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Thread: Measured output of flash Fresnel lights.

  1. #1

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    Measured output of flash Fresnel lights.

    I have been interested in learning about and using flash Fresnel lights (Norman FS 6 and FS 10) for some time. I need light for large format photography, but I don't use films slower than 100 ISO. Some users of plate processes are lighting with large electronic flash(4800WS) from a beauty dish.

    I know that a diffused and polarized Norman FS10 throws a very nice light many times brighter than a beauty dish, so I just made a rough measurement of output from the Norman at 2400WS, and from a Dynalite-converted Castor 10" Fresnel at 1000WS.

    With the FS10 at 10 ft. from the meter. Light set to flood 2400WS equaled F45 at 100 ISO sync at 1/60 sec.
    With the FS10 at 10 ft. from the meter. Light set to spot 2400WS equaled F64
    With the FS10 at 5 ft. from the meter. Light set to spot 2400WS equaled F90

    With the 10" Castor at 10 ft. from the meter. Light set to flood 1000WS equaled F22 at 100 ISO sync at 1/60 sec.
    With the Castor set to spot at 5 ft. from the meter at 1000WS equaled F45

    Looks like a flash Fresnel could be a practical as well as a classical way to light for those slow plates and films.Click image for larger version. 

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    Last edited by Neal Chaves; 21-Oct-2019 at 06:29.

  2. #2
    Peter De Smidt's Avatar
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    Re: Measured output of flash Fresnel lights.

    I have an 8" version for Speedotron, perhaps a modified Desisi? I think it has a 4800ws tube. I can take some measurements sometime soon.
    “You often feel tired, not because you've done too much, but because you've done too little of what sparks a light in you.”
    ― Alexander Den Heijer, Nothing you don't already know

  3. #3

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    Re: Measured output of flash Fresnel lights.

    Quote Originally Posted by Peter De Smidt View Post
    I have an 8" version for Speedotron, perhaps a modified Desisi? I think it has a 4800ws tube. I can take some measurements sometime soon.
    There is a current production Speedotron 10" DeSisit Fresnel conversion with a 4800 WS tube. It is priced at more than $3000. I tried to post a link but the Speedotron site is down today. Here are links to photographer Teddy Smith using the Speedotron
    https://photography-on-the.net/forum....php?t=1284940
    https://photography-on-the.net/forum....php?t=1184804

    Conversion to Dynalite has several practical advantages as well as considerable costs savings over the turn-key solutions from Norman, Speedotron and several even more costly brands. Many nice 10" Fresnels are now being surplussed off by the large film and TV studios as they convert to LED fixtures. Dynalite Road heads, including the new 2065 head which can support a fan-cooled 650W modeling lamp can be quickly mounted and dismounted to function inside the DeSisiti or Castor for up to 2400WS of flash. I have reworked a Norman LH2400 head to fit nicely into a converted Castor, however there is no room for the fan and model lights up to only 150W (plenty!) can be used.

  4. #4
    Tin Can's Avatar
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    Re: Measured output of flash Fresnel lights.

    sin eater

  5. #5

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    Re: Measured output of flash Fresnel lights.

    This topic has come up before, about how much UV has to be blocked before the speed of orthochromatic films and plates are affected. All glass will block some UV. Can the UV filtration coating of flash tubes, soft boxes, etc. have a significant affect on wet and dry plates?

  6. #6

    Re: Measured output of flash Fresnel lights.

    Quote Originally Posted by Neal Chaves View Post
    ... Can the UV filtration coating of flash tubes, soft boxes, etc. have a significant affect on wet and dry plates?
    Not according to my experimentation with wet plate. I compared Speedotron coated and uncoated tubes (206 heads with 4800ws each using a 16" reflector) on the same plate, and could not see a difference. This is not to say there is no difference, it just didn't amount to anything visible.

  7. #7

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    Re: Measured output of flash Fresnel lights.

    I didn't think so either, although I have never used wet or dry plates. I do intend to try some Ilford Ortho film soon.

  8. #8

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    Re: Measured output of flash Fresnel lights.

    I didn't think so either, although I have never used wet or dry plates. I do intend to try some Ilford Ortho film soon.

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