Why is a 3D rig expensive?

[David Quinn Carder]

If I understand correctly, all you need is two cameras with lenses positioned like our eyes positioned on our head, both pointing straight forward; also, the ability to sync the two cameras. I read something about "convergence" in a thread here and that's what threw me off . . . maybe I'm missing something?

Apologies if this has been covered already.

[Eren Ozkural]

The RED 3D rig should be rather cheaper than other 3D rigs because it's designed for 1/2 types of cameras only, it looks like a parallel only set up and RED are very aggressive on their pricing anyway.

The reason why a lot of other rigs cost money is if they're beamsplitter rigs. Normally cameras are too large to use attache side by side...the bodies are too large to simulate the 2.5 inch distance between the average human pair of eyes.

To combat this the rigs place one camera above, pointed down at a mirror tha splits the light ont the two cameras. The bodies can be aligned closer together as they're not clashing for space.

The engineering and materials that go into this must be quite costly.

I'm sure that someone here like Mark can clarify better than I can.

[Michael Hastings]

David:

It depends on what you want to do.

The issue that comes up is that you need to have very close intraocular distances to shoot things reasonably close. The rule of thumb is to have your subject distance about 30 times the intraocular distance. So for side by side cameras with lenses or body width that are about 3" the closest you can get them is a 3" intraocular distance which dictates a 90" or about 7.5 foot subject distance. The minimum R1 side by side is about 5.2 inches so 156 inches or 13 feet which is not a very normal shooting distance for a lot of things.

Beamsplitter rigs are a solution for small intraocular distances with big cameras.

With that said, my company has been working with some Canon HFS100 cameras which allow about 2.3 to 2.5 inch intraocular and we are able to do some pretty cool things with them. They are very useful for a lot of things and certainly help you learn and understand some of the issues. We set this up primarily for underwater but are planning to make some mounts and brackets for regular use that would cost just a couple hundred dollars (You need to make sure that the cameras are very square and solid or you create major headaches for editing (and viewing!).

Since the cameras (full 1080P 24Mbps H.264) are about $900 apiece you can get into it for a little over $2K. And for super cheap we are playing with some Sony "Webby" cameras since they allow extremely small intraocular and prices for two cameras and a 3D mount for less than $700!

So 3D doesn't have to be expensive, and you can do a lot, but full featured 3D with a lot of creative capability and flexibility probably will be expensive for awhile.

But the trend is in the right direction. The fact that we can get two full 1080P camcorders for $1800 is the first step and if/when perceived market volume is great enough for the video camera manufacturers to incorporate stereo optics with intraocular manipulation there is no reason that that couldn't be done for a few thousand dollars - and a true 1080P/2K full featured stereo camera could be had for what we used to pay for an HVX200.

And Red might be the company that decides to do that...

[Jeff Coatney]

When we humans look at something close to us, like a foot or two away from our faces, our eyes actually cross to keep that object centered and focused in our field of view. When we cross our eyes, like when we're making a goofy face or something, you get two discreet views of the world super-imposed on each other. Normally, our eyes sit parallel to each other when we look at subjects on the horizon. When the subject moves closer to us, our eyes begin to cross ever so subtly to maintain the subject in our field of view and in focus. This "eye-crossing" is called convergence.

There's is absolutely no variability in a 3D rig except for the angle at which the two cameras converge. The inter-occular distance is always 65mm. It doesn't matter which format of camera you use, from IMAX to super8mm and everything in between, the inter-occular distance is 65mm because that matches the average position of the left and right human eye relative to each other.

The convergence angle is the degree to which the eyes cross. In a 3D rig, you can have any amount of convergence from 0 (where both cameras are facing forward, in parallel) to about 20 degrees (each camera, pointing towards the other one in a crossed orientation at 10 degrees, giving you a net 20 degree effect or a convergence angle of 20 degrees).

Deviating from these values can induce eyestrain, headaches, vertigo and even a violent, intense desire to look away on the part of the viewer.

[Michael Hastings]

There's is absolutely no variability in a 3D rig except for the angle at which the two cameras converge. The inter-occular distance is always 65mm. It doesn't matter which format of camera you use, from IMAX to super8mm and everything in between, the inter-occular distance is 65mm because that matches the average position of the left and right human eye relative to each other.

The convergence angle is the degree to which the eyes cross. In a 3D rig, you can have any amount of convergence from 0 (where both cameras are facing forward, in parallel) to about 20 degrees (each camera, pointing towards the other one in a crossed orientation at 10 degrees, giving you a net 20 degree effect or a convergence angle of 20 degrees).

I'm going to disagree with you there. The whole point of a beamsplitter rig is to allow the lenses to achieve an intraocular less than would be physically possible with the size of the camera/lenses. Again, I am just learning this stuff but about 99.9 percent positive that I am correct on this score.

One of the big things in underwater is to do macro shooting and that is where the beamsplitter excels because you can actually achieve zero intraocular (obviously not a lot of point in actually getting to zero but in practice you would use very narrow (sub 1 or even .5 inch).

[Joey R.]

If you have to ask....

In all seriousness yes, you can absolutely shoot 3D with two cameras, a couple of nails, a 2X4 and some shoe laces and you may even get it to not suck.

We built a beamsplitter rig used by Geoff Boyle for Dark Country. It was the collaborative efforts of a mechanical engineer and a machinist and it took just over a week to create. It was inexpensive and it worked fine. There were a few more made and they have been out on productions ever since.

So lets first look at what makes it cheap:
• Only one camera can be used (SI2K)
• Only one glass type (C-mount primes)
• No convergence
• Small interocular travel
• ~15lbs with cameras
• Low overhead
• Relatively short machining time

So what makes a GOOD rig expensive?
• Convertible from beamsplitter to side-by-side
• Able to mount MANY camera types
• Hard-core rigidity making it damn near impossible to make the two cameras move when doing something as simple as sweeps and moving from a dolly to a crane.
• Alignment that doesn't change with every camera movement
• Motorizing the I/O and C movements
• Having a wireless controller that controls said I/O and C movements at distances as great as 1500ft in both wired and wireless configurations
• Having an alignment process that takes anywhere from seconds to minutes (how fast can you turn knobs?)
• Software that calculates the correct convergence tangent relative to the I/O
• Prototype planning for two smaller sizes
• etc etc etc

Now of course add on to that 6 CNC machines running non-stop, a crew of over 20, a beta testing regimen that gathers hundreds and hundreds of hours of testing footage and data. A few prototypes builds, marketing blah, trade shows blah, advertising blah.

Its expensive and time consuming unfortunately. But when you are in your post facility and you see the type of stereo you get at the end of the day, our goal is that you are pretty happy.

[David Quinn Carder]

When we humans look at something close to us, like a foot or two away from our faces, our eyes actually cross to keep that object centered and focused in our field of view. When we cross our eyes, like when we're making a goofy face or something, you get two discreet views of the world super-imposed on each other. Normally, our eyes sit parallel to each other when we look at subjects on the horizon. When the subject moves closer to us, our eyes begin to cross ever so subtly to maintain the subject in our field of view and in focus. This "eye-crossing" is called convergence.

There's is absolutely no variability in a 3D rig except for the angle at which the two cameras converge. The inter-occular distance is always 65mm. It doesn't matter which format of camera you use, from IMAX to super8mm and everything in between, the inter-occular distance is 65mm because that matches the average position of the left and right human eye relative to each other.

The convergence angle is the degree to which the eyes cross. In a 3D rig, you can have any amount of convergence from 0 (where both cameras are facing forward, in parallel) to about 20 degrees (each camera, pointing towards the other one in a crossed orientation at 10 degrees, giving you a net 20 degree effect or a convergence angle of 20 degrees).

Deviating from these values can induce eyestrain, headaches, vertigo and even a violent, intense desire to look away on the part of the viewer.

Thank you all for your answers, but Jeff, this is what I was looking for. I understood that eyes converged but did not know it was necessary for cameras as well. This kind of shoots down my hopes of run-and-gun 3D shooting. If I understand correctly, this means that it is intrinsically impossible to create 3D video that allows the viewer to focus on whatever they want in the image, even if the depth of field is deep, because of the convergence factor required when dealing with nearby subjects.

Is this correct?

[Ryan S]

Great post Joey, very informative! Thanks.

[KETCH ROSSi]

If you have to ask....

In all seriousness yes, you can absolutely shoot 3D with two cameras, a couple of nails, a 2X4 and some shoe laces and you may even get it to not suck.

We built a beamsplitter rig used by Geoff Boyle for Dark Country. It was the collaborative efforts of a mechanical engineer and a machinist and it took just over a week to create. It was inexpensive and it worked fine. There were a few more made and they have been out on productions ever since.

So lets first look at what makes it cheap:
• Only one camera can be used (SI2K)
• Only one glass type (C-mount primes)
• No convergence
• Small interocular travel
• ~15lbs with cameras
• Low overhead
• Relatively short machining time

So what makes a GOOD rig expensive?
• Convertible from beamsplitter to side-by-side
• Able to mount MANY camera types
• Hard-core rigidity making it damn near impossible to make the two cameras move when doing something as simple as sweeps and moving from a dolly to a crane.
• Alignment that doesn't change with every camera movement
• Motorizing the I/O and C movements
• Having a wireless controller that controls said I/O and C movements at distances as great as 1500ft in both wired and wireless configurations
• Having an alignment process that takes anywhere from seconds to minutes (how fast can you turn knobs?)
• Software that calculates the correct convergence tangent relative to the I/O
• Prototype planning for two smaller sizes
• etc etc etc

Now of course add on to that 6 CNC machines running non-stop, a crew of over 20, a beta testing regimen that gathers hundreds and hundreds of hours of testing footage and data. A few prototypes builds, marketing blah, trade shows blah, advertising blah.

Its expensive and time consuming unfortunately. But when you are in your post facility and you see the type of stereo you get at the end of the day, our goal is that you are pretty happy.

This is why I have been doing business with ET for about two years now, and why I'll be there next week to see the rigs.

Quality of the Rigs built is not all, they must also have Precise and full control of both camera in absolute Sync, and all controls must allow for a simple use in the complexity of the set up, making it as easy as possible for its operators to pay more attention to the shot, instead of the rig, and even if they are now more and more emerging 3D rigs, only few, and only few are worth the prince, as just about any good engineer and or machinist can build one, but only few can master the electronics that go with in order to fully control all aspects of the otherwise incredibly difficult set up that a S3D set up presents, and this is why the old 3D was just not good, they didn't have the technology on their side, but some of us, now will have it.

[Joey R.]

Thank you all for your answers, but Jeff, this is what I was looking for. I understood that eyes converged but did not know it was necessary for cameras as well. This kind of shoots down my hopes of run-and-gun 3D shooting. If I understand correctly, this means that it is intrinsically impossible to create 3D video that allows the viewer to focus on whatever they want in the image, even if the depth of field is deep, because of the convergence factor required when dealing with nearby subjects.

Is this correct?

HUMAN eyes converge AND focus on the same object. Your eyes are always converging. If they do not converge they become diverged and it causes general uncomfortableness. If they converge too much you become cross-eyed. For 3D you can have it where the convergence and the focus do not have to be the subject. Or maybe you want it to.

In 3D shooting you have two methods of shooting, parallel and beamsplitter. You shoot beamsplitter in order to replicate as close as possible human interpupillary distance. For close up shooting you may want less than that, say .75" or 1.5". There is no camera out there that you can slap side by side that will allow you to get two camera bolted together that will give you the optical centers .75" apart. (Checking Iconix as I write this... :P). Thus the beamsplitter. It allows both lenses to occupy the same space for a 0 interocular or a slight shift for your .75" I.O.

Side-by-side is a must when using huge zooms and great distances. There is obviously more to it but that is the jist of it.