RE: High speed Tesla spark photographs

["Tesla list" <tesla@xxxxxxxxxx>]

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

Terry,

If you are looking for the "dim" stuff, you do really need to go with RAW
conversion and then convert to 16-bit LINEAR TIFF files.  They must be
LINEAR however.  In the digital camera, JPG images are automatically
"stretched" by the processor to map the data into something the eye would
see.  This stretching curve looks somewhat like the BH curve of magnetic
materials if you were to actually look at it.  The same goes when you
convert the RAW to 16-bit NON-LINEAR TIFFs.  The software does an automatic
stretch.  Problem is that when you let the software do the stretch, it
basically throws out the "real dim" information since in most images this
stuff is irrevelant. However, for what you are doing, this information in
the dark is what is important.

Dan


-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Saturday, September 16, 2006 2:13 AM
To: tesla@xxxxxxxxxx
Subject: RE: High speed Tesla spark photographs

Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Again Dan,

At 09:17 PM 9/15/2006, you wrote:
>...
>
>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

I tested the camera's 9MB TIFF images against the 500K JPG images.  I
pumped the brightness and contrast on the original picture.  Then I
subtracted a dark picture from a black exposure to eliminate noise
and then pumped it.

The TIFF images looks like this:

http://drsstc.com/~piranha/PIRANHA/pictures/TIFFtest.jpg

And the JPG images like this.

http://drsstc.com/~piranha/PIRANHA/pictures/JPGtest.jpg

The top left is the original image, the top right is the black
exposure.  The bottom left is the contrast pump and the bottom right
is the subtraction and then the contrast pump.  The images above are
vastly reduced in size for download ease.

So the smaller images are not too bad given the "army I got".  The
smaller images are much easier to deal with so I will stick with them
and only resort to the giant image if I really have to push it.

Happily, the camera is able to pull out a whole lot of "dark"
information ;-))  So things are looking pretty good!!  I tried the
low light video camera and the still camera's enhanced pictures are
just as good! ;-))  I did note that the black reference picture needs
to be taken at the same settings as the good picture without turning
the camera off.  I think it resets during a power off so the noise
does not line up right anymore.

Cheers,

         Terry