Rope Light Flicker Etc.

[Kyle Rogers]

I need to record in a location where the main lighting is from a rope light that flickers (supposedly with full-wave rectifiers). I know almost nothing about electricity, voltage, amps, watts, etc., but as far as I can tell the flicker is due to the alternating current that the rope light is getting from the outlet. Is it possible that there is something I can buy that converts the AC outlet power to DC necessary for the rope light, and that it's completely safe and I don't have to tear into the rope light?

Further details: I'd like to shoot at 24fps (technically 23.976); the flicker doesn't appear if I use a shutter speed of 1/30 or 1/60, but I get black bars that slowly move up at 1/50. Additionally, shooting at 24fps and using a shutter speed of either 1/30 or 1/60 makes everything look a little... off. 1/60 is probably the best, but it seems to give a bit of that Behind Enemy Lines/Saving Private Ryan/Rosencrantz and Guildenstern are Dead look. I've thought about doing 30fps, but I'd much prefer 24. I might be imagining this, but I think 24fps looks more filmic, and this is for a film... I recognize that since almost all screening and distribution methods are digital, the 30fps piece is probably irrelevant, but I'd really like to get to 24fps.

Probably irrelevant details: Camera is Sony a7sii, shooting at 4K 100MB/s, and this is the rope light: https://www.1000bulbs.com/product/20...DR-CW-146.html

[Pete Cofrancesco]

They sell flicker free drivers

LED Flickering In Video Recording SIRS-E - YouTube

Full frame dslrs like the A7s have a slow refresh rate and are more susceptible to this problem.

[Kyle Rogers]

Thanks! I know completely nothing about tech - the lights currently in place have a driver installed with them, I believe. Am I able to just cut the current lights at one of the cut marks and then use this driver, and if so, how would I install the driver?

[Gary Huff]

Originally Posted by Pete Cofrancesco

Full frame dslrs like the A7s have a slow refresh rate and are more susceptible to this problem.

The refresh rate on the A7S causes rolling shutter artifacts, not flickering. Flickering is directly related to shutter speed. I use 1/60 routinely, even at 24p, over this issue. No one will really notice much of a difference between 1/48 or 180 degrees vs 1/60, so it's not worth fretting over.

Occasionally i have dealt with fixtures that require a really odd shutter speed, such as 1/60.3. That's when having a camera that can give you such shutter speeds (usually named some variation of Clear Scan) comes in handy. My C300 Mark II/C200 combo does this, and so does the GH5. I can't remember if the Sony cameras have this feature.

[Pete Cofrancesco]

Gary you might be right but I’ve always noticed that the larger the sensor the more proned to this problem. I have 3 cameras:1/3, 1”and a APSC. The apsc dslr is always the worst despite the same frame rate. Similar thing happens when filming projector screens. But I agree wouldn’t hurt uping the frame rate but does the a7sII run at 60p.

Sorry Kyle I don’t know anything about these type of lights.

[Gary Huff]

Originally Posted by Pete Cofrancesco

I have 3 cameras:1/3, 1”and a APSC. The apsc dslr is always the worst despite the same frame rate.

It may seem that way unless you were filming the same light source with all three cameras at the same time and compared the footage and noticed the flicker more so. Plus, it's possible that your shutter speeds are different between the three cameras. I don't know what APS-C DSLR you have, but it's possible your 1/3 and 1" have the ability to do 1/48 and you're set to 1/50 on your APS-C camera.

But I agree wouldn’t hurt uping the frame rate but does the a7sII run at 60p.

This has nothing to do with your frame rate. It is solely in the realm of your shutter speed. You are more than welcome to record at 23.98 or 29.97 with a 1/60 shutter speed like I do.

[Pete Cofrancesco]

I get frame rate and shutter speed mixed up. But you're right shutter speed.

I'm saying for I've filmed events with all 3 cameras filming simultaneously with the same settings and the dsl was the worst followed by the 1" and the best was the 1/3". This also goes for venues with LED colored lights.

[Kyle Rogers]

So basically, it's not the 60hz and 1/60 issue as much as it is a rolling shutter issue... but if the lights were 60hz exactly, would that correct it? Or are the lights at exactly 60hz, and it's the rolling shutter that's causing the issue?

Basically what I'm getting from you is that something like this happens every 1/60 of a second:

Light turns on
Shutter opens
Camera scans x lines
Light turns off
Camera scans x lines
Light turns on
Camera scans x lines
Shutter closes



So if it's the rolling shutter that's the problem, is there any fix that doesn't involve a different camera or different lights? (Presumably a global shutter camera or a constant-power light source would work; based on what you're saying, I'm guessing this wouldn't be the right forum for figuring out how to alter the current lights so that they're on constantly.)

[Kyle Rogers]

Also, if the refresh rate is sped up, will the rolling shutter issue remain? My guess is that the refresh rate would somehow need to be connected to the speed of the camera scanning?

[Gary Huff]

The rolling shutter is not an issue. It can be that the lights are not at an even hertz, and without some kind of Clear Scan functionality where you can get, say, 60.40Hz, then you can’t fix it. However, Digital Anarchy’s Flicker Free plug-in works really well.