Imaging Working Group

  • 1.  Radiation sources for infrared photography

    Posted 11 days ago

    Hi Folks!

    We at the Walters are coming to the end of our supply of old-style incandescent bulbs that we have been using for near infrared photography with our multiband modified Z8 camera setup. I've found several vendors online from whom we could by the same or similar incandescent bulbs, but I am curious to know if anyone out there is using infrared LED sources for infrared photography. My understanding is that they tend to have rather spiky emission peaks, but perhaps there are arrays combining several that could be useful in the 700-1100 nm range? 

    If there is a workable infrared LED alternative, I would be interested in it from a sustainability perspective, as I imagine it would use less energy and last longer than old incandescents. 

    Would be very happy to hear from anyone with thoughts or experience with infrared LEDs. 

    Thanks!

    -Greg



    ------------------------------
    Gregory Bailey
    (he/him)
    Senior Objects Conservator
    The Walters Art Museum
    Baltimore MD
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  • 2.  RE: Radiation sources for infrared photography

    Posted 7 days ago
    Edited by Kyle Norris 7 days ago

    Hi Gregory,

    I don't know how much follow up you have had but this is an interesting topic starter. From what I have dug around and tried to find is that the LED output at this moment in time seems to top out at around 960nm, which could be just fine for modified camera setups. I would be interested to hear about an alternative because tungsten still gives the most upper end of the IR range needed (especially when we are using our Apollo camera for IR reflectography). Theres a company called dedolight california I was speaking with in the past about making the switch to LED and seems to offer some nice setups but never got them purchased or handled the product. Our Lowel TOTA tungsten lights are thankfully still functioning. If you do happen to hear of something that could work though I would love to chat some time about the possibilities. Happy to chat more if you want. Here is the link to their LED IR light:

    DLED7N-BI-IR 80w dedolight NEO Bi-Infrared 860-960nm Focusing Light – Dedolight California

    Good luck,

    Kyle



    ------------------------------
    Kyle Norris
    Graduate Fellow (Class of 2026)
    Conservation Center of the Institute of Fine Arts, NYU
    Trenton
    United States
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    Original Message


  • 3.  RE: Radiation sources for infrared photography

    Posted 7 days ago
      |   view attached
    Hi Gregory and Kyle

    I recently borrowed a Broncolor Scope D50/UV/IR light dome which we used with our modified Hasselblad H6D camera (silicon sensor with hot mirror removed and replaced with clear glass).
    The UV radiation on this specific piece of kit was more visible violet than UV, making it fairly useless for UV induced visible fluorescence. This was however my first time using an LED radiation source for capturing reflected (near) infrared using a silicon sensor camera and I found the IR LED's very impressive. We got some beautiful images without needing any filters over the camera lens. Exposure times were fairly short, focusing in live view was easy, no need for filtration, very easy.
    I took spectral power measurements of all three light sources in the dome; I'm attaching the IR measurement. It peaks at 943nm, with useable output between 830nm to 1000nm.
    This maps very closely to the spectral response of a silicon sensor. All this is to say I was impressed with the IR LED output.

    If you were planning on using a camera with more short wavelength infrared sensitivity, for example using an Apollo with an InGaAs sensor, then there are some 'SWIR LEDs' but my understanding is that these are still not as efficient nor have a spectral quality as good as thermal emitters, e.g. tungsten halogen, xenon arc...
    I'm very interested if anyone has any experience using SWIR LED's?

    All the best
    Andrew


    Andrew Bruce
    Senior Photographer
    The National Gallery

    M: 07766 620308
    T:  020 7747 2544




    Attachment(s)

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    m000527-081840_BroncolorScope-IR_A.rtf   2.06 MB 1 version
    Original Message


  • 4.  RE: Radiation sources for infrared photography

    Posted 6 days ago

    Hi Gregory,

    Phase One have a set of narrowband LED panels that include three near-IR channels - 730nm, 850nm and 940nm. Although they were primarily designed to work with Phase One's fully automated multispectral imaging system, they also include manual control, so you can turn each waveband on and off manually. There are 16 individual wavebands from 365nm to 940nm, plus a white light for regular RGB capture.

    Regarding Andrew Bruce's comment about UV in the Bron light dome, this will be a 'feature' of any LED based UV light source, as the LEDs themselves fluoresce from their own UV illumination, so they will always include quite a substantial amount of visible light as well, which does render them near to useless for capturing UV induced visible luminescence due to the inteference from the visible fluorescence from the light source. Adding a UG11 filter to the light will alleviate the problem, but these are only available in limited sizes so more often than not cannot be used. The same problem exists with the Phase One panels.

    I hope this helps.

    Best regards,

    Eric



    ------------------------------
    Eric Joakim
    VP Sales, Heritage
    Phase One
    Steyning
    United Kingdom
    ------------------------------

    Original Message


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