Flash

[Actor]

Here's an idea that I've been thinking about for some time and this forum seems to be the kind of place which might have the kind of expertise to judge its feasibility. As most or you know, many super8 cameras have a PC or flash contact, a switch which closes when the shutter opens. Its purpose is to trigger a flash and its use is generally limited to single frame exposures in animation.

However, the contact closes each time the shutter opens even if the camera is running at 18 or 24 fps, a fact that is frequently used to generate sync signals for double system sound. I can't help but muse on the possibility of returning the PC to it's orginal intended use and provide 24 flashes per second in sync with the shutter.

Anyone who has used electronic flash in still photography will immediately see the first problem with this idea. Whenever you take a flash picture it takes several seconds for the flash unit to recover and get ready for the next exposure. You can't simply attach a flash to your camera and expect to get 24 flashes per second.

My first idea for getting around this is to use more than one flash. If you search the marketplace and find a model that can recover in one second (perhaps a little optimistic) then use 24 units and come up with some kind of circuit that switches from one unit to the next in a cycle. There are several down sides here, the most obvious being that these units go for a minimum of $20 (one that can recover in one second would probably cost more). 24 of these babies would set me back $480 and that's enough to get me to looking for other solutions to my lighting requirements. Another thing is that you would have to point these things at something like a soft box because light that constantly shifts between 24 point sources has got to produce unwanted effects.

OK. Next idea. My understanding is that the flash is produced by a strobe "bulb" (for lack of a better word). The bulb "fires" for a period of about 1/1000 second when a high voltage capacitor is discharged through it. The reason the unit can fire only once every second or so is because it takes that much time to recharge the capacitor from a circuit powered by a few AA cells. If the capacitor could be recharged in 1/24 of a second could the bulb fire at that rate without quickly burning out?

<font color="#a62a2a" size="1">[ July 12, 2002 02:10 AM: Message edited by: Actor ]</font>

[Nigel]

I don't see why it couldn't work.

Roger seems to be the engineer of the group maybe he has something to say.

Good Luck

[JIM DUNN]

ACTOR---Why?

[MovieStuff]

The idea for synching a strobe has been discussed. I think that Matt Pacini first brought it up last year. The concept is good but, having worked with stobes in our still photo work, I can tell you that the power supply for a single head weighs as much as a motorcycle or tractor battery. You would need one for each strobe, so imagine carrying around 24 lead batteries and you can get an idea of the problem. Also, strobes meant for photographic use are not designed to withstand fast repetition. The heat build up can be pretty intense, even when used with a motor drive at only a few frames per second.

Roger

<font color="#a62a2a" size="1">[ July 12, 2002 09:10 PM: Message edited by: MovieStuff ]</font>

[Cranium]

Even if you could get a "strobe light" to fire in sync with the shutter (think disco...) you'd probably want to vomit by the time you're changing the first roll, if you're not already loading the crew member that collapsed in an epileptic fit into the ambulance.
Just a thought. [img]wink.gif[/img]

[Nigel]

I don't think that you would get a "strobe" effect since the light would flash with each frame--Thus it would be the same as a still Photo--You would'nt necessarily notice it.

Yes, The power packs for still strobes are heavy and you may have to deal with a heavy transformer or some other sort of regulator. But I don't think that you have to deal with 24 of them. There are strobes that can fire in sucession.

I am by no means the expert in this but I say fukk it--go for it if it look like shitt then oh well.

Good Luck

[Nigel]

The altering of words is to get around the commie censors that feel it is best to what we write.

[MovieStuff]

<BLOCKQUOTE><font size=2 face="Verdana, Helvetica, sans-serif">quote:</font><table border="0" width="90%" bgcolor="#333333" cellspacing="1" cellpadding="0"><tr><td width="100%"><table border="0" width="100%" cellspacing="0" cellpadding="2" bgcolor="#FF9900"><tr><td width="100%" bgcolor="#DDDDDD"><font size=2 face="Verdana, Helvetica, sans-serif">Originally posted by Nigel:
I don't think that you would get a "strobe" effect since the light would flash with each frame</font></td></tr></table></td></tr></table></BLOCKQUOTE>

Hi, Nigel!

Cranium isn't talking about the effect on the film. He's talking about the effect on the actors and crew from being under a rapidly strobing light source. Instant convulsions, if you ask me!

<BLOCKQUOTE><font size=2 face="Verdana, Helvetica, sans-serif">quote:</font><table border="0" width="90%" bgcolor="#333333" cellspacing="1" cellpadding="0"><tr><td width="100%"><table border="0" width="100%" cellspacing="0" cellpadding="2" bgcolor="#FF9900"><tr><td width="100%" bgcolor="#DDDDDD"><font size=2 face="Verdana, Helvetica, sans-serif">Originally posted by Nigel:
Yes, The power packs for still strobes are heavy and you may have to deal with a heavy transformer or some other sort of regulator. But I don't think that you have to deal with 24 of them. There are strobes that can fire in sucession.</font></td></tr></table></td></tr></table></BLOCKQUOTE>

Yes, but that isn't they type of flash that Actor was referring to. He was referring to common photographic flash units in the $20 range, in which case you'd need multiples. I was pointing out that, even if you used pro flash heads, they aren't made for the kind of continuous duty implied here and that the power supplies for them are fairly bulky. Therefore, IF multiples were used, the entire package could get quite heavy.

Now, having said that, you can go to Radio Shack and get a flashing strobe in a box that can be plugged into the wall pretty cheap. However, the trigger rate is far below even 18fps. Plus, if you wanted to make that a portable unit, it draws considerable power, which is why photo strobes take so long to recycle from battery power.

Unless you get into hyper effecient LEDs or flourescents, there is a fundamental relationship between power and output when dealing with common light sources such as strobes, tungsten or halogen bulbs. Making the power portable becomes problematic for the latter.

<BLOCKQUOTE><font size=2 face="Verdana, Helvetica, sans-serif">quote:</font><table border="0" width="90%" bgcolor="#333333" cellspacing="1" cellpadding="0"><tr><td width="100%"><table border="0" width="100%" cellspacing="0" cellpadding="2" bgcolor="#FF9900"><tr><td width="100%" bgcolor="#DDDDDD"><font size=2 face="Verdana, Helvetica, sans-serif">Originally posted by Nigel:

I am by no means the expert in this but I say fukk it--go for it if it look like shitt then oh well.</font></td></tr></table></td></tr></table></BLOCKQUOTE>

I agree! If you have the resources, then experiment. There might be a workaround that isn't apparent. I can't tell you how many people told me the WorkPrinter series would be a joke and that the image quality from using a consumer projector would be crappola. I agree with Nigel. Go for it! [img]smile.gif[/img]

Roger

<font color="#a62a2a" size="1">[ July 13, 2002 08:54 AM: Message edited by: MovieStuff ]</font>