Pan/Tilt uneven motion correction.

RRA wrote on 12/24/2009, 3:36 AM
Hi,

I have ProDAD Mercalli for correction of micromovenent visible during job without tripod or some unexpected tilts of tripod (for example tele zoom is very sensitive and it's quite impossible to change zoom direction (push button) without influence on movie (of course pilot resolves this problem). Mercalli works very well on Vegas and I'm able to elimante almost every unwanted tilt (sometimes pan/crop correction is necessary to hide distorted area but picture is very steady).

But what about uneven motion during pan/tilt operation ? Is there any plug in which is able to smooth this ? It looks simpler then job which Mercalli has to do (only linear speed recognition and accelerate correction) ... but I can't find any solution in net.

There is a lot of hardware like pan/tilt heads or slides with automatic motion (servomechanism) control but it exceeds my budget. I'm using the simplest home made slide and oil head in tripod. I have seen fast tip from VASST with piece of rubber :-) it works as everything from VASST but only to some extent and it's actually "hardware" solution :-).

I'm looking for plugin or maybe somebody has a good algorithm how to correct this "manually" with help of velocity envelpe ?

Another question : does anybody have experience with slide camera where rails are replaced by pneumatic or magnetic guide ? Some links ... ? I'm asking becouse pneumatic quide is a model of monotonous movent and it eliminates operator at all (puhsing the carriage ones gives hours of movement (friction eliminated)).

Best regards,

Comments

farss wrote on 12/24/2009, 3:46 AM
"Another question : does anybody have experience with slide camera where rails are replaced by pneumatic or magnetic guide ? Some links ... ? I'm asking becouse pneumatic quide is a model of monotonous movent and it eliminates operator at all (puhsing the carriage ones gives hours of movement (friction eliminated))."

I assume you're talking about using maglev or floating on a cushion of air e.g. air hockey puck?

If so, no real knowledge. I've built a simple 2 axis robot, one axis was a linear bearing. We have some camera sliders that use the same kinds of bearing. Pretty cheap and you can built your own rig or buy camera friendly units for a reasonable price. There's some made for 35mm cameras that cost big time but you probably don't need to support that much weight.

I recall seeing a camera pedestal that used air but you need a very smooth floor.
There's also the P+S Skater for tabletops, costs a friggin fortune but there's cheaper knockoffs around.

Bob.



RRA wrote on 12/24/2009, 5:40 AM
Hi,

Yes, I'm thinking about floating on air cushion : I have seen similar solution in foundry and I know it's capable to transport even very heavy castings.

Construction is not very coplex : you need two pipes (rails for camera carrier) which are connected to the air compressor from one side and "blinded" from other side. Pipes have grid of perforation (drilled with very small diameter, usually less than 0.5 mm, but with high density) which pruduces air cushion. Carrier has two "inverted U" sliders (one for each pipe, exactly like you would slang piece of material on the pipe). If You turn on compressor pressure will set up sliders and entire carrier. Now You can push (once) 100 kg with one finger and it will be bauncing from far left to far right restraining spring per hours...

Best regards,
farss wrote on 12/24/2009, 6:00 AM
Whilst it sounds like an interesting idea I can see a few problems.

1) As it's almost frictionless bringing it to a smooth stop could be an issue.

2) Air compressors and escaping air creates noise. Not the way to keep your audio guys happy.

3) Generally you want a camera to either move in a straight line, in fact a very straight line. If not you want it to move in a repeatable fashion.

4) You need a smooth floor. Fine in a studio but existing designs for camera pedestals work very well and don't have any of the other problems. One thing a pedestal also lets you do is move the camera vertically easily and smoothly. This would be difficult if the base is held up by a cushion of air.

By all means though give your idea a try. Place a camera on one of the existing devices and see how well it can track. Not trying to dampen your interest in innovative ideas, I'm very interested in the same thing. On the other hand I do get to play with some of the expensive hardware and see why it's very hard to build gear that does the same job cheaply.

There's another side to this. The good gear is pretty cheap to rent because it lasts and doesn't become obsolete. We base our rental rates for dollies etc at at least 50% of the factor we use for cameras. In the end it just isn't economic to try to build your own, especially if you factor in the cost of your time.

Bob.
RRA wrote on 12/26/2009, 6:27 AM
There are some inconveniences but from the other side to build tool like this in home you need only PVC pipes, vacuum cleaner and Pico driller.

If it is 100% leveled then it's a monotonous movement and You have to "inject" force like in pinball (force regulates speed). If there is some unevenes in level, you will achieve accelerated movement (+ or -). I suppose the bigest problem is connected with sensitivity of air cushion - You can't correct angle of camera (only parralel shots) because You can't even touch the carrier.

But I would like to come back to main question : how to correct uneven motion in Vegas ? I'm relatively new in video business and I'm still wondering that simplest things are impossible to achieve. I can imagine that pan corection plug in ask me to choose one detail and it will regulate linear horizontal speed. It looks very easy...

Did anybody hear about such plugin ?

Best regards,