Slow motion in gym - flicker?

F

firehawk

Veteran
Looking at shooting some scenes in a church gym built mid 1980s. Not actually a sporting event but an isolated spot in the gym. Nonetheless I cannot shut off the lights which I expect will flicker.
It would be 240 and/or 480 fps.
I can light the subjects with my flicker-free LED lights but there will still be light coming from the gym too.
Any ideas?
 
If you can't shut them off, I think your only choice is to try various shutter speeds and see which one eliminates the flicker the most, and/or use post-production software to try and remove any.

You could also try and avoid the lights (if possible) as the flicker should be most prominent if they are in the frame.

Can you get into the gym before the shoot and experiment?
 
firehawk said:
Looking at shooting some scenes in a church gym built mid 1980s. Not actually a sporting event but an isolated spot in the gym. Nonetheless I cannot shut off the lights which I expect will flicker.
It would be 240 and/or 480 fps.
I can light the subjects with my flicker-free LED lights but there will still be light coming from the gym too.
Any ideas?
Click to expand...
Hopefully you get lucky and everything works out.

As long as the flicker is behind the subjects, it could be used stylistically?
 
Thank you everyone.
Yeah I can fix it in post but if I do this little project I would have a TV set up to the camera for on-location playback so they can see it then and there.
Testing in advance doesn't look like an option.
The gym lights are way high up so I don't have any access to them.
Maybe positioning my subjects so as to reduce the amount of gym light on them so they have more of my light on them than gym light.
Can't think of a feasible way to block the light off since I'd likely have to set up some type of barrier above and around them.
Maybe playing with shutter speed might help a little.
 
You will almost certainly need to do something to the gym lights. Anything above about 120fps will flicker unless they have really new lighting. Blocking with a large fabric above will help, but generally reduce the amount of light from those fixtures and add a ton of your own light to reduce the overall problem.

Even playing with the shutter speed may not work and you will get a rolling color change, I've never been able to get things synced up well enough to eliminate this slowly circling color change from higher frame rates and discharge type lights in most gyms. That said I've never tried to add enough flicker free lighting to overcome this so you might get lucky with a stop above gym lights, but could take much more than that for all I know.

Hopefully this gym will be one of the really dark one that you can barely see to play ball in.
 
Large black fabric clipped with A clamps to c-stands above the subjects could help. At least then the flicker would just be in the background, and not on the faces / action.

Then you could use post to remove the flicker (I run into this issue so often I found the price of flicker free to be more than worth it). If you isolate it enough, you could even apply the filter just to the background part of the image using a duplicated layer and a mask, and maintain the integrity of the main subjects better.

It should be noted that the post tricks aren't perfect, they can make things slightly blurry or degraded. It's generally pretty good but depending on how critical your eye is for it, it won't be perfect. You can try it at home with a demo version to see.

Here are some black solids from Canvas Grip:

http://www.canvasgrip.com/c/Backdrops.html

You could also probably just rent one from a local spot.
 
You maybe could also rent one of those big party tents...one that has open sides. (Usually people from the company set them up for you.)

They are obviously for rain, but here one can be used for light(s).
 
Greg_E said:
Already said he can't turn them off.
Click to expand...

There is one thing here - when a client says 'you cant recce', 'we cannot get the location to flick a stwitch' then one has to be wary of the client - production of video is a team effort between client team and shoot team. Im noticing too many clients expect us to fix everything.

We are trying to make a video for the client after all. Trying to represent them, or thier goods/services in the best light. (pun intended)

As DP or producer part of the skill is to work with the people who say no and change thier answer to yes. Its much easier than hauling a huge lighting rig about.

Technical fix.. Make the ambient lights dark! Ie have ones own lights in close and on full power, if ones own package forces 1/64 ND in camera ths local lights will impact in only a minor way on the frame. One still gets flicker, but it is less impactful.

Ive done this in a factory before.
 
Thanks everyone.
So it looks like I will be doing this shoot in a couple weeks. I will be able to test maybe a couple hours the day of.

Normally on this type shoot I would light the subjects with my Dracast LED lights which are sufficient with a fast lens. But this time I'm thinking of blasting them with my Astra 6Xs or maybe bringing out my Lowel tungsten lights (500w or 750) to help compete with whatever gym light I can't keep off them. The cameras are FS700R so they have ND and I can stop down the lens.
Thoughts on that idea? I see morgan even suggested having my lights in close and on full power.
 
Those tungsten will flicker as they cool during the alternating current cycling. Minimum 1K and preferably 2K not to flicker.

Most LEDs won’t flicker if at 100%. You. Will. Need. A. Lot. Of. Light. Going from 24p to 48p requires doubling the light. Go to 96p and you double again (so 4X).
 
Mitch Gross said:
Those tungsten will flicker as they cool during the alternating current cycling. Minimum 1K and preferably 2K not to flicker.

Most LEDs won’t flicker if at 100%. You. Will. Need. A. Lot. Of. Light. Going from 24p to 48p requires doubling the light. Go to 96p and you double again (so 4X).
Click to expand...
Thanks Mitch. I won't bother with the tungsten lights then. I didn't know that
 
I've never noticed tungstens to flicker at full power, even at 250fps, most of this would have been with Lowel Omni lights. At what shutter speeds does this flicker happen on a 500 watt light and why doesn't a 1k or 2k flicker the same? Either way the filament is switching phase so it shouldn't matter unless the mass of the filament comes into play (1k often has thicker wire than a 500).
 
Good questions Greg. Thanks.
I have 500w omni, 500w rifa, 250w pro, and 750w tota Lowel tungsten lights.

I plan on shooting 240 and 480fps and will experiment at different shutter speeds
 
FWIW, I shot 120fps in a Jiu Jitsu studio a few months ago on the Fujifilm XT-3 and I tried everything discussed here. Same issue, I couldn't light the studio and owner wouldn't let me turn them off. This was for a documentary too, so one man band, tight schedule to get in, shoot for 20 minutes and get out. I tried messing with the shutter speed but to no avail. I also shot 4K 60p as my backup plan, which I will have to use as the 120 fps looks awful, really flickery, color cycling, etc. The 4K 60p looks fine so I will probably just use Twixtor or FCP's optical flow to slow down the 60p to get it closer to 120fps Doesn't help you much with 240 and 480fps though.

The proper way to do it is to shut off all practicals and light the whole scene with HMIs w flicker free ballasts or with flicker free LEDs. But not always possible with limited budget, crew and logistics.
 
Greg_E said:
I've never noticed tungstens to flicker at full power, even at 250fps, most of this would have been with Lowel Omni lights. At what shutter speeds does this flicker happen on a 500 watt light and why doesn't a 1k or 2k flicker the same? Either way the filament is switching phase so it shouldn't matter unless the mass of the filament comes into play (1k often has thicker wire than a 500).
Click to expand...

The lower wattage lights cool down faster/more during the "off cycle" than a higher wattage lamp(since they're burning hotter with larger filaments), so as it dims(more noticeably than the higher wattage lamps), it'll appear to flicker on camera. When I got my first camera capable of high frame rates(over 60), my F55, I was playing with it in my house and almost everything flickered, but f course we're talking about very low wattage tungsten lamps(prob 60 watts or less). Can't remember the exact frame rate I started to notice it, but it was way less than 250fps, since the F55 maxes out at 180 internally.
 
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