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how can I take a photo of capacitive discharge

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quicksilver

Fri Aug 13 2010, 07:03PM

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

radiotech wrote ...

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.

You're right on the money! (no pun intended). One of the reasons why I have not invested in a high-end body is that the more I discuss these issues the more I see the delicate nature of the digital. In certain other situations there is no room for film; digital has so much to offer.

But you give something; you get something. Life is always a trade-off. I have always tried to determine what real giants of photography (wild-life nature stuff like National Geo. and many of the news services) take along when on a serious shoot. And there are always one or two film bodies packed away. Many an old Pentax or Nikon has survived a War correspondent's gentle hand.
That may be why many of the mid-level digitalis are selling so much. Because a major high-end digital's life may be in too much jeopardy.

Dave Marshall

Fri Aug 13 2010, 10:18PM

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

I shoot exclusively in digital, and my Olympus E-510 (compact body DSLR) has taken hundreds of photos of the sun, close proximity lightning strikes, electrical discharges of various sorts, and high intensity lights. I've never experienced any kind of sensor issues or burn-in, nor have I heard of it happening with modern cameras. Obviously you have to know how to use the aperture, but I've yet to figure out how to cook anything.

-Dave

Bjørn

Fri Aug 13 2010, 10:29PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

Is there any danger that the spark burst could destroy and imprint the sensor face of the digital camera?

As long as you don't go blind by watching it the camera will take it fine. You can photograph the sun or anything else, just avoid long exposures.

A 1 W laser and the sun will damage the chip with long enough exposure. In the laser case it does not have to be very long.

teravolt

Sat Aug 14 2010, 01:38AM

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

my camera is a D80 its been a while since I have used it. but it also has bulb mode so I will have to do a little reading. I am great with electronics but not so with cameras. once I have setup the marx I will come back to this thread. I have found the shutter release port on the side of the D80 and if I get this right I should be able to open the shutter by closing the port pins and then closing the shutter on release. If this is the case I should be able to create a circuit that will open and then close apon the flash with a delay. I am also concerned about EMI, if I use any wires out of the camera I will probly have to shield it. Wat do you think.
+

Bjørn

Sat Aug 14 2010, 02:39AM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

If you keep a reasonable distance the camera will most likely be fine, they are generally well made. Remember to disable the autofocus if you want minimum delay.

If got the code for triggering the camera with an infrared signal but unless you got a micrcontroller the circuit is going to be complicated.

Hon1nbo

Sat Aug 14 2010, 03:14PM

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

teravolt wrote ...

my camera is a D80 its been a while since I have used it. but it also has bulb mode so I will have to do a little reading. I am great with electronics but not so with cameras. once I have setup the marx I will come back to this thread. I have found the shutter release port on the side of the D80 and if I get this right I should be able to open the shutter by closing the port pins and then closing the shutter on release. If this is the case I should be able to create a circuit that will open and then close apon the flash with a delay. I am also concerned about EMI, if I use any wires out of the camera I will probly have to shield it. Wat do you think.
+

if you want, you can go with the optical isolation I referred to earlier, or you can just shield it pretty easily. Also, controller circuits are very easy to build and do not require a microcontroller, but it does allow for adjustable timing.
Also, if you have the circuit trigger the flash as primary control, rather than the camera, you can build an even easier circuit because osolation is not so much of an issue (unless you have a digital flash, in which case that will be a different story). Except for today's modern flashes, many hot-shoe based flashes are primarily controlled by two pins on the mount that short to the capacitor/bulb circuit and trigger transformer on the flash. I don't recall if it has an internal isolation to the HV line or if the camera was supposed to use an SCR (I always used an SCR to interchange with parts that needed it). You can also build a flash you can sacrifice out of a Disposable Camera body (free from many photo labs once you tell them it's for a student project, of course it's a used one). Those you have to use an SCR, but if your Marx fries it it's not a big concern.

Also, and pardon my asking if I'm missing something, but why would you want to use a flash to photograph the output of a Marx? Would you not drown out the spark? I understand my post deals with flashes mostly, but I thought I'd tell you anyways even if I don't understand it.

-Jimmy

teravolt

Sat Aug 14 2010, 04:41PM

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

DaJJHman and BjÃ¸rn there is a infrared remote and the manual states that can be used in bulb moad. have you tried this?

Sat Aug 14 2010, 05:35PM

Registered Member #2372 Joined:
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Posts: 62

The best way to do this, and the way that most people do it (for time integrated photos) is to use a pinhole and a long exposure. If you have a SLR camera you can use the cover for the camera body (when no lens is present) and install a small pinhole in the middle of it (no focusing required). Then just use a multi second exposure time and fire the pulsed power system. You dont even have to dim the lights in the room and you will still get a good picture because the flash from the discharge is so bright. This technique is used by lots of people on large (GW to TW) discharges and the SLR cameras are pretty good about surviving, you can put it in a shielded box if you want and just leave a small hole in the box in front of the camera pinhole. The remote triggering can be done by using a small audio jack and shorting two of the pins (the other pin is for autofocus, at least on Canon SLR cameras).

Bjørn

Sat Aug 14 2010, 05:56PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

DaJJHman and BjÃ¸rn there is a infrared remote and the manual states that can be used in bulb moad. have you tried this?

Yes, the first signal opens the shutter, the second one closes it. The remotes can be had very cheap on e-bay or other places or you can make your own.

why would you want to use a flash to photograph the output of a Marx? Would you not drown out the spark?

If you use the correct setting you would get the correct balance between the spark and the background, it all depends on how you want the picture to look.

Akika

Sat Aug 14 2010, 08:40PM

Registered Member #1449 Joined: Sun Apr 20 2008, 04:10PM
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Posts: 4

I saw a quite interesting article recently here about lighting photography: Here I think it could be easily modified for Marx discharge photography. Although I haven't built this circuit yet, because I don't have a dslr camera, but others stated that this device is working only when the camera is in full manual mode!

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