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how can I take a photo of capacitive discharge

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teravolt

Thu Aug 12 2010, 03:37AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

I have D70 nikon and a S700 nikon and I find it hard to take a picture of a marx discharge of a single arc recommendations welcome. I made a short video of a trippler and it didn't show all the arcs when I viewed it on youtube. It was discharging at about 1 hz and you can here it in the video but no display does anybody think that there is a problem wit the uploading.

Mads Barnkob

Thu Aug 12 2010, 03:56AM

Registered Member #1403 Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968

The rise and fall times on a Marx generator breakdown is usually very low values due to the very low capacitances used, so you would need a high speed camera to catch all the discharges...

My best bet would be some way to sync you marx and camera, but then again, you would properly need some expensive camera to use sound triggering in movie move, if it even exists...

Just my thoughts... :)

radiotech

Thu Aug 12 2010, 04:17AM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

Klydonograms were the records of sparks made on photographic plates in a dark box in an instrument called a klydonograph that was used to record strikes on power towers.

Is there an equivalent of just opening the shutter in a digital camera?

GluD

Thu Aug 12 2010, 12:59PM

Registered Member #1221 Joined: Wed Jan 09 2008, 06:17PM
Location: Odense, Denmark
Posts: 196

When I got the picture for my avatar, we just shot the camera as fast as it could until we got a picture of a spark, it took a while but sure faster then building a rig.

Dave Marshall

Thu Aug 12 2010, 01:20PM

Registered Member #16 Joined: Thu Feb 02 2006, 02:22PM
Location: New Wilmington, PA
Posts: 554

The D70 is capable of operating in bulb mode, or timed long exposure. Just open the shutter in a dim room and leave it open until the marx has fired, then let it close.

Same principle for lightning photography.

-Dave

Matt Edwards

Thu Aug 12 2010, 11:49PM

Registered Member #2838 Joined: Fri Apr 30 2010, 07:55PM
Location: tehachapi, CA
Posts: 333

Dave Marshall's suggestion would be the easiest solution to your problem. Simply set your camera for say 0.5sec or so and place it somewhere stable so that it does not shake or move. A tripod would be a good idea if you have one available. Trigger the shutter to open and quickly fire the generator. You should get a pretty nice photograph this way.

Another option, if you would like to create a circuit, is to use a sound activated trigger for the shutter that will trigger the camera to take the photo when the snap of the arc is heard from the discharge. You can build one similar to this.

But honestly, I would just use a slow shutter speed.

As far as the video, (considering that I have not seen it) I would recommend makeing sure that there is no visible sunlight entering the frame. If you have ever tried to view even a nice tesla coil outside during the day you will understand why. Try a fairly dark environment. This might possibly solve your video problem. Also, fps may be an issue but not likely.

teravolt

Fri Aug 13 2010, 02:08AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

thanks Dave Marshall and Oidium45 and all. It seems that a open shutter is the way to go for a marx. the marx I want to take a picture of is the first section of my 2mev marx as poasted in the projects forum. I am not shure how intense the arc will be and I am a little concerned about damaging the ccd. Should I use a filter to start with? Dave I will have to expieriment but will have to setup certain levels of backlighting so the spark and marx visible at he same time? Thanks N.B.

quicksilver

Fri Aug 13 2010, 03:36PM

Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679

I use film almost exclusively and Dave's post is not only the most functional but generally the most exacting and clear. - not to mention the most flexible.

Digital is substantially different than film in this area. While film allows for vastly for flexibility in the final work, film cameras also have (generally) more of an elegant shutter speed mechanism. but it's not something "written in stone".

When using techniques like that, background ambient light most be examined and occasionally any background light should be deal with.

IF you REALLY want to get good shots, go to most any discussion on shooting similar project (lightning is fine as are pyrotechnics) and read up on what people have done with YOUR equipment in specifics. There are OFTEN little "tricks" and techniques that you wouldn't guess by simple logical deduction.

Hon1nbo

Fri Aug 13 2010, 05:51PM

Registered Member #902 Joined: Sun Jul 15 2007, 08:17PM
Location: North Texas
Posts: 1040

a simple trick, as an alternative to a long shutter which is just as good, is to make a circuit that ties into your marx Trigger. a little inductor or something that detects the pulse or trigger if you have one, and use a string (yes, a string!) of optoisolators or a fiber optic cable to isolate the camera and have that feed into the "cable release" control of the camera to trigger the shutter. The normal high speed solution using sound might not respond fast enough to capture this but it takes only five minutes to build on a breadboard and three parts, so if you have them you might give it a try.

-Jimmy

radiotech

Fri Aug 13 2010, 06:08PM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

The film surely could absorb all the radiant energy from the discharge, Is there any danger that the spark burst could destroy and imprint the sensor face of the digital camera? Old vidicons and CCD sensors in handicams often got burnt with specks even if sunlight glanced off something reflective.

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