RE: High speed Tesla spark photographs

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Daniel McCauley" <dhmccauley@xxxxxxxxxxxxxxxxxxxxxxxxxx>

Terry,

Since you are using a camera that produces considerable noise with even
relatively short exposures (a few seconds), it would be important to use as
short an exposure as possible to reduce noise build-up on the frame.
Remember, you may only be capturing say a 10us arc (i'm guessing on the
actual duration here), but if you are leaving the shutter open for even 1
second,  you are still capturing noise for that entire second which just
integrates over time.

Also, you mention color balance and all that jazz, but if you really want to
be serious with these images, you REALLY do need to shoot RAW images and
convert them to TIFF files using 16-bit linear mode.  With RAW images, it
doesn't matter what your color balance is as  you can select this when you
do the RAW conversion.  Also, when shooting JPG you only get 8-bit of
information vs. 12-bit.  Of course, you could argue that that added
resolution might not be that important when shooting a bright object like an
arc.

Dan


Yes!  Of course!!  So one does not need super high shutter speeds and
all.  I can see some advantage too in covering the other area the
mirror scans areas with black painted surfaces just to cut down on
stray light.  The SISG can fire in single shot mode more or less just
by using big 200K charging resistors.  I am thinking of increasing
the light sensitivity as much as possible.

>If you don't catch anything just try again.  Too long an exposure
>will just overlap sparks. With my current guesses about 50% of
>photos are OK. All my pics are taken with an infrared remote
>trigger, but camera shake is not an issue with these type of events.

I figure once it is set up and going, I just click the remote until
the camera memory fills up.

>Colour balance can be done automatically by the camera or software
>later but auto colour balance of a purple spark will give a green
>background. Manual balance is easy enough and twiddling is needed to
>bring out the really faint events like the "second harmonic" line
>between the main ringdown channels.

I think "daylight" does fine.  Everything looks "right" there for me.

>My motor speed is slower but my camera is better.  A bigger mirror
>might really help.

I am thinking about adding another fixed flat mirror just to give a
better angle advantage.  But I will have to get something to work
first before I go "fixing" anything ;-)


>Time is an issue with me and due to work, I can rarely do anything
>during the working week.  Last week though I was off sick with the
>flu - but not so sick I couldn't work in the shed.

Just quit the day job like I did :-))

>I am looking forward to Terrys "first light".

Still waiting on the mirrors.....

Cheers,

         Terry


>Peter
......