Originally Posted by Jedi
...still on the subject of anamorphic lens, why can't someone like Chief Mfg offer with their custom mountings plates (the custom ceiling mount plates designed for a particular make & model of projector) a second set of "scope" mounting holes that would position the mount over a corrected center of gravity that balances the whole affair including the added mass of an anamorphic lens/slide assembly. The workaround, I realize, is to mount the stretch lens assembly on a completely separate mount, but the trouble and resulting appearance of doing so is a bit of mess. I would think the weight of the various lenses and slides are similar enough that an alternate set of plate mounting positions could fairly well serve the lot of lens offered.
Here's the deal with mounts, and some reasons why they don't do above:
1) The gimbals made by the mount companies (e.g. RPM/RPA for Chief), aren't designed to handle ANY dynamic (moving) load. Some (e.g. RPM) have micro adjustable set screws and are fairly sensitive to CG position. They are flimsy in the regard of handling a load that moves. They have small gauge sheet metal and only #6 screws to interface to the also thin gauge projector plates.
2) The ubiquitous 1.5" pipe mount is effectively a stiff pendulum. It is also not designed for a dynamic load. Any force applied to a weight on a pendulum will setup up an oscillation (vibration, swinging), it's simple physics. The 1.5" pole mount has nothing to prevent such a vibration and so anything that disturbs such a mounted projector will cause the projector to "swing". It doesn't take much for that to be VERY obvious on screen. People with basement installs and rooms overhead will often complain about just such "vibrations" becasue even footfalls on the floor above can set them up and casue the PJ to vibrate/swing. It is worse the longer the pipe, but it is there even for short ones.
3) Even the heavy duty ceiling plates have some flex and will do so when subjected to a projector movment force. Anyone who has a 1.5" pipe ceiling mount can reach up and just give the projector a "tap" and away it will go. Depending on the pole length, 10 to 30 seconds before coming to complete rest.
4) Finally, a PJ, lens, all the lens and PJ mounting hardware, with a motorized transport can get dangerously close to the weight limits of the gimbals. The Mount companies are no more likely to make a HD gimbal for us (scope people) than Blue Ray is to make anamorphically encoded discs. Market too small.
Now, add a moveable anamorphic to the mix. With or without a motorized transport, these lenses are fairly heavy (well all of them except for AB's new lens that's reported to be light). The big dog Isco III is around 10 lbs. I think Marks MK4 is similar in weight. Even if Chief made a mount with the CG located correctly with the lens in place, when you move it out of place, you just moved a cantilevered 10 lb load ~9" to the other side and completely moved the CG. So one says , well center the lens and get the "Average" CG location. Tried it. Doesn't work (well). Remember that it only takes a hair of a movement of the PJ on the mount to translate to a big movement on the screen that is 50 times larger than the light source, and 12-30 ft away. The tinyest flex in the PJ mount will cause movement of the image and some misalignment on the screen.
Now add a fast CineSlide to the mix. The CineSlide moves these heavy lenses their full travel in 1-2 seconds depending on chosen firmware. 10 lbs, that is accellerated to speed, then decellerated to stop, over ~9" of travel, in 1 second. F=MA, we al remember that from High school physics. "a" is the accelleration and decelleration and those combined with that weight ("m") generate a substantial force that will cause the 1.5" pole mount, the gimbal, and the mount plate to all flex. Result: vibrations on the screen every time you move the lens. For a few seconds anyway (~13 seconds for a 24" pole and a Sim2 C3X when tested).
Some users aren't worried by the short period (no pun intended) of the vibrations. But if I spent $5-$75k on a PJ and then added a high end cylindrical lens, I'd want the best performance. Dealers often want the easiest install. For the extra time it takes to do this right, and mount independently, the picture and result is worth it. Trust me there. The only exception to this is for projectors with more substantial mounts (i.e. not a 1.5" pole mount and RPM/A gimbal).
That's why we make and strongly recommend independent mounts for Anamorphic lenses. They are more trouble to install, but once installed, any vibration experienced in the anamorphic lens and it's mount is invisible to the user on-screen. It's like looking at your computer monitor and holding a clear pane of glass in front of you. You can move the glass all you want and the your eyes won't see the movement. Becasue neither they, nor the monitor is moving. The lens may vibrate (it does not with our mounts due to rigidity) but if it does, the light beam and PJ do not so the image remains stable.
We have worked directly with may customers on a wide variety of mounts for CineSlides and Isco lenses. We have made it as easy as possible to deal with the independent mounts by way of installation templates, and CAD drawings, particularly for popular projectors. If you are going to setup to allow movement the lens, which I also strongly recommend, you will get best results if you mount it independent of the PJ.
But if someone insists, we can make a mount for popular projectors, too .