This post is the first in a number of experiments with a pan & tilt yoke that I’m fortunate enough to have in my workshop to experiment with!

Although designed mainly to allow static theatre light fixtures to pan and tilt I think the Right Arm has many more creative possibilities and not only on the stage, think projectors, cameras, speakers, lasers, snow machines etc.  In later posts I’ll be using it to do everything from smooth moving time-lapse video to an automated follow spot that will actually track a person on stage!

The Right Arm is designed and built by US (Indiana) based company Apollo Design Technology who specialise in theatrical and architectural lighting products and accessories. This first experiment is actually a re-creation of a successful use of the Right Arm  that I unfortunately failed to document properly!

I first came across the Right Arm in a trade brochure that was lying around the Abbey Theatre control room about three years ago. I knew it would be very useful to me at some stage, I just didn’t realise how soon. As detailed in this post, I was brought in on the first ever staged production of Stephen King’s The Shawshank Redemption by Dublin, Ireland based theatre company Lane Productions. I was given about three days to create a projected version of an effect that involved a mechanical butterfly ‘flying’ from about waist high up to the grid (about 7m). The reason the original was being replaced was because it wasn’t convincing or controllable enough and it was a major set piece of the finale.

The digital replacement involved an animated 3D model of the butterfly, and a projector powerful enough to project a small butterfly over a huge area – we went with a Barco CLM HD8 – an 8k Lumen 1080p DLP projector. It all worked perfectly in the end (see original post for stressful moments!) but it was an expensive and very touring unfriendly solution due to size / weight / noise issues.

So when it was announced that the show would go to Wyndham’s theatre in London’s West End I wasn’t surprised to be asked if there was any other way to do it. Enter the Right Arm. My idea was to replace the large, powerful, expensive and loud projector with a smaller, lighter, cheaper & quieter one and mechanically move it around to make the butterfly fly! This is exactly what we did with Shawshank Redemption in the West End and it worked faultlessly for the full run of over six months.

The design of the arm itself makes it very easy to mount a variety of fixtures and objects to it. Apollo didn’t over complicate this at all and the resulting set of equally spaced mounting holes are really all that’s needed. The unit is constructed in heavy duty cast parts that are definitely built to last. It’s weight without a fixture attached is 12.7kg and it can carry a load of 17.1kg, which is quite impressive.

The clip below is a short clip show the Right Arm moving through part of it’s start up routine with a 2k5 lumen projector mounted to the arm. The Right Arm can handle a load of 18.1kg – once it’d properly balanced (more in this later) which opens up a lot of possibilities in terms of lamps, cameras, projectors etc. The range of motion of the Right Arm is 300° pan and 270° tilt, speeds are 180° in 6 seconds on both axes. In my photos and clips you’ll notice that the Right Arm is up-rigged from a bar – this is simply because I didn’t have a decent bar at height rigged so I put this floor stand together. I’m not entirely sure if it’s designed to be mounted like this – but it does make it more useful as a camera head!

This next clip goes through a basic pass of the butterfly projection – it is obviously scaled down in terms of room size and throw distance but the demonstration is clear. The Right Arm is controlled via DMX512 and it has standard 5 pin input and output. The software I’m using to control the Right Arm is custom software for this show and uses a USB / DMX interface to output DMX. The software synchronised the video playback from the projector with the motion of the Right Arm. It also allowed for the flight path of the butterfly to be very accurately and graphically defined – for example it was programmed to avoid a poster on the cell wall in the set.

The Right Arm can be used in 8-bit or 16-bit mode depending on the required accuracy and / or range of movement required. In 16-bit mode the motion is incredibly smooth – the two powerful stepper motors are obviously being micro-stepped in this mode but the quality construction of the unit definitely contributes to the smooth motion even at very low speeds. I have even started experimenting with shooting some HD video using the Right Arm – stay tuned for the next post!

Addressing the unit is pretty straight forward using the mechanical buttons and display:

I’ve noticed that this has been replaced with the addition of digital buttons and an LCD panel on the Right Arm 2. Care needs to taken when mounting a load onto the Right Arm bracket as it needs to be correctly balanced to ensure even weight distribution through the range of the Right Arms motion. A simple but robust feature handles this – the bracket can be slid toward and away from the tilt pivot  point. Together with the multiple mounting holes on the bracket, this allows the load to be mounted with it’s centre of gravity in line with the two axes of motion.

Another indication of the build quality of the Right Arm are details that are often over looked. For example the stress relief boots on the cabling to the unit are of the right size and stiffness to properly protect the cables from wear and tear and life on the road. Also visible in this image is the rail (not sure what it’s actually called) that’s cast as part of the body of the unit itself – it’s incredibly useful for cable-tying all sorts of cables on there, and care does have to be taken when doing this as the stuff that you mount on the arm will be moving!

More photos below and stay tuned for the automated follow spot!

From artist Sarah Browne’s website

… In the gallery, a ‘countdown clock’ is marking the final days of the franc, producing a stock market inspired, ticker tape output of the days, hours, minutes and seconds alongside a live data stream of euro exchange rates—to the dollar (in flux) and the franc (fixed). This paradoxical object, which accumulates masses of paper as it measures time running out, is also the catalyst for a 16mm film made by the artist in Le Blanc. With the participation of local shopkeepers and residents, a staged procession carries the clock from the modern part of the city to the old.
…

I built this machine for Sarah Browne for her solo exhibition Second Burial at Le Blanc at Project Arts Centre. It uses a heavily modified dot-matrix receipt printer to print a countdown to when the Franc is no longer legal tender in France and prints live stock information from the internet. The machine is completely wireless and battery powered and uses WiFi to connect to the internet. Using three 12v batteries, the whole thing can last up to 12 hours between recharges. The Arduino microtroller turns the printer and WiFi shield off between prints (every 5 minutes) to conserve power.

Other challenges included modifying a 16mm film reel to act as a paper spool.

earlier this year I had absolutely amazing fun working with the THISISPOPBABY crew Philly, Jenny and Adam, director Wayne Jordan, composer Raymond Scannell and a truly out of this world cast. oh and I got to play around with possibly the sweetest LED video wall in existence. Check out some of the stills below, i’ll upload a couple of video clips soon. If this is what THISISPOPBABY consider a work in progress presentation – I have no idea what will be involved in a full ‘mad owravit’ production! Definitely stay tuned.

Unlucky in love, Corkonian Alice is all set for her sister’s wedding (always the bridesmaid and never the bride), when a chance encounter with delivery boy Warren sends her spiraling through the Dublin streets.

In an epic chase for love on the strangest night of her life, Alice tumbles through the dark, bombarded by grinning politicians, pyjamaclad bowsies, egg heads on the edge, the self help mafia, media gargoyles, twisted scissor sisters, and of course, Delores – The Queen of Hartstown.

Things sure ain’t what they used to be. The looking glass is well and truly cracked. But is true love possible on the other side… or is this town just full of clowns?

Following a bumper 2010 season with WERK at the Abbey, Queer Notions at Project Arts Centre and huge success at Electric Picnic, THISISPOPBABY bring you a modern day fairy tale for the electropop generation. Full of explosive tunes, unforgettable characters and crackling action, this is a work-in-progress presentation of an essential new musical about the here and the now.

video design, projection design, LED video wall, Max/Jitter

Check out some of their large-scale outdoor pieces… a giant spider and The Elephant at La Galerie Des Machines in Nantes
Their website is well worth a look, there are some lovely photographs documenting various large projects. We also caught a brilliant Pierrick Sorin exhibition at the 104, nice day.

]]> http://www.secretspaces.org/la-machine-carousel/feed/ 0 http://www.secretspaces.org/projector-revolve/ http://www.secretspaces.org/projector-revolve/#comments Fri, 07 Jan 2011 20:29:53 +0000 admin http://www.secretspaces.org/?p=197

This was a really interesting project. For an exhibition in Project Arts Centre called A Landscape of Known Facts by artist Katya Sander, I built a machine that rotated first a camera then a projector, continuously, accurately and at very low speeds.

The revolve was to be ready before the piece was made as footage needed to be shot on a DSLR camera using the revolve and then projected in a gallery using a modified version of the revolve at exactly the same speed. The required speed of rotation was 1/3 of revolution per minute or 0.333 RPM, which is very slow indeed.

Briefly. I used a motor, bearing and mount assembly from a dead Martin moving light fixture (I had to replace the actual bearing, motor and belt). Moving heads (movers) are amazing contraptions to disassemble and a dream for inventors and fabricators. I think it’s a marvel that often 20 or more of these things hang over a stage, doing their thing, with hardly anyone noticing. They are among the most sophisticated off-the-shelf ‘robots’ out there.

Mechanical power is provided by a stepper motor and transmitted via synchronous belt and pulley train. The pulley configuration provides slightly higher gear ratio, but not enough in hindsight – if I had anticipated a video stuttering problem (see below) at this stage, I probably would have used a gearhead stepper motor with a much higher ratio, (75 or 100:1 maybe) and driven the stepper at a higher speed.

My design placed the projector and video playback device on the revolve and the audio playback device off the revolve. That the image was to continuously rotate meant that power to the projector (and playback device) needed to pass through a slip ring as cables would have coiled and jammed. This was the reason for having the playback device (a MacBook Pro) on the revolve (after the slip ring) as high quality slip rings with enough circuits and noise shielding to allow for video or data to pass through were super expensive, but they do exist. The slipring I chose was a mercury disc type one – pretty amazing things. Instead of rings of metal (gold in the high end ones) and contacts, this one had discs of liquid metal (mercury) so that continuity with the rotating contact in each circuit couldn’t break – so no noise!

I used a three circuit slip ring to get power and earth to the revolve platform to power the projector and laptop (care must be taken to select a slip ring that has a sufficient current capacity). I wish I had photos of this, but the Mac transformer was attached to the back of the projector using sawn-off RCA jacks – glued to one side of the transformer which then attached to the back of the projector using it’s RCA sockets. nerdy triumph.

The stepper controller I used was from Jaf Motion (I fried an Arduino Stepper shield) and was controlled over USB from a Processing application. The Processing app was on a machine off the revolve – it played the audio and controlled video playback on the laptop over an ad-hoc WiFi connection.

The video below show a test of the mercury slip ring – the projector can rotate continuously while powered on. Note the mount with shelf for laptop under the projector. Mount was made in sheet metal and spaced using PCB standoffs. (apologies for terrible video quality)

The video below shows some footage captured using the revolve using a Canon DLSR camera. It may not show here but viewed at full resolution some slight but regular jitter was visible on all of the footage. I gave some possible reasons for this to the artist during shooting (see copy of suggestions below). The main reason (I think) was down to the individual steps of the motor registering on the footage due to the low speed – this is why a geared stepper would have been better (more steps per revolution). I removed all of the jitter completely using the amazing Virtualdub (had the best stabilisation results for this particular problem out of any software I tried, including After Effects, Premiere and Final Cut Pro). It takes a while to set up suitable passes but it was worth it.

Some suggestions I gave while we were trying to figure out the jitter, one or two are pretty ‘out there’ but plausible all the same:

Something else that jumped to mind was whether you are using image stabilisation on the Canon or not. There’s are reasons I can think of why it may be creating this unwanted effect by being either on or off. It would be worth trying to shoot some footage to test this. If image stabilisation is on – which it probably may be – what could happen is that the camera could be trying to compensate for very regular ‘noise’ on the y axis (i.e. the steps of the stepper motor), since image stabilisation is designed to reduce unwanted movements produced from organic, irregular human movements, it may not be very sucessful at reducing movement from the revolve and might actually magnify or even be responsible for some of stuttering.

Another possibility is that the stuttering may be a product of constructive interference between the stepping frequency of the motor and the framerate of the camera – the two frequencies could be out of phase in a way that produces unwanted motion in the video footage. As far as I know, the Canon shoots progressive frames at a fixed framerate of 30 FPS. Progressive meaning that each frame is captured by the CCD and stored in one pass, as opposed to interlaced where each frame is captured as two fields and mixed together alternatly during playback – resulting in 60 half frames. If this is happening, a possible (hack) solution might be to very slightly change the speed of the revolve, plus or minus a 1% perhaps. If you do try this, make sure to note the exact speed you used for each shot, as syncing up the video upon playback will rely on knowing this speed.

As I am sure you are already aware, video compression adds another layer of complexity to figuring out the cause of certain video artifacts, so too do the physical attributes of the camera. The Canon 5D mkii seems to have issues with what is known as rolling shutter, where unwanted movement is untroduced during panning shots, it may be more apparent with a motorized panning head.

http://www.crunchgear.com/2008/09/27/canon-5d-mark-ii-exhibits-jello-effect-not-as-bad-as-d90/

there seem to be some solutions to reducing or removing this in-camera artifact online

http://vimeo.com/4987665

Compression could definitely be an issue with this problem you are having – especially since you have noticed a reduction when using a different compression type. The Canon 5D shoots video natively in H264, that while being a sophisticated and very high quality codec, is a ‘lossy’ compression technique that uses intra-frame compression as part of its suite of compression tools. Intraframe compression uses data from preceding and/or following frames to apply compression to the current frame. This allows for more intelligent and usually higher compression ratios but may also discard information that is crucial to particular types of motion, and panning seems to be one of these.

http://www.dvinfo.net/forum/canon-eos-5d-mk-ii-hd/288686-stutter-jitters-whilst-panning.html

One test you could try would be to shoot in 720P 60FPS – this will double the number of frames shot which, while reducing the resolution of the image, will increase the temporal resolution which is important to capturing motion. The footage could then be pulled down to 24 or 25 fps in post-production for playback purposes if needs be.

machine design, motion control, moco, stepper motor, motor controller, mechanical design, machining, visual arts

Since the projector was to project a circular image onto a circular screen I could turn the projector on it’s side without any issue. This was the starting point. I cut some sheet metal to match the base of the projector with some mounting holes. The sheet metal would act as a chassis of sorts, for attaching the reels and a mount to and also to hide the ugly plastic underbelly.

The reels were made of plastic reels used as packaging for rope lighting which I procured from a friend. The photos pretty much tell the rest of the story from here – they may be useful for someone trying to do something similar.

The combination of flickering light from the projector, a fake lens barrel and the turning reels made a pretty convincing film projector to the unobservant eye and the drunk (it was in a nightclub after all). I’ve not included final images as they are branded almost out of existence.

This was my first time to use dome projection. It was quite tricky. It looked great in the end but as always, I wish I had more time to tweak the video design. This production was for secondary schools and John wanted to create an immersive environment to stage it – in most schools, the only place big enough to stage something is the gym. Gyms are not suited to staging shows – very bright, painted white, nasty acoustics etc. So the idea of a blacked out dome was brilliant – quick to set up, potentially big enough for a decent audience and most importantly would create an intimate, controllable play space. Domes also have a lot of surface area to project onto ;)

John wanted me help convey a number of things – the sense of driving at speed, doing doughnuts in a car, an abstract dance sequence and dreamy out of body sequences. There was also a need for the projections to light the show with general washes and animated ambiance. I was originally going to shoot footage for this with a fisheye lens but decided that realism would have been too distracting, amongst other things, so I generated everything in 3D Studio and After Effects from stills that I shot. Most of the sequences are exterior-night and darkly atmospheric. I used heavy motion blur, depth of field and muted colour. Each sequence began as a circular frame, where, if you imagine, the outside ring would be the bottom of the image in the dome and the centre of the circle would be centre and tallest point of the dome – VERY tricky working like this.

These circular sequences then went though a bunch of processes to prepare them for dome projection. I used image sequences – distorted the image using a fisheye mesh (all the sequences were larger to allow for the distortion), then a piece of software called TGAWarp by Paul Bourke to pre-warp the images in a 4:3 ratio. Using 4:3 makes better use of the available resolution when using the projection technique I was using.

There are lots of ways to project onto a dome – from the outside with multiple projectors, from the inside with multiple projectors, from the inside – in the centre – with a single projector etc. but for all sorts of reasons – especially since the entire floor was needed either seating or stage – there was only one suitable method – using a spherical mirror. This method was also developed by Paul Bourke and everything you need to know about using this technique as well as developing content for dome projection is on his website.

Friday I’m in Love by The Cure is on the radio yet it’s Monday today – this is great because i HATE when DJs play this on Friday – YAWN. Anyway, at the same time, i’m perusing through one of my all new favourite websites. Sweet for so many reasons, firstly it’s not about anything I’ve been recently reading too much of (the weather, irish politics, film listings & reviews), but it’s about things you need to make other things with, namely mechanisms and machines. Other reasons include – beautiful design – graphical, layout and usability, gorgeous renderings of objects – that are so consistent, clear and simple that it’s a major credit to whoever is responsible. The search and ‘drill-down’ features are so good that you can find the part you need within seconds. Not only this, but at almost every point there are clearer graphics and lots of information on parts, their features and how to select them.

Even if you are not into mechanical engineering/fabrication/robotics etc., you should take a look at this site, if not only to get an idea of  how many mechanical parts there are out there, being mass produced to very high standards that are behind the scenes of most things we use today (they boast 480,000 products – jayziz). But also, hopefully it will demonstrate how pleasurable it can be to use a website that’s as well made as anything it’s trying to sell to you.

McMaster-Carr

Alas, it’s US based and they don’t deliver to Europe. However, a bit of sniffing around dug up this crowd in the UK (GBHTechnical) who claim to import the McMaster Carr range of products.

Freefall is currently on tour, we did two dates in the New Plays from Europe festival in Wiesbaden, Germany http://www.newplays.de in June. Freefall will in The Traverse in Edinburgh for the Edinburgh Fringe festival. Tour also takes in a bunch of theatres around Ireland as well as the Cervantino Festival in Mexico. Check out The Corn Exchange Theatre company’s website for more info on dates etc.

GAF TV (Galway Arts Festival TV) has a little segment on the video design for Freefall. Have a look here.

16 – 19 JUN 2010 upstairs at Project Arts Centre.

By Dylan Tighe in association with Blanchardstown Traveller Development Group and Irish Traveller Movement.  Set design by Alyson Cummins, Lighting design by Sinead McKenna, music and sound design by Sean Óg, video design by Jack Phelan)

(from Project Arts Centre website…)

Set on a present day halting site The Trailer of Bridget Dinnigan follows matriarch Bridget and her family in the period after her husband’s death. Fiercely protective, Bridget will stop at nothing to ensure that her family’s reputation remains intact. Tensions rise when the eldest daughter announces her engagement and family secrets are revealed, which lead to tragic consequences.

This contemporary adaptation of the Spanish classic The House of Bernarda Alba, by Federico García Lorca, is the result of two years of research and collaboration between theatre-maker/writer Dylan Tighe, Traveller activist Catherine Joyce and eleven women from the Blanchardstown Traveller Development Group.