High speed Tesla spark photographs - Terry's Now ;-)

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi All,

It works!!

http://drsstc.com/~piranha/PIRANHA/pictures/Image6a-good.jpg

http://drsstc.com/~piranha/PIRANHA/pictures/Image8a-good.jpg

Here are the setup details before I forget them ;-)

Zoom - To fit the image nicely to the picture.  Does not seem to 
affect light gathering.  Optical zoom only as opposed to stupid software zoom.

Shutter speed - Does not matter much.  Long enough that you get a 
good chance of "catching" an arc. 1/10 and 1/20 sec does well here.

Background sensor noise - Don't worry about trying to fix noise by 
subtraction of a dark frame or anything.  Oddly, that seems to hurt 
more than help.  If your camera does this automatically, I think it 
should be turned off.  The key is a sensitive low noise sensor to begin with!!

Aperture - As big as possible!!  You need to gather as much light as 
you possibly can at all costs!!

Len's - If you have a choice, one that gathers the most light.

ISO - As high as possible!!! 1,000,000 would be nice!!!  Mine only 
goes to 400 at that is barely enough.  One of those cameras that can 
be forced up to 16,000 whether it is good or not would be nice.  You 
really need this one!!!  As Dan and other's say, getting data out of 
the camera in a deep RAW format would really help here too.  The cool 
stuff is just barely above the noise level in my case.

Distance - As close as possible just to gather more light!!

Speed - My four rotating mirror block is running at about 5000 
RPM.  2000 - 6000 RPM would be fine.  I think slower is a bit better 
since more light hits the sensor pixels that way, but you want it to 
be fast enough to separate the pulses.

The room should be very dark to eliminate stray light.

Flash - Be sure to turn that **^*&%* thing off!!!  There you are in 
the dark fiddling with the camera and blammo!!  Almost knocked me over.

Remote shutter is ultra nice!!  If the camera can take pictures 
automatically at say every second that would be very nice too.  But 
you can do the shutter button too.

White Balance - I used daylight, but it is turning out black and 
white mostly in my case as I super pump up the brightness and contrast.

EV - Set it up high to brighten the picture as much as possible, but 
it had no effect in my camera's manual mode.

Reset - Set the camera so it does not loose all the settings when the 
power is turned off ;-)

Focus - Manual.  I just measured it and set the camera to that 
distance.  This could be tricky, but I did not have much trouble with it.

Background - Black felt works fine.

I took about 200 pictures today.  Mostly figuring out by trial and 
error what is good.  Rechargeable batteries are good too but you 
don't use the flash so the battery drain is pretty low.  I did keep 
the LCD screen on all the time.

At 5000 RPM you can just glue the mirror to the little motor shaft or 
whatever.  No need for a fancy machined block.  No need for four 
mirrors, just one would do fine with a longer shutter speed to catch 
a good arc on one of the rotations.

The stray light paths near the mirror should be blocked and all the 
surfaces should be painted black to eliminate stray light reflections.

So it is pretty easy.  I did have to carefully increase brightness 
and contrast with software to see air streamers.  They are barely 
above the noise level.  However, power arcs are very easy to see.  I 
had to go back to all the black frames and lighten them so see if 
there were air streamers.  Power arcs show up right away.

I put a 40.5MB zip file with a lot of pictures here:

http://rapidshare.de/files/33629810/StreakCam.zip.html

At the bottom of the page select "free".
It makes you wait about 2 minutes to read the ads and then a download 
screen comes up.
Enter the funny letters in the robot trap box and save the file.  It 
is just a typical zip file filled with all the JPG images from the 
last "lucky run".  Some are plain and some have been enhanced.  Some 
of those pictures are just black too...  The four read streaks to the 
left or the calibration LED flashing at 100kHz.  Each mirror makes 
it's own streak depending  on the fine alignment of the mirror.  If 
the pulses are blurred out, it is because that mirror scanned twice 
while the shutter was open.

I "think" time increases from bottom to top.  Hard to say since the 
camera is upside down, inverted, twisted, and the motor turns in some 
direction...  "Hard to say for sure" #;-))  I will try to modify the 
calibrator so it gradually goes out to point in the right 
direction.  The calibrator is not really needed but it does prove the 
speed and all.

Thanks to Peter for figuring all this out!!!  I think you are even 
working on an improvement :-))

I don't know what the pictures "mean" yet since Just taking the 
pictures is the deal right now.

Cheers,

	Terry