Some photos from the 2006 Early Television Convention are now up at:

http://www.njarc.org/ETF_2006/

http://audiokarma.org/forums/attachment.php?attachmentid=15037 (http://www.njarc.org/ETF_2006/)

Thanks to Richard Dean and Tom Genova for many of the pics!

--Dave Sica

Did anyone get a good photo of Peter Yancer's mirror screw demonstration?

Here are some of the better ones I took - the shutter speed was 1/2 second, so I had two problems: camera shake (no tripod) and any movement of the actors.

BTW, this is the first moment I've had to do any sorting - probably should send some originals to Peter, but I'm going to bed now to nurse this cold.

The picture was excellent on the mirror screws. The camera is picking up the lines. I was really amazed that he was able to pull this off.


polaraman

I was never that fascinated by mechanical TV, though the high prices of the hardware made it easy not to collect it. But the mirror screw is amazing. I am going to have to build one for myself!

Thanks for the photos, Wayne.

I had two problems: camera shake (no tripod) and any movement of the actors.


Still, some of the better photos I've seen of the image from a mirror screw television!

--Dave

I haven't heard of the mirror screw system, is there a web page description of it or could you tell me the principle?

This is THE web site for info on the mirror screw (and other mechanical tv's)

http://www.televisionexperimenters.com/

Darryl

I was at the convention and saw the mirror screw demo. These photos are about as good as you can get with a still picture. But they still don't do justice to the live image, which was bright and quite watchable. More than one presenter noted that moving images look much better than still images on lo-res mechanical TVs.

I thought I saw one or two people trying to take video of the mirror screw. I don't know if that would turn out better, or if you'd just get loads of flicker due to different frame rates or whatever.

I saw one or two people trying to take video of the mirror screw. I don't know if that would turn out better, or if you'd just get loads of flicker due to different frame rates or whatever.

NTSC video of the mirror screw turns out absolutely wretchedly, as does video coverage of the CBS color system, the Col-R-Tel converter, film projectors, DLP projection and virtually anything else that's not exactly the same frame rate as the camera.

And don't forget The Narrow Bandwidth Television Association (http://www.nbtv.org/)

--Dave Sica

Here's the only half-way decent shot I got of the Empire mechanical TV at the ETF convention This set has 45 lines, 3:1 interlace. The exposure was 1/2 second, hand-held, and the result was still very dim. I processed the image by increasing the gain about 2 or 2.5 times. You should be able to make out the subject, which was converted to this format from NTSC. I suggest viewing this from far away. I don't know if the three fields were really so different in brightness as they appear.

If Steve McVoy is reading, can you tell us what the light source is? Looks neon-color, but could be using an LED.

Interesting how, in the thumbnails, I can make out the subject pretty good, even tell just what it's from, but when I look at the images full size I lose all that. I do find mechanical television fascinating and wish I could have been there for this demonstration. I did recently see mechanical television for the first time, thanks to the tiny unit on display at the RHS museum here in MD. I had a hard time pulling myself away from that little thing!

Here's more photos from this year's Convention. Thank Wayne Bretl for the HUGE batch of excellent quality pictures. [photos (http://www.njarc.org/ETF_2006/index1.htm)]

(The original batch is still located here (http://www.njarc.org/ETF_2006/).)

The light source for the Western Empire State picture above is an original neon crater lamp:

http://www.earlytelevision.org/western_empire.html

http://www.earlytelevision.org/western_empire_restoration.html

Before I found one, I experimented with using a LED. The problem is the aperture size. In order to resolve the 45 lines in the picture, the aperture has to be 20 mils or less. LEDs are made with apertures that small, but they aren't very bright. High intensity LEDs are made by putting several next to each other, and thereby increasing the aperture to 40 mils or more. You get a brighter picture, but less resolution (and you sure can't spare any resolution with only 45 lines).

The other problem is the dispersion angle. The light source has to have a wide enough beam to illuminate all 45 lenses in the disk, which is located about 2 inches from the source. The distance from the outermost lens to the innermost one on the disk is about 1/2 inch, so you need about a 15 degree beam width. Without this requirement, a laser of some sort might work.

There must be some way to use a condensing lens arrangement to reduce the size of the spot from a high power LED, but I don't know enough about optics to do it. If anyone has any ideas, I'd like to hear them.

The other problem is the dispersion angle. The light source has to have a wide enough beam to illuminate all 45 lenses in the disk, which is located about 2 inches from the source. The distance from the outermost lens to the innermost one on the disk is about 1/2 inch, so you need about a 15 degree beam width. Without this requirement, a laser of some sort might work.

There must be some way to use a condensing lens arrangement to reduce the size of the spot from a high power LED, but I don't know enough about optics to do it. If anyone has any ideas, I'd like to hear them.


Without major modifications to all the optics including the lenses on the disc, I'd guess it can't be done - the system essentially projects the image of the crater as a spot on the screen, I believe, and has a fixed magnification, so increasing the size of the source necessarily increases the size of the spot.