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Does anyone have any experience using arri 150s for stop motion animation? I thought it was my other lights but its actually the arri which produces this flicker and occasional shift in light.  I h…

Does anyone have any experience using arri 150s for stop motion animation? I thought it was my other lights but its actually the arri which produces this flicker and occasional shift in light. 
I have tried everything. shooting at 1 second, changing fuse and bulb, covering up the back of the light (which nearly put my studio on fire), and also taping the dimmer bit tight and nothing seems to work. Does anyone know what might be wrong? I'm using two layers of diffusion with them as well.
They are the dimmable ones and it's supposed to be continuous but it's not. Going a bit crazy with it so any advice would be massively appreciated!

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Comment by gustavo arteaga on March 16, 2021 at 10:25am

Hi. This may sound dumb but, have you tryed replacing the bulb? We use Arri 150s for stop-motion at Uni. They behave well with and without external dimmers. No flicker. The cheap Osram bulbs we use last a good while. Just before they die they begin to get brighter so there is a bit of warning. Anyway. Maybe worth trying changing the bulb if only to rule it out.

Comment by Jacob Lee on March 13, 2021 at 4:33am

Thanks everyone this has been incredibly helpful!

Comment by Simon Tytherleigh on March 12, 2021 at 5:51am

The Dedolights do convert to DC, and I did think the ballast would act to smooth out any fluctuations. As I said it may just have been because my unit was old. It is interesting that the Lowel tungsten lights work just fine, maybe they have some circuitry that smooths out the voltage fluctuations.

At any rate, it looks like the Arri needs to go. When buying new lights I would suggest LEDs, but bear in mind what I said about PWM dimmers etc.

Comment by Anthony Scott on March 12, 2021 at 5:40am

I am not an expert on lighting whatsoever, but I thought I'd put this out there, I shot a project at home with compact fluorescents a few years back (2013). I think my exposure was set at 2 seconds. I used an Auto Canon 35-70mm lens, (not a manual lens), the shot took 3 months to shoot, usually shooting for 4-5 hours per day in the morning starting at 9 am. I did not get any flicker, there wasn't a voltage regulator. It was also shot on the 2nd floor in a wood framed building and I had no set shift. I can't explain it! :) 

Comment by Jacob Lee on March 12, 2021 at 3:40am

Thanks so much both. StopmoNick I think you're right, im just going to ditch the Arri, it sounds way too expensive to sort out...

Simon that's interesting about the Dedolight - so they don't convert AC to DC then? I've got two Lowel tungsten lights, which I have with 55w osram bulbs, and they work absolutely perfectly. Do you think there's a similar tungsten light with the dedolights, or do you have to go LED to guarantee no flicker?

Comment by StopmoNick on March 12, 2021 at 2:03am

Jacob -

The double conversion UPS coverts the AC to DC, charges a battery, then draws on the battery and re-converts back to AC, at a couple of volts less.  That isolates it from any fluctuations in mains power.  So any AC light can plug into it, into normal sockets.  It's not a $100 UPS, it costs 10 or 15 times as much.  If the Arri light is simply responding to voltage changes, just like it would to a dimmer, that should fix it.  If the Arri is faulty, it won't help.

I set up a voltage meter in front of the camera to test the mains power.  I switched a big oven on and off to make the voltage drops happen when I wanted them to, and sure enough, when the needle dropped, the light was dimmer.  Voltage changes anyway, with factories and homes in the area switching things on and off, and is only consistently stable at around 1 AM to 4 AM.  Not my preferred animating time!  So I spent Aus $4500 on the  Eaton Powerware UPS, plus another $A500 for the electrician to wire it in so I could use the overhead lighting circuit I had already put in.  Expensive, but I had just built a studio and found it was useless for stop motion, so it had to be done.  A portable plug-in one, at 1500 VA, would be enough these days, with mostly lower power lights, if you do need to go this way.  Maybe just ditch the Arri?

Comment by Simon Tytherleigh on March 12, 2021 at 1:08am

Unfortunately I have experienced exactly the same issues with tungsten Dedolights. It may be that the ballast was old, but the lights work very well for live action fiulming, just not for stop motion. So I have reluctantly abandoned them. I did buy a similar spotlight, but LED, off eBay, and this is robust and works very nicely with lots of light. 

https://www.ebay.co.uk/itm/Compackt-5500-3200K-50W-LED-Spotlight-Co...

But I am also using homemade LED panels, constructed using high CRI LED strips and fast (10K) PWM dimmers. I have warm white, cool white and ice blue in the same panel so can adjust the colour temperature very precisely. I note that eBay show a kit on offer from China for exactly this sort of thing. There are also a lot of YouTube videos showing how to do it. DIY Perks is especially good.

The other thing I have been doing is buying high quality domestic LED bulbs and using them in PAR 16 cans. You need to go for the high CRI type as some domestic bulbs have poor colour. But this is a good solution for lower power stuff. I would not use domestic dimmers as I think these can introduce flicker.

A note on flicker. The PWM dimmers do actually switch the LED on and off, so a slow PWM will cause significant flicker for stop motion. But a 10K PWM flickers 10,000 times a second, so is too fast to introduce flicker. I have been using these at quite low brightness and there is no flicker.

Comment by Jacob Lee on March 9, 2021 at 11:13pm

I think you're definitely right. The lights im using are two lowel I lights, an led panel and  then the arri 150. It's only the arri 150 that is flickering. I think I have a choice between getting a new light or buying the double-conversion UPS as you said. I guess I have two questions.

would a dedolight DLH2 150w tungsten solve it as it changes AC to DC?

Could I plug in my arri to a double-conversion UPS as you say or is there some wiring that needs to happen? it has a uk mains plug. 

Thanks so much for your advice

Comment by StopmoNick on March 9, 2021 at 3:23pm

Haven't used the Arri lights, I use much cheaper lights usually sold for disco lighting.

 What are your other lights?  I got variations in brightness from my halogen/tungsten lights, caused by the AC mains power varying by a volt or two, but if I have a fluorescent light on for a soft ambient light as well, it does not respond to the small changes in voltage. So that means only some lights are going up and down, and others stay the same, but it is not the light being faulty.  Tungsten lights are dimmable because they do get dimmer when the voltage is reduced.  (Some modern LED and Fluoro lights use a different kind of dimmer.)  But if the others are also tungsten lights and plugged into the same power source, and they don't vary in brightness, it does look like the Arri light is at fault.   have a double-conversion UPS in my studio to smooth out the power for the lighting, which fixed my flicker. 

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