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Registered Member #480
Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644
iceowl -
Your "night" photos will look better if the coil is not operating in complete darkness; have some low level of ambient lighting coming from behind the camera position so some details of the coil itself can be seen. Streamers just originating from a point in total darkness are not as interesting as being able to see where they are coming from.
Best results will be obtained if your camera allows full manual exposure control; if it's a digital camera, its almost essential that it has a manual focus mode (or at least allows focus lock), as the real-time autofocus function will usually get hopelessly confused by the thin, bright, constantly-moving streamers.
Here are some general recommendations: 1. Camera must be mounted on a tripod; 2. Use an effective film speed or sensitivity of ASA100 or ASA200; 3. Use an aperture of f5.6 to f11; smaller apertures will provide increased depth of field. 4. Position a grounded strike target off to one side of the topload, perpendicular to the camera's line-of-sight, so you will be able to see the maximum streamer length. When properly tuned, your spark-gap coil will generate maximum streamer lenght without a long breakout point. Put a "breakout point" on your grounded target, and the streamers will try to connect with it. 5. Pre-focus the camera on the edge of the toroid nearest to the strike target; 6. Experiment with different shutter speeds to see what provides the most pleasing visual effects. Typical shutter speeds will be from 1/4 second to 3 seconds, depending how the coil's performance level, breakrate, and how much "banjo effect" you want to capture. 7. Try to fabricate some kind of light-tight but vented enclosure for your spark gap. One of the most common causes of poor TC photos is light contamination from the extremely bright light from the spark gap "washing out" details of the coil and streamers.
To start, just make a series of test shots at shutter speeds of 1/8 sec to 4 seconds, and apertures of f5.6 to f11.
Once you can see what general settings generate the most pleasing images with your particular camera and coil setup, you can make more subtle adjustments. There will be no single setting that's "best", as different shutter speeds will generate very different looks to the streamers.
It's been my experience that film cameras will capture a lot of tiny sub-streamers and corona artifacts that digital cameras, even high-end models, will not.
Thanks so much for the help! I will give that a try. I was so excited last eve that I couldn't get the camera set up in any useful way. Now that I have some time to consider it, I will try your advice.
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