Strobe suggestion? at DVinfo.net

Marco Leavitt · December 25th, 2003, 04:26 PM

Anyone use a strobe to sync their sound? I want to get rid of the slateperson. You can never read what's written on the slate anyway, and we don't really have an extra person to clap it. Can anyone recommend a strobe?

Charles Papert · December 25th, 2003, 09:14 PM

I'm not really clear on this, Marco. What kind of strobe--a photo flash? Most strobes are pretty quiet, so you'd have to get the mike awfully close. I'm not really clear on what you are planning.

As far as not being able to read what's on the slate--umm--have someone write more legibly???! Seriously, it can really help to have a visual notation of scene and take for the edit. But that's a separate issue than the sync sound mark(I'm assuming you are rolling a separate DAT or something?)

The simplest way with no additional personnel to get a sync mark on both picture and sound is to have the actor clap his hands on camera. If he is way offscreen at the beginning of the shot, just have him do it at the end (i.e. tail slate).

Marco Leavitt · December 26th, 2003, 09:29 AM

I'm hoping someone makes a strobe that emits a beep when it flashes. I've seen this in movies about making movies anyway. Didn't they use one in "Living in Oblivion"? Anyway, I know it seems pathetic, but at our level, I don't feel I can really trust anyone to write on the friggin slate. Bad information is worse than no information at all. They never seem to do it right and I'm sick of it. Every time the wrong scene number or date gets written down it creates a huge problem in post. Also, when they clap the slate they never seem to stand in the right place so that it's in focus. Yeah, I've thought about having an actor just clap, but I'm worried it will take them out of character and they're whiny enough as it is. If I sound annoyed, I am. We're recording to minidisc, so I figure if I just make sure to write the correct timecode information down and keep the dates straight on the tapes and discs, we should be okay. I can recognize a line of dialog at a glance anyway.

Jay Massengill · December 26th, 2003, 11:37 AM

What you're looking for is called a "Bloop Light". You can buy these new from film production supply houses, they also show up used sometimes at places like Trew Audio and Coffeysound.
Or you can build one yourself if you are good with soldering your own electronics. The better versions emit a strobe-type flash so it doen't have to be on-camera. The simpler versions (home-made) use a high-brightness LED and piezo beeper so it would need to be on-camera. Some versions are also made specifically to wire directly into your audio circuit, I'd probably avoid that to make it simpler.
You can get a basic circuit diagram from Radio Shack. It's a booklet called "Basic timer circuits with the 555IC chip", or something like that. Simply use one of the circuits that creates a bounce-free switch with a single pulse output and no delay. The pulse would be sent in parallel to both the light and the beeper.
One other practice that I've found helps with slating is to have the camera-op call out the camera's timecode. This dispenses with having to remember take numbers.

Mike Rehmus · December 26th, 2003, 01:04 PM

I vote for the audible call-out. Solves a lot of ID problems.

A buzzer would be a bad audio tool since it, well, buzzes. A single sharp sound is what you want so you get a recognizable single spike on the audio waveform.

A strobe can be disorienting and leaves an after-image that may bother the talent if it hits their eyes. I favor a visible and an IR LED. Visible for the crew, IR for the camera. Timed so that the light is on for no more than one frame time or 1/30th of a second. That way you don't have a lot of frames to deal with (Strobes normally have durations way less than a single frame unless they are automatic units).

Depending on your electronic talents, you could detect the video sync signals and trigger the sync marker at an appropriate time and just for one frame time.

You might want to experiment with a relative delay between the LED which turns on and off very fast and your noise-maker which will certainly take longer to turn on and off. A way around that is to use an electronic beep that is mixed into your recorder's input. You can make that fairly short (which helps synching in post) as long as it is longer than one sample period.

Jay Massengill · December 26th, 2003, 02:22 PM

The output pulse of the chip can be set very short, so the impulse from the piezo beeper shows up like a sharp response. The same is true with the response of the LED. Setting them for a duration of a couple of frames seems to work well. It's sharp enough to be precise but wide enough to give leeway on where it fires in relation to the timing of the camera.

December 25th, 2003, 04:26 PM	#1
Marco Leavitt Inner Circle Join Date: Jul 2002 Location: Albany, NY 12210 Posts: 2,652	Strobe suggestion? Anyone use a strobe to sync their sound? I want to get rid of the slateperson. You can never read what's written on the slate anyway, and we don't really have an extra person to clap it. Can anyone recommend a strobe?

December 25th, 2003, 09:14 PM	#2
Charles Papert Wrangler Join Date: Jan 2002 Location: Los Angeles, CA Posts: 6,810	I'm not really clear on this, Marco. What kind of strobe--a photo flash? Most strobes are pretty quiet, so you'd have to get the mike awfully close. I'm not really clear on what you are planning. As far as not being able to read what's on the slate--umm--have someone write more legibly???! Seriously, it can really help to have a visual notation of scene and take for the edit. But that's a separate issue than the sync sound mark(I'm assuming you are rolling a separate DAT or something?) The simplest way with no additional personnel to get a sync mark on both picture and sound is to have the actor clap his hands on camera. If he is way offscreen at the beginning of the shot, just have him do it at the end (i.e. tail slate). __________________ Charles Papert www.charlespapert.com

December 26th, 2003, 01:04 PM	#5
Mike Rehmus Wrangler Join Date: May 2002 Location: Vallejo, California Posts: 4,049	I vote for the audible call-out. Solves a lot of ID problems. A buzzer would be a bad audio tool since it, well, buzzes. A single sharp sound is what you want so you get a recognizable single spike on the audio waveform. A strobe can be disorienting and leaves an after-image that may bother the talent if it hits their eyes. I favor a visible and an IR LED. Visible for the crew, IR for the camera. Timed so that the light is on for no more than one frame time or 1/30th of a second. That way you don't have a lot of frames to deal with (Strobes normally have durations way less than a single frame unless they are automatic units). Depending on your electronic talents, you could detect the video sync signals and trigger the sync marker at an appropriate time and just for one frame time. You might want to experiment with a relative delay between the LED which turns on and off very fast and your noise-maker which will certainly take longer to turn on and off. A way around that is to use an electronic beep that is mixed into your recorder's input. You can make that fairly short (which helps synching in post) as long as it is longer than one sample period. __________________ Mike Rehmus Hey, I can see the carrot at the end of the tunnel!

December 26th, 2003, 09:29 AM	#3
Marco Leavitt Inner Circle Join Date: Jul 2002 Location: Albany, NY 12210 Posts: 2,652	I'm hoping someone makes a strobe that emits a beep when it flashes. I've seen this in movies about making movies anyway. Didn't they use one in "Living in Oblivion"? Anyway, I know it seems pathetic, but at our level, I don't feel I can really trust anyone to write on the friggin slate. Bad information is worse than no information at all. They never seem to do it right and I'm sick of it. Every time the wrong scene number or date gets written down it creates a huge problem in post. Also, when they clap the slate they never seem to stand in the right place so that it's in focus. Yeah, I've thought about having an actor just clap, but I'm worried it will take them out of character and they're whiny enough as it is. If I sound annoyed, I am. We're recording to minidisc, so I figure if I just make sure to write the correct timecode information down and keep the dates straight on the tapes and discs, we should be okay. I can recognize a line of dialog at a glance anyway.

December 26th, 2003, 11:37 AM	#4
Jay Massengill Trustee Join Date: Jul 2003 Location: Burlington Posts: 1,976	What you're looking for is called a "Bloop Light". You can buy these new from film production supply houses, they also show up used sometimes at places like Trew Audio and Coffeysound. Or you can build one yourself if you are good with soldering your own electronics. The better versions emit a strobe-type flash so it doen't have to be on-camera. The simpler versions (home-made) use a high-brightness LED and piezo beeper so it would need to be on-camera. Some versions are also made specifically to wire directly into your audio circuit, I'd probably avoid that to make it simpler. You can get a basic circuit diagram from Radio Shack. It's a booklet called "Basic timer circuits with the 555IC chip", or something like that. Simply use one of the circuits that creates a bounce-free switch with a single pulse output and no delay. The pulse would be sent in parallel to both the light and the beeper. One other practice that I've found helps with slating is to have the camera-op call out the camera's timecode. This dispenses with having to remember take numbers.

December 26th, 2003, 02:22 PM	#6
Jay Massengill Trustee Join Date: Jul 2003 Location: Burlington Posts: 1,976	The output pulse of the chip can be set very short, so the impulse from the piezo beeper shows up like a sharp response. The same is true with the response of the LED. Setting them for a duration of a couple of frames seems to work well. It's sharp enough to be precise but wide enough to give leeway on where it fires in relation to the timing of the camera.