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How do I pick my refresh rate?

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Tim Weaver:
So many new fixtures come with the choice of refresh rate so they won't flash on TV, but I have no idea what to choose or why. Is there a reason why I wouldn't just max it out at 25k? Or is that hard on the equipment?

Is 1200 good if you are shooting at 120FPS? I have no idea.....


Can anyone here explain this?

Brian Jojade:
The shutter speed that is being used for video also needs to be taken into consideration when determining what would be the best frequency to set your lights at.

When you end up with a mismatch of the number of light on off cycles with the duration of the frame, it can result in an apparent difference in the amount of light.  As you get to higher light frequencies in relation to the frequency of the frame, it's going to be less noticeable if you're a cycle or two different, but when they get closer together it's much more pronounced.

Tim Weaver:

--- Quote from: Brian Jojade on November 13, 2023, 05:45:46 PM ---The shutter speed that is being used for video also needs to be taken into consideration when determining what would be the best frequency to set your lights at.

When you end up with a mismatch of the number of light on off cycles with the duration of the frame, it can result in an apparent difference in the amount of light.  As you get to higher light frequencies in relation to the frequency of the frame, it's going to be less noticeable if you're a cycle or two different, but when they get closer together it's much more pronounced.

--- End quote ---

I understand why it is. I don't understand why to pick 1200hz vs 4000hz vs 25,000hz. Why not just go max refresh rate at 25,000 which seems to be the highest most fixtures go to. Does 25k refresh lead to a shorter lifespan? Dimmer output?

Do I have to stick to some multiple of shutter speed and the rest is just a guess?

There has to be some theory beihnd this....

Brian Jojade:
Yes, a multiple of shutter speed is what you are looking for.

Rob Timmerman:

--- Quote from: Tim Weaver on November 13, 2023, 04:58:49 PM ---So many new fixtures come with the choice of refresh rate so they won't flash on TV, but I have no idea what to choose or why. Is there a reason why I wouldn't just max it out at 25k? Or is that hard on the equipment?

Is 1200 good if you are shooting at 120FPS? I have no idea.....


Can anyone here explain this?

--- End quote ---

Higher refresh rates typically come at the expense of lower dimming levels.  So for applications where video is involved (where flicker is a concern, but you likely need a fair amount of light), use higher refresh rates.  And for theatrical applications where you want extended dimming performance but don't need to worry about camera flicker, choose lower refresh rates.

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