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Magnetic ballasts with RED?

R

Ronnie Wenngren

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I wonder if I can use 50hz magnetic HMI ballasts with the RED One at 24 fps?
I live in Sweden and we have 50hz.
I have Arrisun 4/2,5k:s and Arri Compact 2,5:s available but are not sure if that works. I hope anyone of you can help me.
Thanks,
/Ronnie
 
Original choice... Don't use Magnetic ballasts (unless you have no choice).,,
Flicker....
 
You should have no problems as long as you follow all the same rules that apply to film. There have been reports of issues, however I have never experienced any problems after tons of Mag ballast HMI shooting, including off speed stuff. I attribute any issues to bad power, bad ballasts, or old leads.

Cheers,

Nick
 
Actually, a magnetic ballast will work just fine with a RED at 24 fps. The shutter speed is a crucial variable, however. See this thread here on REDUser:

http://www.reduser.net/forum/showthread.php?t=18926

However, I only use electronic ballasts. . . just to be sure. . . and to have more flexibility.

Stephen
 
i've used magnetic ballasts @23.98 & 1/48 with no problem. had to experiment a bit with anything overcranked.
 
I got burned with a visible rolling bar on some shots. 23.98fps 1/48th magnetic ballast in California (60 hz). Mains power, ballasts sent to LTM tested ok, stage power tested ok. Next, I re-created the rolling bar at the grip / electric rental house, with the same ballasts plus other ballasts.

Shoot your own tests and decide if it's an issue for your specific project.

To test shoot a grey card at 1/60th (or 1/50th if 50hz) and 1/48th. Compare the shots in post, you will see a rolling bar in the 1/48th clips.

More here.
http://reduser.net/forum/showthread.php?t=27993
 
Thanks for fantastic info. I live in Sweden and we have 50hz. Anyone in Europe having this issue? 24fps and 50hz magnetic ballasts?
 
david_winters said:
I got burned with a visible rolling bar on some shots. 23.98fps 1/48th magnetic ballast in California (60 hz). Mains power, ballasts sent to LTM tested ok, stage power tested ok. Next, I re-created the rolling bar at the grip / electric rental house, with the same ballasts plus other ballasts.
Click to expand...
Like you David, I'm not convinced that all film safe speeds carry over to the Red - probably due to the rolling shutter (lol, just checked my post and realised I'd accidentally typed "rolling shitter"! How apt...).

I'm not convinced the half-frame safe speeds (e.g. 1/48 in 60Hz, 1/20 in 50Hz, etc) are safe on the R1 - did you try 1/60th? That should definitely be fine.

I had problems with rolling exposure bars in South America whilst shooting "safe" speeds - moved to 1/60th and problem solved...

Cheers,
Dom.
 
1/50th should work just fine with 50 hz ballasts. 1/100th or 1/25th will work too

Here in California we have to set Shutter at 1/60th to use Magnetic Ballasts. Or we can use 1/40th. Your shutter must match frequency
 
I have never had a problem identifying light sources in which I am getting "roll" on set and dialing it out then and there.

Here in the USA 90% of the time a 144˚ shutter (1/60th), (just like film) will knock out flicker or "roll" in a light source.
 
J. Eric Camp said:
I have never had a problem identifying light sources in which I am getting "roll" on set and dialing it out then and there.

Here in the USA 90% of the time a 144˚ shutter (1/60th), (just like film) will knock out flicker or "roll" in a light source.
Click to expand...

100% true.
 
Indeed - the only point I was trying to make is that film safe speeds are not necessarily safe on the R1 (or any RS digital camcorder) as a previous poster stated...

Cheers!
Dom.
 
I use magnetic ballasts often with no problems. If you are worried buy a flicker meter from Arri.
 
It's a meter that will tell you if you can expect any flicker from your HMI lighting. They are about £399.00 from Arri, really useful if you are hiring lamps or have a number of lamps on the go and need to find out which on is not firing correctly. Works a little bit like a timing light for setting the timing on a car.
 
Thanks for important info. So here in Sweden may my safe speed be 1/60 at 24 fps? 1/60 may be safer than 1/48 - am I right?
I shall definitely look for a Flicker Meter, but didn´t find a seller via google.
Are Arri selling it, and it´s made by another company? I searched on arri.de and arri.uk but found no info.
I would appreciate info about a seller - if anyone know where?
Thanks,
/Ronnie
 
B&S sell one, but i would call Arri, they will sell you one. On the latest Arri price list they come in at about £349.00

http://www.thedopshop.com/product_info.php?products_id=36

speak to arri before buying this one here though make sure it has all the facilities you need. Good luck. :thumbsup:
 
Thanks for all important answers. Do anyone have a complete list of safe shutterspeeds with magnetic ballasts?
I have planned to shoot both 24 and 25fps in 4K and 50 and 60fps in 3K.
/Ronnie
 
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