Ah yes, I do that when tracing tube curves.
Setup:
- Isolation transformer with series current sense resistor and diode
(1N4007) connects to tube plate/cathode
- Variable negative supply connects to grid/cathode and voltmeter
- Scope to plate (10x probe) and sense resistor, X-Y mode
- Camera pointed at o'scope, as square as possible! (Tripod sits in front
of the bench, so it's about 2-3 feet away. A couple X optical zoom is
enough to fill about half the shot's area with the CRT, reducing spherical
abberation that otherwise comes with a tight shot.)
- Take one shot for every grid voltage you want recorded
Later...
- Crop images
- Draw curves of one bright solid color to fit the trace, and lines of
another color to fit the graticule (if set up well, you should notice the
lines are evenly spaced and have little slope, only a few pixels across the
whole screen)
- Strip away colors less vivid (the original image)
- Superimpose all the line drawings, add labels and finally, save as .GIF.
A lot of steps and hand work, but not bad for having everything on hand.
Tim
--
Deep Fryer: A very philosophical monk.
Website @
http://webpages.charter.net/dawill/tmoranwms
"John Larkin" wrote in message
...
On Sat, 1 Mar 2008 10:30:05 -0600, "Tim Williams"
wrote:
Oh man.. you're a really bad photographer, I mean really really bad!
Your
pictures are composed of 10 x 10 pixels, saved as JPG, and weigh over
500kB, encoded! Once shrunken to screen resolution, it's clear your
pictures are shot at odd angles, out of focus, and encoded with terrible
color loss!
Here's three tips to draw from. I did:
- Shrink by 10x
- Sharpen out-of-focus pictures (not much help)
- Reduce to 16 colors (the additional loss of color depth is a moot
point)
- Optionally, tweak palette (the gray in two pics was too bright)
- Save as 16-color GIF
- Post in all of what... 25 kilobytes?
And guess what, all these steps actually *salvage* the crap you posted.
If
you had merely reduced the original photos and posted them, you could
avoid
this flaming reply quite easily!
Tim
The other trick is to get far away, 3 feet or so, zoom in, and use a
tripod or equivalent to stabilize the camera. Then use Irfanview to
tweak and resize. This one has a lot of info in 85 kbytes.
John