Hi all...

I've been building a mirror rig using My Sony EX1 and Convergent Design's EX3, for the purpose of testing and product feedback for the nano3D. We first put together a side-by-side rig, shot some real world projects, and quickly learned the limitations in terms of I.A. and stereo space compared to a mirror rig.

I thought I'd share some of the process, both in design and construction, for all that are interested. Not everyone will want to build their own rig, but it's an interesting process and quite a learning tool for the stereographer in training.

The first step was to determine the major components and parameters;

1.) Zero I.A. up to about 5" of I.A. at full wide angle (64.7 degrees Horizontal FOV) on the EX zooms was important. This determined the size and shape of the mirror and in fact, the whole rig.

2.) I also wanted the I.A. to be evenly split between the cameras, centered over the tripod pan. Most rigs just move one camera, so any pan tends to occur under one eye, with the other eye pivoting around that point. Not very natural, IMO.

3.) I also wanted an "over" rig, with the second camera shooting down. This allows for tripod tilts and jib operations easier than the "under" rig style. Of course CMOS skew needs to be accounted for, and that means that the over camera is orientated so that the tripod base faces out from the rig.

Nothing beats the real thing, so before heading into the computer to design the rig, I mocked up the cameras in real space to get a feel for the volume and see what issues I might face. Here are some alignment tests during the design process;

http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_rig_01.jpg
http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_rig_03.jpg
http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_rig_08.jpg

As an aid to alignment, I built some foam core lens hood extenders that allowed optical axis placement and a visual check for alignment, as you can see in the photos. Since then, I learned that there's an actual PL mount tool similar to this, that you can use on "real" cameras... nice.

More to come...

Regards,

Jim Arthurs

Next in the process was selection of materials. I'd seen pictures of the 3D Film Factory rigs...

3D CAMERA RIGS (http://www.3dfilmfactory.com/index.php?option=com_content&view=article&id=52&Itemid=76)

...and noticed that they were built, for the most part, with components from the 80/20 company...

80/20® Inc. - The Industrial Erector Set� (http://www.8020.net/)

So, why re-invent the wheel? I did take a number of design changes, where I thought the Film Factory rig was lacking, beefing up the main assembly and allowing for my dual camera I.A. adjustment.

While the side-by-side rig I built for Convergent Design had toe-in, here on the mirror rig I made the command design to keep everything parallel, and rely on the nano3D's ability to preview horizontal adjustments. Since the nano3D also allows for image flip and flop, can preview anaglyph, you can pretty much eliminate all the billions of black boxes needed to preview your stereo in the field.

In my 3D program of choice, Lightwave, I designed the rig and created a cut and part list for the 80/20 materials...

http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_layout4.jpg

Navigating the 80//20 catalog and creating an order is a bit like learning a new language, but soon I had a nice package of materials on my workbench, all cut and tapped, ready for assembly...

http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_mirror_rig_01.jpg

While it would take some time to get everything really put together, within an hour I was looking at this...

http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_mirror_rig_03.jpg

More to come....

Jim Arthurs

The big problem with the Sony EX1/EX3 is the tripod screw area... it's horrible. The entire bulk of the camera depends on a tiny metal plate less than 1.25" by 1", held to the bottom of the camera by 4 tiny screws. On top of that, the bottoms of the cameras are curved and non-planar, an attachment nightmare.

There are third party options, various base plates and the like, but I wanted something better, something actually registered so that you could remove and return the cameras to the mounts and not have to re-align.

The solution that came to mind was to take a pair of Bogen 357 release adapters and modify the camera plates with a custom molded base. This was going to be a world of hurt in terms of effort and time, but I felt it would pay-off.

So, step one; pull RTV silicon molds from the bottoms of each camera.

http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_rig_04.jpg
http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_rig_05.jpg
http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_rig_02.jpg

Next, pull male copies from the molds, using a mineral filled urethane plastic..

http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_rig_09.jpg

I then filled in all the tiny details and screw recesses on the males, creating a smooth "plug" for casting the final camera seats.

Next I machined up some aluminum riser plates to compensate for the different optical axis heights between the two cameras;

http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_rig_12.jpg
http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_rig_10.jpg

Now I was ready to cast the custom seats in plastic right onto the modified plates/risers...

http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_rig_13.jpg

Giving me these...

http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_rig_14.jpg

After they are sanded down, and all the areas where buttons on the cameras might be covered are revealed, they will be ready to work. A completely custom solution with precise registration.

Oh, did I mention that the EX3 actually tilted DOWN a couple degrees in normal mounting, and wasn't perfectly perpendicular? I had to compensate for that in the mount as well with a few shims under the riser... good times...

More to come...

Jim Arthurs

Next up is the mirror and mirror frame assembly. My mirror needed to be 10" by 18.5" to accommodate the full wide angle of the EX1/EX3 stock lens, and allow about 5" of I.A.

I got the 50/50 mirror from these folks;

Stereoscopic Mirror Manufacturing (http://www.stereoscopicmirrors.com/3d.htm)

Custom cut, it was about $210 US... I don't want to break it! I will be using a piece of plexi as a stand-in until the rig is finished. And yes, the upper camera will have a fail safe to keep it from sliding down and crashing into the mirror.

I puzzled over the mirror mounting for some time. I didn't want any stress on the mirror, and I wanted it supported as much as possible. I took aluminum channel guide designed to fit around 1/4" thick panels and bent a three sided frame out of it, with the corners re-enforced with gussets.

http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_rig_16.jpg

The inside of the channel will be lined with 1/16" sponge neoprene on all three surfaces to cushion the glass. Did I mention I don't want to break it?

To mount the frame to the rig, I'm machining some attachment posts that will allow the frame to be adjusted up or down, and will add some rigidity to the assembly. Here's one in progress on the mill...

http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_rig_17.jpg

More to come...

Jim Arthurs

Thank you Jim! Please keep posting
Cheers

Great Posts!

We have been using a 3D Film Factory Rig for the last 4-5 months, so its fascinating to see this approach.
Thanks Jim,

Bwe

Hi all... finished the fitting and sanding of the camera saddles and did all the necessary opening up of areas for access to all controls and ports. Used my big 10" disk sander and a dremel tool for the close work. I still need some fine sanding and some spot putty, maybe a paint job.

http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_rig_18.jpg
http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_rig_19.jpg
http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_rig_20.jpg

This was the moment of truth on quite a series of steps and labor that I outlined earlier. Wow, this WORKS. Absolutely no play in the cameras, so solid and rigid that it's a bit scary. Perfect registration, and I feel comfortable removing the cameras and putting them back and not having to worry about a re-alignment.

Some manufacturer needs to get on mass producing this sort of cradle/saddle for the EX1 and the EX3. I know I'll use them for my normal day to day tripod operations as well.

More to come...

Jim Arthurs

Okay, I've got the mirror frame finished, save for the neoprene. I did have to make a second mirror frame, as my first one was about .25" too wide. Operator error, measure twice, cut once, etc.

The pivot supports turned out great, no chance of stressing the mirror and they tighten down real well... plenty of adjustment, the frame can be moved independently on the supports up or down, the support mounts can be moved forward or back, and shimmed higher if necessary.

http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_rig_21.jpg
http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_rig_22.jpg
http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_rig_23.jpg

As an overview, here's the rig at the moment, I just need to finish the camera platforms (the EX3 platform is finished) and I'll be ready to give it a go.

http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_rig_24.jpg
http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_rig_25.jpg

Oh, I still need to find the balance point for the tripod mount, but I'll wait until I can load up the rig with the cameras and all accessories before doing that.

I'm ordering up some more small items for the finish. Boy, these pictures remind me I need to do a full workshop clean-up soon!

More to come...

Jim Arthurs

Thanks everyone for the feedback on and off the forum!


We have been using a 3D Film Factory Rig for the last 4-5 months, so its fascinating to see this approach.
Thanks Jim,

Hi Bwe, I'd love to hear about your experience with the Film Factory Rig, and any comments you might have on what works well, and what doesn't. I'm sure I'm doing things differently in certain areas, and it's never too late to change things!

One thing I would be interested in knowing is if you're able to shoot at more than one focal length, or how difficult it is to re-adjust if you do change zoom.

I'm optimizing my rig for the EX1/EX3 combo, but I'm pretty sure a couple of RED's could fit on it as well with just a swap out of the camera support posts.

I do now have a great appreciation for folks that want to manufacture a rig, it's no small undertaking, and something I would never want to do.

Regards,

Jim Arthurs

Jim,

You are having way too much fun! The cradles look great, when can I get a pair?

Have you seen these for alignment: adjustable instrument & camera mount: Huber Industries (http://www.hubermounts.com/300d.htm) I'm thinking about some uProcessor driven stepper motors to drive the screws.

Brian

Well funnily enough I have been using the EX1/EX3 combo aswell, and for the most part it is working well now. Initially it was alot of work to figure out the best way to put it together.

We have the Indie rig, and the first thing we realised was that we couldn't have the ex3 as the (top,left,moving) camera. It was just a bit too heavy for the mount so it wouldn't sit at 90 degrees, im sure with some stronger mounts it would be ok, I just havent taken the next step yet.

Then to squeeze the cameras into the rig so they could line up we pulled off a few of the crossbars, the handle/controls of the cameras initially would just overlap.

http://www.naluproductions.com/downloads/indie_rig.jpg

Apologies im not the well versed on the materials/building side of things.

Before any shoot I use a laser level to align everything, while monitoring the picture on a laptop.

http://www.naluproductions.com/downloads/indie_laser01.jpg
http://www.naluproductions.com/downloads/indie_laser02.jpg

Its usually right to go from then on, changing focal length is a bit of a pain, but just having a checklist of things to run through each time helps. We actually plan alot of shots either full wide or full zoom, and have those two positions marked out on the rig so it can quickly be lined up. Don't have a zoom system yet (asking santa for that one), and sticking to shooting parallel so any small adjustments/cropping I do in post, which is inevitable anyway.

Love your mounts and the position of the lower camera on your rig, just having the ability to move both cameras horizontally is something I really wish we had. Also having just one point to move pieces would be great.

eg. one spot to move mirror forward/back, one spot to raise the left camera up and down, rather than 4-8 screws each time :)

Bit long winded, apologies. Any specific questions let me know :)
Big grats on the rig too, its looking great.

Brendan

The use of the laser level is interesting. That it gives you a cross hatch pattern is really nice. Can you share where one obtains this laser tool?

The laser is a GREAT idea, THANKS Bwe, and it gave me an idea to do something similar... I've got a shop laser that I'm mounting to fit the front of the mirror box so that it's an all in one solution with registration to the rig... That way you just clip it on the front, and you can align without having to set up an external unit.

Here's the laser I'm using, it has a precise shaft and can fit into a jig with good registration...

LittleMachineShop.com - Edge and Center Finder, Laser 3/8" Shank (http://www.littlemachineshop.com/products/product_view.php?ProductID=2604&category=)

Regards,

Jim Arthurs

Not being a wood worker or machine shop guy I'm somewhat confused by your terminology here. Does this laser unit that you've linked to provide the cross-hatch type of pattern we see in the above photos? Where are you mounting it to obtain a perfect centered spot?

Not being a wood worker or machine shop guy I'm somewhat confused by your terminology here. Does this laser unit that you've linked to provide the cross-hatch type of pattern we see in the above photos? Where are you mounting it to obtain a perfect centered spot?


Hi Bruce, this video should explain the function of the laser in the shop...

Laser Center/Edge Finder In Action (http://lasercenteredgefinder.com/video1.html)

It doesn't make a cross-hatch pattern, just a fine dot. It would be mounted at lens center on a support at the front of the mirror box, dead center (adjustable up or down). I would then put paper cross-hair patterns on the lens fronts and align from there... I'll post pictures when I get to that point to make it more clear...

Jim A.

Thanks for the link to the video, it is easy to understand how to use it from the video.

I'm interested in the cross hatch pattern that Bwe shows in his two pics from the post above;

http://www.naluproductions.com/downl...ie_laser01.jpg
http://www.naluproductions.com/downl...ie_laser02.jpg

What laser was used, how did he achieve the cross hatch, and where and how was the laser mounted in front of the rig?

Hey Bruce,

Sorry for the delay, was enjoying a weekend off work for a change!

Here is a picture (pic 1) of the laser level box, the tech guys at work sorted it for me, so I can't really give you specifics on it, hopefully this helps in tracking one down in the US. They just got it from a hardware store (Bunnings in Australia) over here.

http://www.naluproductions.com/downloads/laser_level.jpg
http://www.naluproductions.com/downloads/IMG_0079A.jpg

The real beauty is it auto levels, so just mount it in front of the rig (see 2nd pic) and it really helps initial alignment and checking the rig. You also get a nice flare in the lens which you can line up in the viewfinders too.

If you need any more specifics let me know :)

Brendan~

Thanks for the additional picture. I found a cross hatch laser at my local hardware store so I'll be experimenting with it later this week.

Bwe, if you want to compare 3DFF rig notes, contact me off list and I'll be happy to share my tips and tricks with you since I've been using the rig quite a lot since January of this year.


Bruce Schultz
herrschultz@usa.net

Got brave enough to test the mirror in the frame, a very nice fit. Here's a couple shots of the 1/16" sponge neoprene to cushion the mirror...

http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_rig_31.jpg
http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_rig_32.jpg

And here's the cameras in position for the first time!

http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_rig_33.jpg
http://ftp.datausa.com/imageshoppe/images/MIRROR_RIG/EX1_EX3_rig_27.jpg

With a few pieces of black show card installed to block light around the mirror box, I think it's time for some tests...

Jim Arthurs

Okay, I've got the worst talent in front of the rig possible; myself. Yet here is the very first series of tests from the rig. I've varied the inter-axial settings on a room sized scene, shot parallel, and converged in post (Sony Vegas 10) to test things out. At this point, not even a tripod mount, it's simply setting on a table.

YouTube - STEREO MIRROR RIG "FIRST LIGHT" (http://www.youtube.com/watch?v=r_w0KEf5TPU)

Actually, a pretty useful tests for anybody to do or see... we could use more stereo examples like this posted. Hint, hint...

Wait a minute! I forgot the most important part... the darn thing actually works!

Jim Arthurs

Looking good, but your camera heights are miss matched. While you have matched L/R images on the screen plane, distant and near objects are shifting either up or down giving you some vertical disparity, particularly noticeable with objects in the background. This problem is a difficult one (and common one) as you can adjust out the error using mirror or camera tilt for any given distance, but at other distances you will have errors. Getting everything equal and exactly on the optical axis is tricky. Even some of the high end rigs have trouble with this.

There also appears to be a rotational difference between the left and right cameras. as objects on the left of frame are aligned better than the right.

I strongly recommend the use of a scene with much greater depth for alignment tests as errors become much more obvious when there is more depth. When the errors are easier to see, they are easier to resolve. I think part of your problem is because the mirror pivot point is not aligned with the cameras optical axis so when you tilt the mirror you also move the virtual height of the reflected camera so you end up in a vicious circle where you adjust the tilt to get zero vertical disparity at the screen plane but the tilt moves the virtual hight with throws out near and distant disparity. Ideally you need the cameras at exactly the same hight, centred on the mirrors optical and rotational axis, then changing the mirror tilt will not affect near and distant disparity.

Still a good job, building a mirror rig is one thing, getting everything centred on the optical axis correctly is another. You look to be pretty close. The really hard bit comes when you start to converge the cameras as any tilt or roll of the converging camera, it's mounting, the lens or the sensor within the camera will translate to differing amounts of camera tilt for every convergence setting. It's enough to drive you mad trying to work out where the problem is.

My Hurricane-Rig design had a problem where the optical axis was changing by around 0.2 degrees as you wound the camera from zero IA and 120mm IA. It took an age to find what was causing the problem. In the end we found that machining out a small area of metal to make the rigs reference plate lighter was causing the 12mm thick plate to distort very slightly in the opposite direction to the machined area. We only discovered this when we noticed the machined plate "ringed" when placed on a surface plate (perfectly flat 5" thick slab of marble) as opposed to making a flat sound. We are now skimming the reference plates after machining and every reference plate will be checked for flatness. Even anodising parts has to be done in a special way to ensure we don't get any distortion.

I'm not sure about neoprene for the mirror surround. Its a tricky one and different people have different views on this. One issue you do need to consider is how the mirror will respond to sound. If the mirror is not mounted rigidly enough it will act as a large microphone and vibrate in noisy environments. Mount it too tightly and distortions will be introduced as the frame expands and contracts with temperature. It needs to be fairly solidly mounted, with no pinch points (which introduce all sorts of weird distortions to the light passing through the glass) but the frame needs to be able to expand and contract without stressing the mirror.

What I'd like to know is how you manage to hold the EX-3 pointing down. The EX-3 has its tripod mount attached to the camera on a thin plate held to the body of the camera by four tiny screws. I would be so nervous that gravity would break the camera away from the plate and that I would lose a very expensive (to me) camera as well as the mirror rig, that I could not even concentrate on filming.

Or is it all holding together stronger than it looks?

What I'd like to know is how you manage to hold the EX-3 pointing down. The EX-3 has its tripod mount attached to the camera on a thin plate held to the body of the camera by four tiny screws. I would be so nervous that gravity would break the camera away from the plate and that I would lose a very expensive (to me) camera as well as the mirror rig, that I could not even concentrate on filming.

Or is it all holding together stronger than it looks?

Hi Adam, this was a major design feature in my rig... check out the early posts in this thread. I've made custom resin saddles that fit the curved bottoms of these cameras, relieving all the rotational and other stresses on the screws. They also account for the optical axis differences between the EX1 and the EX3, so the lens centers are at the same height. I spent MUCH time on this. The cameras are held absolutely solid and rigid.

I now use these cradles even when using the cameras as normal on a tripod, it's that big of an improvement over simply screwing them down. A manufacturer should really jump on this and provide them for the EX cameras.

FYI, I've got the EX1 (smaller and lighter) hanging down not the EX3...

Looking good, but your camera heights are miss matched.

Thanks Alister, I really appreciate your input. Your rig will largely make these sort of mirror-rig DIY projects moot, and I look forward to seeing your rig at NAB in person. I've got a great amount of respect for anyone attempting to not only build a one-off, but to actually mass-produce their design. Also it gives great hope hearing your own personal trials and tribulations with the process.

It's important to know that my rig is a one trick pony, designed to use the EX1/EX3 exclusively, probably living its life at full wide on the zoom, acting as a test bed for HIT and other image processing functions in-house with Convergent Design.

I'm aware of these alignment issues, and I've got some tweaking ahead, so perhaps posting anything image-wise was premature. Call it the excitement of the moment in seeing any footage with tiny inter-axial!

The cameras are on posts that are machined to custom heights for each camera. I haven't had the time to machine in the exact height yet. And the rig had to be dis-mantled for anodizing, and I've left all the adjustments until after it's put back together. Your tips are wonderful and will aid in that alignment. Thank you.


I'm not sure about neoprene for the mirror surround. Its a tricky one and different people have different views on this.

I appreciate knowing these views, as this is simply my best guest approach without benefit of any industry wisdom! I simply have no idea of how people are securing the mirror in the real world. I really need to take one of those weekend seminars so popular now and get up to speed with how the real rigs work.

Anyway, It's hard to display the exact "fit", but here's my description of the fit; The mirror slides into the frame with no binding, but no real amount of play either. The frame channel is 1/4", with 1/16" neoprene above, below and to the side of the 1/8" thick mirror.

I've not had the chance to lay eyes on a "real" rig, but I think I'm pretty close to "low budget ideal" with this design. The mirror is cushioned, but not compressed, and floats in the frame, with hopefully any external forces acting on the frame and not directly on the mirror. Of course testing is required, and will reveal all the design flaws.

Regards,

Jim A.

Wow, you're really good! A very impressive solution. Thanks for sharing it, even if it is way over my head (I am a software guy, not a hardware guy). And yes, I hope someone will start manufacturing your solution and even pays you for the idea!

When you set your camera heights be aware that the orientation of the camera (ie vertical or horizontal) causes the image stabiliser element in the lens to shift (even when "Off") which moves the optical axis of the camera up and down. It's one of the many difficulties added when you use lower cost cameras. The zooms also wander up and down a lot at different focal lengths.

Find a top quality anodiser. The preparation process can cause warping and any variation in the thickness of the anodising can cause the parts to distort by small amounts.

When you set your camera heights be aware that the orientation of the camera (ie vertical or horizontal) causes the image stabiliser element in the lens to shift (even when "Off") which moves the optical axis of the camera up and down. It's one of the many difficulties added when you use lower cost cameras. The zooms also wander up and down a lot at different focal lengths.

Yikes, I did not know that about the image stabilizer. Nor would I have ever found out in this particular case, as the measurements for the milling adjustments to the standoff height would have taken place while the EX1 was in vertical position pointing down.

I had previously charted the the zoom center wandering of the EX3 compared to the EX1 (at least for our samples). Here's what that looks like over the full zoom range (note, the zoom speed is not matched between cameras)...

http://ftp.datausa.com/imageshoppe/outgoing/nano3D/EX1_EX3_zoom_center.mov

I was going to plot the zoom range offsets out at various focal lengths, but that became moot when I decided that the two cameras were going to spend their time at full wide on the rig, with all the adjustments and tweaks aimed at making that focal length the most perfect match I can get.

Thanks again, Alistar! I'll soon discover how much damage was done by the anodizing, as the parts are all finished and prepped, in a pile, waiting to be put back together this weekend...

Your video is a good example of zoom centring errors. The EX's are particularly bad, which is why at this point in time we are not doing a dual zoom control. It gets worse when the camera orientation is different. The most troublesome bit is that initial dip that many of them seem to do around 10mm to 20mm which is in the "useful" part of the zoom range from a 3D perspective.

Have fun building up your rig. I look forward to the next installment.

Thank you Jim for taking the time to give us a detailed DIY guide. Would really love to know how the final rig turned out!