Brian Doran

Is there any chance it was the Licht- Technik Bag-O-Light? https://www.licht-technik.com/en/produkte/bag-o-light/

Just chiming in to say that the ballast in the photo is from 1995, about 26 years old. The last two digits on ARRI ballasts represent the year of manufacturing.

The lack of dimming is the only limitation to consider when using the S360s in high-speed mode. If you don't need the full beam spread, it might also be a good opportunity to use an intensifier on that head, I'm surprised they're not used more.

2 hours ago, Guy Holt said:

Not really supposed to market products on these boards.  Contact me off list through message or at rentals@screenlightandgrip.com for details.

Guy Holt, Gaffer, ScreenLight & Grip, Lighting  Rental & Sales in Boston

Sure thing, I'll send you an email tomorrow morning.

I seems like the only online traces of Shock Stop are on your blog, Guy. Do you know who might carry them for sale or rental? 

I'm not sure if this is what you're asking, but the list of gels programmed into the Skypanel, and methods for achieving them with XY, HSI, and RGBW, are available on ARRI's website. 

 https://www.arri.com/resource/blob/65960/7ad47c8a0279cd8084ee697b067f408e/arri-skypanel-gel-conversion-charts-data.zip The .zip file contains conversion charts for 3200K and 5600K, 8 and 16 bit.

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.

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, and this might not be represented in the lumen measurement. Let's say that five different fixtures are using the same LED engine made by Osram, well all five might list the same lumen value suppled by Osram, but this does not factor in the fixtures optical loss, reflector efficiency, etc.

So, I like foot-candles and lux. These units measure the number of lumens falling over a 1 square foot or 1 square meter area. Instead of measuring just the light source in an integrating sphere like in this photo, foot-candles and lux are measured as the light falls upon a surface at various distances from the fixture. Because of this, we are able to factor in optical efficiencies that might separate two fixtures with the same OEM light engine. Most foot-candle/lux charts will also show the beam angle, illuminance, beam diameter, distance relationship. This has the benefit of telling you how large of a space the fixture can illuminate to X level at Y distance when at whatever variable focal length, if applicable. Here is an example of an illuminance photometric chart.

Comparing lumens reminds me a bit of comparing the expected lifetime of LED engines. There are only a handful of LED manufacturers in the world, and our tiny little industry mostly buys from that same handful. It's the LED OEM that calculates the commonly referenced LED lifetime "L70" metric, which measures how many hours an LED engine can run before efficiency drops to 70%. That's all good and well, and it speaks to the quality of LEDs that the lighting fixture uses, but it is not analogous to the fixture's expected lifetime. When you see a streetlight flickering, it's because of an issue with the LED driver or power supply, not the LEDs themselves. The same is true in our industry, the electronics will likely fail before the L70 time is reached.

This is long winded. Like Phil said, you'll probably just get used to thinking of LED, tungsten, and HMI as three different beasts and have a general sense of the different degrees of lumen-to-watt efficiency between them. Just make to sure to double-check the photometric sheets when marketing material claims that X LED fixture is as bright as Y HMI fixture. HMI is still the brightest-per-watt, and I just don't know where some of these marketing comparisons come from...

Is the buzzing constant, or does the head buzz briefly and then go quiet, failing to strike the lamp? 

14 hours ago, Ed Conley said:

maybe their claim is using two batteries.

 

 

Yeah, it looks like they specify two 14.4v V-mount batteries. 

On 8/24/2020 at 9:04 PM, Craig Ryan said:

Good for you to test photometrics.  In my experience, most gaffers and DPs will call a lamp based on years of experience rather than actually metering lights, and thats all well and fine, but its great to have some back-pocket stats.

In general, it's probably best to do your own testing obviously.  Just make notes of the lamps you like to use, and that way you'll have it for future reference.  If you have a handle on the smaller lamps you like to use often, then it gets easier to "scale up" when the shows and shots get larger.  In general, for instance, the Mole and Arri fresnel lamps scale up as you would expect photometrically, same with Arri M Series HMI.  But, always test!  DP's (and other gaffers) never believe me when I tell them how much an M18 puts out in Full Spot.  If I had a nickel...

Like others have noted, inspect the lamps optics, and make sure everything is clean.  And the bulb, of course.  With tungsten, remember that the lamp needs it's rated voltage to perform optimally both in terms of output, and color temperature.  Meter the line before you test, and if possible, while under load and see how much the voltage takes a hit.  If the voltage running through the filament is less than the rated voltage, you won't see optimum results.  LED and HMI are obviously not the same, as they have power regulators.   

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 much extra voltage is needed to overcome the line-loss. helps keep things predictable.

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-Planckian sources like gelled lights or fluorescents.

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 different, please don't hesitate to correct me.

As for sourcing lamps, I find them to be rare enough that lamp failure is often reason to scrap the entire fixture. If anyone has a source, please let me know!

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. 

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.

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.

29 minutes ago, James Compton said:

No. I am not using the terms hard and soft in relation to shadow patterns. Characteristics like falloff and it's behavior upon striking a surface are part of what I'm referring to.

Are you referring to the rate of falloff here? 

2 minutes ago, Andy Jarosz said:

I weirdly understand what you're saying here. However, I would be very hesitant before bringing this up in a professional context, if for no other reason than it will cause confusion.

The reason is not because the light is actually softer, it's because the longer wavelengths are more visible to the eye and so it's just easier to see the harshness of the bluer lights. Additionally, bluer lights activate our photopic vision which makes that harshness even crisper.

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.

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 about color, it can be greatly informed by our memories and feelings. One might observe an orange to be of a greater saturation if that is what they remember as a child, etc. Balancing this real and justified emotional interpretation of light/color with the technical aspects is a challenge that the DP, LD, or gaffer must face.

As someone on the manufacturing side, I appreciate that the artistry of light may take on a different vocabulary and way of thinking. However, we work to create tools that best suite your needs, so maintaining a dialogue and getting input from the artist is essential if we want to create something useful. Sometimes we may need to take a step back and consider what we should do because it is useful, vs. what we can do because it is possible. At the end of the day, we are creating tools, and we must use objective methods and terminology if we want repeatable results and quantifiable goals. I'm not saying that we don't want to hear the artistic terminology, but if there are certain things that you like or dislike, digging into the technical language will help make our dialogue much more effective. 

When you say soft, perhaps there is an emotional context motivated by color or even the flickering that brings about memories of sitting around the campfire. When the R&D team designing a fixture says soft, they are referring to a diffuse source vs. a specular one. At the end of the day, our lighting instruments have to be described in purely technical terms for the sake of specifying and manufacturing; The further that you the artist can bring the conversation into the technical realm, the better the chances are that we can move the technology in a direction that suites your needs.

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.

That is not a light, it is an ultrasonic distance measuring device for the 1st AC. It's a bit like echolocation for bats.

Not a book, but I'm quite a fan of Luke Seerveld's YouTube channel, Meet the Gaffer. He does short vlogs of various lighting setups, explaining the function of each instrument. It's a bit of a living light plot. There are also episodes dedicated to miscellaneous tips and tricks. Great stuff.

I don't know the inner working of those regulated 48V DC batteries, but I don't suspect that a step-up transformer is utilized, as they're rather heavy, expensive, and are not regulated. The two batteries are likely run in series to combine their voltage, and then regulated through a boost and buck DC-DC converter. Doesn't really answer your question, but I couldn't help it. 

As for running an 800W HMI off of battery, the necessary warm-up time for an HMI might really chew into any operating time that the battery could supply. Short of buying or renting a voltstack, I don't know. If someone has a recommendation, I would also love to hear about it!

The standard ARRI 2.5/4K ballast with ALF draws between 37A and 52A at 90-125V. For information, the manual is available online, here.

Paging Guy Holt!