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Brian Doran

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About Brian Doran

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  • Occupation
    Industry Rep
  • Location
    New York
  • Specialties
    ARRI Lighting Technician

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  1. Here's a simple inverse square calculator that I found. That should take care of the illuminance part of the equation. The other area of interest might be the illumination area based on distance and beam angle. Here's a beam angle calculator I found. Maybe there's an app that combines these two, not sure.
  2. I'm a big proponent of comparing fixtures based on illuminance values such as foot-candles and lux, rather than luminance values given in lumens. Lumens represent the total amount of light produced by the source, be it the tungsten bulb, the HMI lamp, or the LED engine. The problem with this is that it does not account for the beam angle, so it does not speak to how wide a source is. It is also my understanding that the lumen measurements are often made independent of the fixture that the light source is installed in. As Phil mentioned, light loss in optical elements is an important factor, an
  3. Is the buzzing constant, or does the head buzz briefly and then go quiet, failing to strike the lamp?
  4. Yeah, it looks like they specify two 14.4v V-mount batteries.
  5. Absolutely agree in regards to testing and being aware of line-loss for tungsten loads. I just want to add that although electronic ballasts can regulate the mains voltage and their output voltage, you can still incur line-loss across your run of header cable. Trying to use a single 100' run instead of two 50's, metering out your header to find any high resistance wires, and keeping clean contacts can all help keep resistance and thus line-loss down. The newer ARRI ballasts now use CCL (compensation for cable loss) circuitry, wherein a feedback circuit in the head is telling the ballast how mu
  6. Why not just use the TM30-18 Rf scores? With 100 color samples and a very intuitive graphic showing color gamut as well as shift, I think it's pretty hard to beat. It is based on the standard human observer, much like CRI, which can be an issue, but it certainly gives us more information with more data points and is thus harder to cheat. As far as I know, TLCI is based on CCD sensors, so it might not be an accurate predictor of CMOS sensor characteristics. SSI is the only one of the three with a real advantage, being that one can easily change the reference source if they want to match non-Pla
  7. If it's anything like the old ARRISUN 12, then you cannot use the modern G38 single-ended HMI lamps, no. The sealed-PAR lamp had its own reflector, so our old ARRISUN did not have or need one. Running a lamp without this built-in reflector would likely cause overheating and damage to the fixture, as much more heat would be absorbed by the inner baffle than was planned in the design. More troubling, is the lack of UV filtering glass on the fixture, again due to the sealed-PAR's inclusion of UV filtering. This is all based on my experience with the old ARRI heads, if the Desisti heads were diffe
  8. This is just my gut feeling, but wouldn't having a focusing lens on each LED cause multiple shadow issues? A diffusion plane is really helpful for homogenizing the multiple light sources into "one" source.
  9. That is a magnetic ballast. Like Phil said, you will have to be sure to synchronize with your camera to avoid flickering, and will not be able to dim the fixture, etc.
  10. That head hasn't been manufactured in 10 years or so, if memory serves. How does the reflector look? A bit of burnt-in dust and dirt over the years can easily decrease intensity by 20%. Though that wouldn't account for the increase you measure in spot. Perhaps the reflector has become misshapen.
  11. Are you referring to the rate of falloff here?
  12. I'm not sure that this logic holds up. Peak photopic sensitivity is defined as being 555nm, which is a green color. Check out this luminous efficacy chart. Maybe I'm misreading, but it also feels like you are referring to blue light as being longer in wavelength, while the inverse is true. If anything, our scotopic vision is more sensitive to blue light than our photopic. Please let me know if I'm misinterpreting your post.
  13. It seems to me that there is a disconnect between the terms used to describe the emotional evocation of different sources, and the technical terms used by researchers. I could imagine feeling a soft, intimate emotional response to fire light, and this response would be taking place in between my eye's observation and my brain processing that information. And that is not to say that it is invalid or that my brain tricking me, photometry is the study of how the human eye perceives light, and that eye/observer is just as important as the photons of light. That's one of the interesting things abou
  14. Not a standalone library, but the Illumination Engineering Society does have a photometric .IES file extension named for them. I've used a free program called IESViewer for these files. .LDT are also used, but I haven't played around with those at all. ARRI provides both file types for their current fixtures, and I believe ETC does as well. Not the prettiest UI, but it works.
  15. That is not a light, it is an ultrasonic distance measuring device for the 1st AC. It's a bit like echolocation for bats.
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