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Pete Raynell

New Arri high speed ballast settings

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Hi there, I have recently purchased some new Arri lamps with the new high speed ballasts, I'm interested if anyone can offer a little more insight into the high speed scan function, specifically the "Auto manual" and "Manual scan" settings.

 

When would you use these over Auto scan? And what is the difference between Auto Manual and Manual?

 

Also, I have not used these lamps recording over more than 500 fps yet, however Arri state they can be used up to 1000 fps and beyond.. Does anyone have any experience using these over 1000fps and how far is "Beyond"?

 

 

For those interested this is the only information Arri seem to provide -

 

The EB HS high speed ballast, allow HMI discharge lamps to be used for high speed recording up to 1,000 fps and beyond.

As the first ballast of its kind, the EB HS offer a new AutoScan feature that ensures optimum light and image quality with a minimum of effort. ARRI is now offering this popular AutoScan mode in the 9,000 W class with its new EB 6/9 HS AutoScan ballast. Users can select between fully automatic operations (AutoScan) and manual frequency control (Man), or combine manual frequency setting with automatic monitoring and adjustment (AutoMan).

Using the AutoScan mode requires no further interaction by an operator. After a two-stage scan the lamp frequency is selected and set by the ballast; all parameters are continuously monitored and adjusted automatically if required.

 

Thanks,

 

Pete.

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An issue arises from resonance that occurs when running some lamps arround 1000hz. The resonance destabilises the arc and affects the output of the lamp.

 

To solve this issue ARRI allows the output frequency to be adjusted to a frequency that avoids this resonance. They offer three options of adjustment.

 

Firstly Manual gives you total control of the frequency the head is run at. You first set you dimmer level, then adjust your frequency to achieve stability.

 

Auto-Manual gives you control of the frequency, but the electronics in the ballast provide additional correction if you do start to get resonance.

 

Auto-Scan does all the work for you.

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Thanks for the info Matthew,

 

I can't really see any reason to use the "Manual" or "Auto Manual" settings then if "Auto scan" does all the work.

 

The only situation I can think of is if perhaps flicker is present at high frame rates such as 1000fps in auto scan mode, then maybe you would use the manual feature to try and find a sweet spot and eliminate it? Even then I would assume this would be a very experimental process.

 

I'm still curious as to just how many FPS you can shoot with these new ballasts past 1000?

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