A few of the dvx'ers did some work with a Brevis beta and the M2...clips are not active any longer, however I should have these somewhere.

Some furthur testing with the larger motor and weight.

There remains to a lesser degree a fixed pattern artifact. When I stepped the shutter speed up to strobe the groundglass, the orbital pattern has remained elliptoid and remains canted to the left slightly as was the original smaller excursion.

In an earlier post, I had referred to the excursion having become more circular with the extra horsepower and weight. Of course it was, because I had viewed the television set as a strobe and invalidated my research by holding the appliance upright so the light from the CRT would fall on it.

Given the motion remains elliptiod I am convinced the fixed pattern is related to the much slower surface motion which occurs at the end points of the elliptoid excursion.

I am furthur encouraged in this direction by subsequent tests I did with the groundglass removed to see if the optical path alone was generating the fixed pattern. I could not observe any fixed artifacts on the high resolution monitor. This is not to say there aren't any but I could not find them.

Two possible solutions come to mind.

One is to over-drive the excursion with a heavier weight, then limit it to a circular motion by adding fixed pillars to the front of the case which supports the existing moving pillars. On the fixed pillars would rest sleeves which have a very wide clearance both in the groundglass carrier and the pillars.

This method is used for locating and driving caterpillar tracks in a hostile no lube environment. Because of the excessive clearance, the motion is converted to a rolling motion across frictional surfaces rather than a rubbing motion.

The downside is that the motion would become noisier. Think bulldozer or army tank in high speed miniature and you may get the picture. With insulation around the front tube, I think it could be resolved.

At high speeds there likely will be all manner of harmonics and random motions as well as the truly circular ones. There is some randomness in the existing Letus movment which may be why I have been able with some lenses to push to f22 with none other than the fixed pattern artifact turning up.

Another solution might be to add some tension springs to counter the gravity loading and restore the circular motion. These will also serve to maintain added positive retention of the pillars in the front cover.

This has not emerged to become a problem I thought it would with the more violent excursion I have been experimenting with.

i would love it to all work beautifully. the letus fe has the potential to be a cracking adaptor. Just that film of grain and a proper solid nikon mount would be great. hated the flimsy one. the one of the m2 is so solid

I'll be taking a four week break from any experimentation with improving the Letus35 for HD as I have a demo scene to organise and shoot this coming month plus earn the daily bread.

My imaginings of promoting a more circular orbit of the GG is to start with two fine coil springs of about 1/8" diameter such as you find in old copiers, printers or Lexmark Optra S1250 toner cartridges.

The attach points on the groundglass carrier would be midway on each side. The anchor points would be to pins in radius holes bridging the upper cutout space on each side of the upper pillar in the front (base) which holds the base of the pillars.

This method may provoke a "figure of eight" motion of the groundglass which would require more countermass below the motor on the groundglass carrier to counteract.

"Figure of eight" would create an almost stationary spot somewhere on the groundglass which would appear as a very evident patch of fixed pattern.