Microfading Tester International Discussion Group

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  • 1.  LED-MFT

    Posted 03-04-2025 06:34
    Hello,
    I'd like to replace the white and blue LEDs in our MFT, which are about ten years old, with a more powerful white LED at least equivalent to the one used in the Fotonowy (this is because the fading time is around five times shorter in the Fotonowy) Does anyone have any experience or tips for a specific model (Thornlabs?)? Thanks. Bertrand




  • 2.  RE: LED-MFT

    Posted 03-05-2025 13:01
    Dear Bertrand

    I don't have specific experience with the Thorlabs units, but looking at the website and given that you're coupling directly to your supply fiber, I'd say your options for white are 

    MWWHF2 Warm White 4000 K
    MCWHF2 Cold White 6200 K

    Obvs, the warm white will be more similar to artificially lit gallery conditions, and the cool white will be more similar to (well filtered) north daylight through windows. Since you specify Thorlabs, I assume that you already have a driver, and the question would be whether the driver is compatible with the LED unit. 

    Given that you want high power, you'd ideally use these with a 400 or 550 um diameter patch cable, if that's going to be OK for your spot size.

    We use a Mightex FSS-0380-0780-000-SLC-MA04-MU which costs around $3,000 including the driver, which we find to be very stable (although there is about 30 secs instability when switching power levels). You can customize the LEDs used in this unit if you talk to the manufacturer. 

    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





  • 3.  RE: LED-MFT

    Posted 03-06-2025 05:17
    Dear JP, thank you very much for your detailed reply with the various options. The purchase of a Thorlabs module such as the MCWHF2 Cold White 6200 K, is without doubt the least expensive as we have the driver. I appreciate the information on the Mightex, it's a versatile enough device to suit a wide range of applications, at this stage I'll put it on the wish list. Best regards. Bertrand





    Original Message


  • 4.  RE: LED-MFT

    Posted 03-24-2025 01:06

    Hi, All,

    I am providing some comparison data between the measured color temperatures vs. the original targets.  There are some gaps between them, depending on the designed CCT of an LED: the higher the intended CCT, the larger the gap vs. the actually measured CCT.  The root-cause of this is uncertain, we could not rule out the possibility of the blue-shift yielded inside the optical fiber and/or the micro lens materials.   I have confirmed the reliability of the spectrophotometer I used. Different suppliers of LED-MFT might have different gap size, depending on the optical material installed in the system.  I hope the information could be useful for the LED-MFT community, at lease to verify the actual CCT when publish research results that are related to CCT of the light source.  Below is the data table in image:

    This is a data table showing the gaps of the intended CCT vs. measured


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    Henry Duan
    Senior Conservation Scientist
    National Archives and Records Administration
    College Park
    United States
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