RE: Photo Question

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Rothman, Aric by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Aric.Rothman-at-Honeywell-dot-com>

In my opinion, the best results are obtained by double exposure.  Double
exposure allows for an image that includes both a properly exposed coil
setup, as well as complete control over the quantity of streamers.  

You must have a camera that allows double exposing for this procedure to
work.  A tripod is preferable, but placing the camera on a sandbag,
supported by a stable surface, is acceptable.  A cable or remote release is
a very desirable accessory.

Use color or black and white print film.  Slide film does not have nearly
the exposure latitude of print film.  Since the camera will be stationary,
you will probably get better results with slower speed film.  One film is
particular is Fuji Acros B&W print film.  It is an excellent choice for long
exposures ( 1 second or more ), as it does not suffer from much reciprocity
failure. Reciprocity failure is a loss in real film speed as exposure time
increases.  However, if images of single streamers are desired, try using a
higher speed film, as exposure times will have to be short.

Here is the double exposure procedure:

1) Mount camera on tripod.

2) Compose image through viewfinder, focusing on the secondary coil.
Advance film and set for multiple exposure.  If possible, set camera to
auto-expose in aperture priority mode, and adjust aperture for desired depth
of field (how much fore/background is in focus).  If exposure compensation
is available on your camera, set it for +1/3 stop.

3) Under normal lighting, release the shutter through the cable release or
remote.  Let the camera's auto-exposure function set the shutter speed.

Now, prepare to take the streamer image.

4) Set the camera to full manual control.  Set aperture to f/5.6 to f/8
(usually, a lens' performance, in terms of sharpness, is maximized in the
middle of its aperture range).  Set shutter speed to 1/30 second.  If using
400 speed film or above, single streamer images are desired, try starting at
1/125 second.

5) Turn off lights, turn on the coil, and snap the picture.

6) Deactivate multi-exposure mode on the camera, advance film.

7) Repeat steps 2 through 6, decreasing the shutter speed in step 4 until an
exposure time of 2 seconds is reached.

This technique should give you a good range of streamer quantities and
intensities.  Results of double exposing a TC can be seen at
http://lightningboy.n3-dot-net.

Aric