, assuming that you are using a source that has a reasonably close correspondence to an actual black body radiator. However, for some LED sources, it's not clear what the color temperature of the source means (e.g., an LED source with a CCT of 2700, and an incandescent bulb, have broadly similar color appearances, but somewhat different spectral power distributions). I guess one way around this would be specify the nearest CIE Illuminant.

    At the Field Museum, where we have a four channel LED source, we save the SPD of the source as part of the test data. 

    JP

    JP Brown (he/his)
    Senior Conservator
    Vice-Chair MFT-IDG

    t: +1 312 665 7879
    f: +1 312 665 7193

    Field Museum
    1400 S. DuSable Lake Shore Dr.
    Chicago, IL 60605





    Original Message


  • 6.  RE: Color temperatures for testing

    Posted 14 days ago
    Hi, Shiho,

    To report a MFT test result, I think reporting the type of light source used for the test is more important, Xe MFT with UV-IR band filter (in my case, the measured CCT is ~5000K), or LED MFT.  In the case of LED MFT, do mention the CCT spec of the LED used in the MFT, 2700K, 3000K, 400k or something else.  

    Hope the above would be helpful to you!

    Henry



    Original Message


  • 7.  RE: Color temperatures for testing

    Posted 14 days ago

    Thank you very much, JP and Henry, for taking the time to reply.

    All are useful and gave me food for thought.

    With warm regards,

    Shiho



    ------------------------------
    Shiho Sasaki
    Conservator, Asian Paintings and Paper
    Asian Art Museum
    San Francisco
    United States
    ------------------------------

    Original Message


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