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Re: photographing coils


From: 	Thornton, Russ #CSR2000[SMTP:ThorntoR-at-rc.pafb.af.mil]
Sent: 	Thursday, October 30, 1997 7:58 AM
To: 	'Tesla discussion Group'
Subject: 	RE: photographing coils

>Subject: 	Re: magnifier config?
>
>
>Also, does anyone have data on the best way to photograph coils? I tried
>with an el-cheapo camera and it didn't work too well. :) Do the standard
>methods for getting lightening work? 
>
>Thanks!
>
>Travis
>
>

There is no single way to photograph electrical discharges.  It all
depends on the
effect that you want.  If you just want the sparks then near darkness
and 1 second exposure should be OK.  Every discharge will be recorded so
that the longer the exposure 
muddier will be the distinction between arcs.
As an advanced amateur photographer, this is how I would do it for
documentary purposes:

Note:  The logistics may depend on the size of your coil(e.g. whether
you operate it indoors or outdoors). 
I would make a double exposure using a tripod and cable release on
manual settings.  The first exposure would be in good light, preferable
diffused.  This will give better
detail and less contrast, particularly outside.  I would set the camera
for a normal to one stop
under exposure(personally leaning toward the one stop under).  
Then cock your shutter without advancing the film or moving the camera.
I realize this is not possible for most modern point and shoot cameras.
Now, set the cameras aperture two stops down from wide open. (i.e. if
your camera lens is a f2.8 then open it to f5.6).  this will give
adequate depth-of-field assuming your coil is not more than a few feet
wide.  Now here is where your personal artistic abilities come in.
Decide if you want to record a lot of arcs or just a few.  This will
determine your exposure time.  I would recommend 1/15 second for a few
to 5 seconds for many.  If you choose to go for the longer times you may
want to reduce the first exposure some more depending on any ambient
light that is around or generated by the coil itself.   One other
caution I would make is to place some kind of opaque guard over the gap.
 This point source can overwhelm the film at worst and at best cause
distracting and disappointing flare in the lens.
Now you're ready to turn the lights out or wait for the sun to go down
and fire off that second shot.  Stability, rigidity and careful handling
when cocking the shutter for the second exposure is very critical for
acceptable results.
Since I presently don't have a coil to photograph, if anyone uses this
technique I would like to see or hear about the results, successful or
not. ;-))

>Russ Thornton
>CSR 2040, 
>Building 989, Rm.  A1-N20
>Phone: (407) 494-6430 
>Email: thorntor-at-rs.pafb.af.mil
>
>