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.

[Markus Stone]

It's counterintuitive to think that you'd have to vary the interaxial (or interocular, if you like to call it that) for each shot when in real life our eyes are fixed, but you do.

Consider if you were doing a 'matrix' shot where the camera travels 'through' the phone lines. Another camera placed 64mm away would be outside of the cable; ie, capturing a completely different image altogether = major eyestrain for the audience.

The human eye has a remarkable ability to deal with things that would otherwise cause eyestrain if caught on camera. I can focus on my finger when it's about 10cm from my nose. I would not shoot the same closeup with a 64mm interaxial/ocular.

My eyes are happily converging on my finger and although the background has way too much parallax due to being overconverged, it's okay because it's way out of focus, and I'm looking at my finger anyway.

The human eye is not like a camera, capturing all parts of the frame equally. We tend to 'see' mostly with the 5 degrees or so of central vision - there was an article on this some time back in New Scientist. If something interesting happens in the peripheral vision, we turn our eyes to look at it. That's why our eyes 'scan' the frame, rather than remaining static, like the camera that recorded it.

So if I’m looking at my finger, I’m pretty much not looking at the background anyway. As soon as I look at the background, the parallax is fine because I have reconverged. Instead, now I have 2 blurry fingers obscuring part of the background.

Stereoscopic cinema presents the world as we would like our audience to see. If I shoot my finger with a 64mm interaxial interocular, the audience may look at the horribly over converged background and accordingly vomit into their popcorn.

This is also the reason why you tend to get a better 3D effect with deep focus rather than shallow depth of field – that, and the fact that your eyes have sharp edge detail to work with throughout the scene to calculate where objects lie in 3D space. BUT it means that we have to create an image that works, no matter where in the frame the viewer decides to look - which is not the same as real life and part of the reason why we shoot with differing distanced between the cameras.

It also has to do with the breakdown of accommodation (focus) and convergence. Even though in real life, your eyes converge AND focus, in the cinema, you only ever focus on the screen (or possibly, your date), while it is solely the convergence that gives you the 3D effect. In real life, focusing on my finger throws the background out of focus, which helps soothe the overconvergence of the background; in the cinema the background stays exactly as the cinematographer shot it.

As an aside, there are various things that, while we accept them in the real world, don't work in 3D. For example, my monitor has a shiny bevel on it that reflects it's environment. Because it’s only 15mm wide, each eye gets a totally different reflection. I don't get a headache from looking at my monitor all day, but if I shot it and projected it, the reflection would probably be annoying.

The reason is that a stereoscopic LR projection is not the same as actual 3D. If I decide to resolve it, I focus and converge on the reflection, move my head, and the reflection moves and shifts. From this I can get a sense of the reflected object. Try this in the theatre and the reflection will NOT shift, in fact the whole world you are looking into will appear to revolve to keep you in the exact same position relative to the objects in the scene.

So I guess in a 3D theatre, the world really DOES revolve around you - at least for 2 hours :smile5:

Cheers
Markus


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.

[Pedro Guimaraes]

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.

umm....if I understand you statement correctly, you are totally incorrect. This is a ton a adjustments on 3D rigs. Alot more than just convergence.

We change IO on a per shot basis! Every situation demands a different setting. In fact in most cases it will be less than 2.5"

While I doesn't matter what camera you use, it does matter what your near and far points in the image are. Most of all it matters what you will be displaying it on. If you are shooting for IMAX and you stick with a 65mm IO on a certain kind of shot your parallax on a 75ft screen will be to big.

So IO settings have to change mostly to conform to viewing screen size, near and far points, focal length being used and a host of other conditions.

Can you shoot 3D with a fixed IO? SURE. It been done alot! Is it ideal not for every situation.? No. Adjustablility is key for 3D. if you take care and shoot things correctly when using a fixed IO you can produce good content, but care must be taken.

just wanted to expand and clear that statement up since the original poster seamed to be new to 3D.

If I misunderstood you post, I apologize in advance.

[Jeff Coatney]

OK, let's clear this up before we all confuse the hell out of everyone reading this thread. Some of you sound like you're confusing the Inter-Occular distance and the Convergence angle. They are not the same and they must be isolated and controlled independently from each other.

Unless you are a Pirate with an eyepatch and a parrot on your shoulder, you have two eyes in your head. Your eyes are 65mm apart, sitting in your skull. This is the (average human) inter-occular distance. Your eyes never move closer together or further apart because they are fixed in the eye-sockets in your head.

When you adjust your two cameras so that the inter-occular distance is greater than 65mm or less than 65mm, you are changing the scale of human vision. If the inter-occular distance is 130mm, you just made everyone in the audience a 12 foot tall giant. If your inter-occular distance is 32mm, you just made everyone in the audience into a 3 foot tall hobbit. When you vary the inter-occular distance, you change the scale of not only the audience, but everything on-screen in your shot. The behind the scenes of the film Coraline illustrates this perfectly since the inter-occular distance on the camera had to match the relative size of the puppets to scale. The inter-occular is typically not adjusted during a shot and 99% of the time is set at 65mm.

The amount of eye-crossing that we humans do is the convergence angle. Here again the distance between our eyes doesn't change, just the angle at which they're pointed changes. This is typically adjusted during a shot to maintain the subject within the Z axis. This angle can change constantly and dynamically in a shot, yet it should be done within a 20 degree range so as not to induce negative responses from the audience.

There are many rigs you can use, but they all perform the same basic principles: replicate human vision. 3D is an attempt to replicate human vision. That's why it works. You can deviate all day long from this paradigm, but it has consequences with how the audience experiences the movie. Just because you can shoot your subjects outside these parameters, doesn't mean it will automatically translate into effective 3D footage. Stay Human! It works 99% of the time.

[Jeff Coatney]

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?

Correct. But you could shoot with a fixed convergence angle and adjust your subject to perform or move within that plane, provided you can control your shooting environment. Or maybe its okay that the subject moves in and out of optimal 3D viewing? Your artistic and content choices would have to determine if this is acceptable.

[Michael Hastings]

OK, let's clear this up before we all confuse the hell out of everyone reading this thread. Some of you sound like you're confusing the Inter-Occular distance and the Convergence angle. They are not the same and they must be isolated and controlled independently from each other...

.....The inter-occular is typically not adjusted during a shot and 99% of the time is set at 65mm.

Stay Human! It works 99% of the time.

Joey, Markus, Pedro - isn't this still incorrect?

i.e. we aren't confusing intraocular:

".....The inter-occular is typically not adjusted during a shot" (that's probably true) "and 99% of the time is set at 65mm" (and that's probably not).

and that intra-ocular is routinely changed for the reasons Markus explained?.

[J.J. Blumenkranz]

I think there is another point to be made about convergence. It can be faked in post by shifting the Horizontal Offset of the images. (I didn't see that mentioned in this thread; If I missed it, apologies.) So, shooting parallel can give you a little flexibility down the road and let you focus on the inter-axial/inter-ocular (same thing). Shooting parallel also has added benefits such as no keystoning artifacts. Of course, it also implies that you have to shoot with some padding to give room for the shifting.

[Mark L. Pederson]

Joey, Markus, Pedro - isn't this still incorrect?

i.e. we aren't confusing intraocular:

".....The inter-occular is typically not adjusted during a shot" (that's probably true) "and 99% of the time is set at 65mm" (and that's probably not).

and that intra-ocular is routinely changed for the reasons Markus explained?.

Sometimes you will rack IO, convergence & focus - all within a shot. But I'd agree that you will typically rack convergence more than IO while rolling.

"99% of the time is set at 65mm" is not a correct statement. You COULD do that - if you want to shoot simple, safe 3D - but I'd be shocked if any folks doing 3D features are doing that - we are certainly not.

[Michael Hastings]

Sometimes you will rack IO, convergence & focus - all within a shot. But I'd agree that you will typically rack convergence more than IO while rolling.

"99% of the time is set at 65mm" is not a correct statement. You COULD do that - if you want to shoot simple, safe 3D - but I'd be shocked if any folks doing 3D features are doing that - we are certainly not.

Mark, thanks for clarifying.


I think there is another point to be made about convergence. It can be faked in post by shifting the Horizontal Offset of the images. (I didn't see that mentioned in this thread; If I missed it, apologies.) So, shooting parallel can give you a little flexibility down the road and let you focus on the inter-axial/inter-ocular (same thing). Shooting parallel also has added benefits such as no keystoning artifacts. Of course, it also implies that you have to shoot with some padding to give room for the shifting.

I touched on your point in another thread. But it is an important one.

I think in essence it boils down to this:

3D adds a whole 'nother level of complexity to shooting movies.

As I stated in post #3, you can do some very interesting things - and get a lot of practical experience with a simple side by side rig (It can be useful just to see how things work as subjects/objects move in and out of the frame/side to side, etc.). And it can be pretty useful for simple stuff: like my underwater nature shoots where you are basically just assembling clips of interesting stuff and throwing out whatever doesn't work; a short tradeshow commercial piece where you are just going for the gimmick effect; 3D porn; etc.

But it would also be mistaken to think that you would try to shoot a full length feature type movie these days without the capabilities you get from using a full-featured rig like ET makes.

[Jeff Coatney]

Sometimes you will rack IO, convergence & focus - all within a shot. But I'd agree that you will typically rack convergence more than IO while rolling.

"99% of the time is set at 65mm" is not a correct statement. You COULD do that - if you want to shoot simple, safe 3D - but I'd be shocked if any folks doing 3D features are doing that - we are certainly not.

So if simple and safe 3D can be achieved using a 65mm IO, how is it not a correct statement? You're implying that you shoot complex, unsafe 3D. What distance do you set your IO typically?

[Jeff Coatney]

As I stated in post #3, you can do some very interesting things - and get a lot of practical experience with a simple side by side rig (It can be useful just to see how things work as subjects/objects move in and out of the frame/side to side, etc.). And it can be pretty useful for simple stuff: like my underwater nature shoots where you are basically just assembling clips of interesting stuff and throwing out whatever doesn't work; a short tradeshow commercial piece where you are just going for the gimmick effect; 3D porn; etc.

But it would also be mistaken to think that you would try to shoot a full length feature type movie these days without the capabilities you get from using a full-featured rig like ET makes.

Michael, this is a complex topic. Its difficult to discuss even when you have images to illustrate it. I have no doubt that you are aware of the parameters of 3D. If you're building rigs, then you know what you can get away with for the look you're after. There are many 3D rigs that have been utilized in recent history, yet there's a dearth of real understanding of the underlying complexities. Don't take my comments personally. I just think its important to make a clear distinction of these concepts for people reading this thread that haven't built and experimented with their own rigs yet.

[Michael Hastings]

There are many 3D rigs that have been utilized in recent history, yet there's a dearth of real understanding of the underlying complexities. Don't take my comments personally. I just think its important to make a clear distinction of these concepts for people reading this thread that haven't built and experimented with their own rigs yet.

Thanks, Jeff. I don't take it personally, because although sometimes these forums can suck when they get bogged down in endless "A is God, B and C suck 'cause they bring out new cameras every 3 months" posts - this thread is an example of the beauty of the internet: We've already got great input from yourself; Joey; Markus; Pedro; J.J.; Mark L.; and we're only 20 posts in - that's a hell of a (virtual) room.

I've been in the video industry for 25 years and consider myself an expert in a fair part of it - but other than very simple stuff 3D is new to me. I can pick up a fair amount of it from research but it is extremely helpful to have these professionals weigh in and clarify things.

[Petri Teittinen]

This is an excellent thread, please do go on, gentlemen. I'm thinking about making my own rig once the 8x Scarlet is out, so this is gold for me.

(sorry, off-topic) I think someone brushed briefly on this earlier... my pet peeve, so to speak, with modern 3D films has to do with the use of shallow DOF. While it's perfectly fine (understating it radically) in traditional moviemaking, it bugs me immensely when used in 3D features. The main reason for this is the fact that quite often I would like to focus on a different plane than the one decided by the director.

I was really frustrated by this when viewing Avatar; there was so much interesting stuff on screen, but Cameron wouldn't let me see it all on my leisure. I guess this is why I think CGI features are better suited for 3D. Not only do CGI features generally appear to cultivate a much deeper DOF than live action films, they have the capability of practically infinite DOF, with everything in the frame in perfect focus. I wonder if that could actually work with current 3D technologies, and whether it would allow my eyes to focus on whatever plane/depth they wanted in the frame.

[Markus Stone]

Hi Petri,

One of the practical issues is that you lose a stop of light simply by putting the cameras on a mirror rig, which puts you behind the eight ball a bit when it comes to adding even more light to the scene to get a deep depth of field. It's possible, of course, but not necessarily practical.

-Markus

[Pedro Guimaraes]

Stop = more light= more $$$$$

Add to that 1 stop loss on the beam splitter, iso 200-320 of the RED, low budget.....shallow focus is unavoidable.

Make a strong argument for using smaller sensor cameras for 3D.

Do you know how much light they used in muppets 3D to shoot at F11? enough to have a few of the puppeteers pass out under the stage from heat exhaustion!!

Coraline had lots of issues with the mini "set & actors" shrinking and expanding due to heat from lighting! A big issue when your shooting stop motion 3D with on DSLR motion control rig. For example a bed might of been 2" inches long at the beginning of the shot then hours later it had expanded due to heat to 2.2" !! Eventually they figured out the problem and addressed it. just goes to show some of the issues people have had on trying to shoot with a deep focus and lots of light required for it....

Talk about making actors uncomfortable and trying to keep them from sweating! So There real world issues in achieving a F8 - F11 indoors on location. Hell even a 5.6 can be hard to get on the RED one/beamsplitter combo.

[Pedro Guimaraes]

OK, let's clear this up before we all confuse the hell out of everyone reading this thread. Some of you sound like you're confusing the Inter-Occular distance and the Convergence angle. They are not the same and they must be isolated and controlled independently from each other.

I'm not confused.

IO is one thing and convergence is another.

In Simple terms think of IO as a 3D volume knob. Convergence on the other had mainly determines where the screen plane is.

Actually they don't have to be controlled independently. For example the ET rig automatically adjust the convergence when you adjust IO to keep the screen plane where you set it. It's a great feature! So in the ET case they are linked.





The inter-occular is typically not adjusted during a shot and 99% of the time is set at 65mm.

While we don't "pull" IO that often we it's done more that just 1% of the time.

I can also tell you from numerous 3D productions I have been on that in fact we rarely stay at 65mm IO. So your figure is definitely incorrect in that regard.

I'm doing a 3D shoot tonight using the ET rig/Reds and a Cunima beamsplitter on a technocrane. I can almost guarantee most of the time we will be below 65mm....except for some of the wider shots. Good chance of us changing the IO during the technocrane shot.


This is typically adjusted during a shot to maintain the subject within the Z axis. This angle can change constantly and dynamically in a shot, yet it should be done within a 20 degree range so as not to induce negative responses from the audience.

I wouldn't even say "typically". In reality alot of the productions I have been on have not "pulled convergence". This is a phenomenon that Cameron is a big fan of. He uses it like focus pulling. Controlling in a way what the audience is seeing. A moving "window" is not always something you want.

Completely opposed to Cameron's convergence pulling method, there are lots of good reasons and lots of good people that like to shoot 3D parallel and converge in post. You eliminate the keystone distortion that you create with toe'in the cameras. Shooting at 4k you have plenty of pixels to shift the images and adjust the convergence in post. In fact if you keyframe your convergence pull that is way more accurate than even highly skilled hands of a convergence/foucs puller. Plus once you coverge during shooting, your kinda baking that in. Shooting parallel keeps that creative choice for the 3D edit review room.

Naturally if you shooting a live 3D event you need to converge at the camera. Or if you have zero budget for 3D corrections in post (which is scary thought). Otherwise there are very strong arguments to shooting parallel.



There are many rigs you can use, but they all perform the same basic principles: replicate human vision. 3D is an attempt to replicate human vision. That's why it works. You can deviate all day long from this paradigm, but it has consequences with how the audience experiences the movie. Just because you can shoot your subjects outside these parameters, doesn't mean it will automatically translate into effective 3D footage. Stay Human! It works 99% of the time.

If you only had to change the IO from 65mm 1% of the time than every 3D rig would have a fixed IO!

anyways,

Rigs are sometimes very different in what they can perform. Especially when you on location in heat, humidity, cold, rain and on a tight schedule. This is why the best ones are more expensive. They more accurate in less time! If your spending $100k for a shoot and you don't "make" your day because you spent so much time fiddling with your rig. That is a big problem! Angry producers!

I always strive to NEVER have the production waiting on "camera" to be ready. having a good rig is key to make this a reality. I love yelling out "camera's ready".


I would say, 3D is an attempt to FOOL your eyes and your brain that you are seeing depth. Not that it's an attempt to replicate human vision. Cameras do not work the same as eyeballs. Also we don't have a "frame around what we see. We need to deal with a phisical screen plane and a screensize issue. We have to balance a variety of factors focal lengths, IO, convergence, near&far points, object in the distance, not having any window violations etc.....all in an attempt to fool your BRAIN thru your eyes that you are seeing depth. It's not a replication of human vision or else the dolls in Coraline would lool like 2" dolls. They don't, because like you mentioned they scaled the IO to trick our brains into thinking those dolls being photographed were much bigger than they were.

To be able to execute this magic trick properly we need to balance many factors....including the IO.

Look it's really simple. Take a slide bar and your DSLR. Go shoot your best friend from across the room with a 65mm IO. Then with the same lens and IO put the camera 2' in front of his face. The results will not be good. Reduce the IO to say 1.25" and you will have better results. He will not look like half the size he was. IO does of course affect scale but there are other factors involved.

My best advice to learning about 3D is ......go out and experiment! Grab your iphone if thats all you have and start shooting some stuff. If you have a DSLR try shooting things in your backyard from different distances and with different focal lengths....you will witness and learn the most intriguing things!

Best way to learn is to just do it.

[Michael Althaus]

Lot's of good information in this thread. Does anybody know if there is a simple software to simulate shooting 3D? I imagine something like a simple virtual set where you can mess around with all the parameters (IO, Convergence, f, etc.) and observe the results in realtime. Of course you could do it with any kind of 3D modeling program, but I'm looking for a very simple solution just for learning purposes....

[Jeff Coatney]

I'm not confused.

IO is one thing and convergence is another.

In Simple terms think of IO as a 3D volume knob. Convergence on the other had mainly determines where the screen plane is.

Actually they don't have to be controlled independently. For example the ET rig automatically adjust the convergence when you adjust IO to keep the screen plane where you set it. It's a great feature! So in the ET case they are linked.

While we don't "pull" IO that often we it's done more that just 1% of the time.

I can also tell you from numerous 3D productions I have been on that in fact we rarely stay at 65mm IO. So your figure is definitely incorrect in that regard.

I'm doing a 3D shoot tonight using the ET rig/Reds and a Cunima beamsplitter on a technocrane. I can almost guarantee most of the time we will be below 65mm....except for some of the wider shots. Good chance of us changing the IO during the technocrane shot.



I wouldn't even say "typically". In reality alot of the productions I have been on have not "pulled convergence". This is a phenomenon that Cameron is a big fan of. He uses it like focus pulling. Controlling in a way what the audience is seeing. A moving "window" is not always something you want.

Completely opposed to Cameron's convergence pulling method, there are lots of good reasons and lots of good people that like to shoot 3D parallel and converge in post. You eliminate the keystone distortion that you create with toe'in the cameras. Shooting at 4k you have plenty of pixels to shift the images and adjust the convergence in post. In fact if you keyframe your convergence pull that is way more accurate than even highly skilled hands of a convergence/foucs puller. Plus once you coverge during shooting, your kinda baking that in. Shooting parallel keeps that creative choice for the 3D edit review room.

Naturally if you shooting a live 3D event you need to converge at the camera. Or if you have zero budget for 3D corrections in post (which is scary thought). Otherwise there are very strong arguments to shooting parallel.



If you only had to change the IO from 65mm 1% of the time than every 3D rig would have a fixed IO!

anyways,

Rigs are sometimes very different in what they can perform. Especially when you on location in heat, humidity, cold, rain and on a tight schedule. This is why the best ones are more expensive. They more accurate in less time! If your spending $100k for a shoot and you don't "make" your day because you spent so much time fiddling with your rig. That is a big problem! Angry producers!

I always strive to NEVER have the production waiting on "camera" to be ready. having a good rig is key to make this a reality. I love yelling out "camera's ready".


I would say, 3D is an attempt to FOOL your eyes and your brain that you are seeing depth. Not that it's an attempt to replicate human vision. Cameras do not work the same as eyeballs. Also we don't have a "frame around what we see. We need to deal with a phisical screen plane and a screensize issue. We have to balance a variety of factors focal lengths, IO, convergence, near&far points, object in the distance, not having any window violations etc.....all in an attempt to fool your BRAIN thru your eyes that you are seeing depth. It's not a replication of human vision or else the dolls in Coraline would lool like 2" dolls. They don't, because like you mentioned they scaled the IO to trick our brains into thinking those dolls being photographed were much bigger than they were.

To be able to execute this magic trick properly we need to balance many factors....including the IO.

Look it's really simple. Take a slide bar and your DSLR. Go shoot your best friend from across the room with a 65mm IO. Then with the same lens and IO put the camera 2' in front of his face. The results will not be good. Reduce the IO to say 1.25" and you will have better results. He will not look like half the size he was. IO does of course affect scale but there are other factors involved.

My best advice to learning about 3D is ......go out and experiment! Grab your iphone if thats all you have and start shooting some stuff. If you have a DSLR try shooting things in your backyard from different distances and with different focal lengths....you will witness and learn the most intriguing things!

Best way to learn is to just do it.

LOL! Pedro, I have no doubt that different techniques prevail on different films. Everyone who's tried their hand at 3D has used their own experience to inform how they do it. You have yours and I have mine. There is one thing I have found to be true: while there's no school of thought that has yet prevailed above any other, everybody's an expert :).

[Joey R.]

PEDRO made perfect examples of why you don't want to shoot at a set "human" inter-pupilary all the time. You also can't ONLY shoot parallel if your subject is 5' in front of you. And you can't shoot beamsplitter with subjects 500 yards away on a 2500mm lens. Ok you could but the rig would be completely unwieldy and the glass required would cost more than the rig.

And BTW, with the ET rig's control you CAN actually separate IO from C if you so choose but the whole point of the software is to prevent problems and to constantly calculate the proper CONV tangent whenever the IO is moved. And vice versa.

[Christer Engstroem]

Mr Cameron put it this way:
"Interocular distance varies in direct proportion to subject distance from the lens. The closer the subject, the smaller the interocular. The farther the larger. A shot of the Grand Canyon from half a mile away may have a 5' interocular. A shot of a bug from a few inches away may have a 1/4" interocular. Interocular tolerance is subjective, but there is a constant value of background split which cannot be exceeded."

More to read:
http://www.3dathome.org/webpage.aspx?webpage=1952

.c

[Markus Stone]

One thing I would add is that it also depends upon how far away the background is.

If your BG parallax is at an acceptable level when looking past your bug to the distant horizon, and then someone places a flat 4 inches behind your bug, suddenly your scene has no depth. You have to open up your interocular if you want to maintain the same sense of 3D.

It is even possible to have a long lens shot with a *larger* IO than a short lens shot, (but obviously in different situations). It depends not only upon the camera - subject distance, but also on the camera - background distance. These together determine how close something can come to camera (out of screen) and still be comfortable.

[Pedro Guimaraes]

like I mentioned there are numerous factors that can affect your IO decision. One of which is your back ground......is it homogenous? do you have many geometrical lines in your background? i.e: prison bars, certain buildings.........what the contrast like in the scene? lot so black and white things next to each other? i.e: like a checkered flag?

Really there is ALOT that can factor in to a IO decsion. That is why 3D pre-viz zoftware can only get you so close. You have to evaluate everything in the frame being shot and made a decision.

Jeff your right, everyone does do 3D differently. There are some rules but most can be considered suggestions. There are even some rules that should be broken on occasion for the right effect of course!

What matters is entertained happy viewers. Because they pay my bills = )

[Pedro Guimaraes]

Lot's of good information in this thread. Does anybody know if there is a simple software to simulate shooting 3D? I imagine something like a simple virtual set where you can mess around with all the parameters (IO, Convergence, f, etc.) and observe the results in realtime. Of course you could do it with any kind of 3D modeling program, but I'm looking for a very simple solution just for learning purposes....

Yes, The closest I know of is Frameforge pre-viz software.

It allows you to set up a scene (cgi), set your camera rig and settings put on your glasses and view the results of a dynamic camera move thru your virtual set either with anaglyph or with your 3D TV set (active glasses or passive polarization).

You can learn alot from playing with it. But it is no replacement for shooting stereo in real life for learning purposes. Like I said you can just use any old digital camera to start taking stereo pairs and learning. I'm sure you already have a digital camera of some sort and PS on your computer. There you have it a free stereo lab for your education.

But frame forge is cool and has it's value for many purposes.

http://www.frameforge3d.com/previz/

http://www.frameforge3d.com/Products/Stereo-3D/

[Stephen Pizzo]

As if there hasn't been enough discussion of variable IO, I would like to add:

Consider that we refer to a lens as normal when it yields a perspective similar to human vision. For example, in the 35mm motion format we call 50mm normal and in the 35mm stills format we consider 75mm normal. These two lens/format combinations give us roughly a 27⁰ FOV which when coupled with a 65mm IO can work very well in creating pleasing stereo images. As the FOV gets wider the IO needs to get smaller to maintain a natural look without miniaturization. Conversely as the FOV gets narrower the IO will generally need to increase to maintain a more natural look while avoiding the cardboard cutout quality.

Now I know this is just one consideration in figuring out the correct IO but Pedro, Markus and others have covered a lot of ground and passed on a lot of really excellent hard earned knowledge. We at ET are engineers and technicians, not filmmakers. As a result we have been around an awful lot of very talented stereographers and stereo supervisors. Through this we have seen many styles of calculating proper IO+C. Some conservative and some radical. In all of this I would say that there is no single IO distance that seems to be used more than any other. There is certainly nothing special about a 65mm IO distance unless you also have the magic FOV of 27⁰. Even then; subject distance, negative parallax in the deep background or even screen size will force you to change the IO to something other than 65mm.

I would also like to add that Pedro's suggestion of experimentation is right on the money and well worth trying. If you're here on this forum then it is safe to assume you like to make images. You will have a blast making stereo images and learn so much, so quickly.


Stephen Pizzo
Technica3D.com

[Bruce Allen]

This is such a great thread!

I agree with all of you in different ways - Pedro, personally I think you're dead on with everything you say about interocular. Disagree with you RE shooting everything parallel and doing convergence in post though! I'm on the Cameron side of things there ;)

Even when doing CG renders for 3D, we still do a little toe-in. Feels a little more natural to us. I do render extra wide though (2048x1080 or 2200x1080 instead of 1920x1080) , so that we can adjust the overall depth when sitting in the 3D online session though. Yes, I've been known to keyframe this ;)

RE: shallow depth of field... Avatar didn't bug me as much as I thought it would. I found that my eye was naturally led to the sharp point of the image - which was where the 3D convergence etc worked well. I think the problem with having EVERYTHING in focus is that then you eye can focus on something in the extreme foreground - but this doesn't feel natural because our eye muscles "know" we're actually focused on the movie screen?

The biggest problem to me is always when the 3D breaks the edge of the frame - you've just gotta stage things properly so that there are no bright foreground objects doing that, I guess! Although I'd be tempted to do a test with "fake" pillarbox black bars on the left and right 10% of the screen (which objects are in rare cases allowed to break). Don't think that'd work too well though.

BTW, what shutter angle are you guys using nowadays? For CG I did many tests with different shutter angles and usually ended up in the range of 60-120 degrees shutter. I know we need to move to 48fps, but oh man is that going to suck for render times...

Bruce Allen
www.boacinema.com

[Michael Hastings]

This is such a great thread!

I agree with all of you in different ways - Pedro, personally I think you're dead on with everything you say about interocular. Disagree with you RE shooting everything parallel and doing convergence in post though! I'm on the Cameron side of things there ;)
Bruce Allen
www.boacinema.com

I think everyone is on Cameron's side when you talk high level production. In high budget projects where everything is well planned and you know exactly what you are going for then manipulating all of those things with a proper rig is important and worthwhile - probably essential.

The point of shooting parallel and converge in post is that for learning purposes or simple/low budget projects it is probably more straightforward and may be less likely to create bigger problems.

[Tim Whitcomb]

As if there hasn't been enough discussion of variable IO, I would like to add:

Consider that we refer to a lens as normal when it yields a perspective similar to human vision. For example, in the 35mm motion format we call 50mm normal and in the 35mm stills format we consider 75mm normal. These two lens/format combinations give us roughly a 27⁰ FOV which when coupled with a 65mm IO can work very well in creating pleasing stereo images. As the FOV gets wider the IO needs to get smaller to maintain a natural look without miniaturization. Conversely as the FOV gets narrower the IO will generally need to increase to maintain a more natural look while avoiding the cardboard cutout quality.

Now I know this is just one consideration in figuring out the correct IO but Pedro, Markus and others have covered a lot of ground and passed on a lot of really excellent hard earned knowledge. We at ET are engineers and technicians, not filmmakers. As a result we have been around an awful lot of very talented stereographers and stereo supervisors. Through this we have seen many styles of calculating proper IO+C. Some conservative and some radical. In all of this I would say that there is no single IO distance that seems to be used more than any other. There is certainly nothing special about a 65mm IO distance unless you also have the magic FOV of 27⁰. Even then; subject distance, negative parallax in the deep background or even screen size will force you to change the IO to something other than 65mm.

I would also like to add that Pedro's suggestion of experimentation is right on the money and well worth trying. If you're here on this forum then it is safe to assume you like to make images. You will have a blast making stereo images and learn so much, so quickly.


Stephen Pizzo
Technica3D.com

any chance I can get a message or call back from ET regarding availability of Rigs? No offense meant, but ive left messages and sent emails for a month and have had NO REPLY...

hoping posting here will get better results. thanks! :)

[Joey R.]

Tim, my apologies but this is the first I am hearing about you trying to get a hold of one of us. I will PM you my cell phone number so I can be reached directly.

Also as a side note, we have doubled our square footage and now have a dedicated facility for Engineering, Admin and demos. The move would have made getting a hold or us difficult for the past two weeks.

Joey

[Tim Whitcomb]

moving, totally makes sense. Ill contact you shorttly.

everyone else, thanks for such an amazingly helpful thread...

[KETCH ROSSi]

The guys over at ET, surely do know what they are doing, and love the space available in their new facility, was great seen Stephen, Hector, and getting to know the rest of the crew, Chris is also very knowledgeable 3D Tech and Stereographer, and Joey and I spent a considerable amount of time on the ET 3D rig.

I have always considered ET to build excellent gear of precise and high quality, and after my recent visit I found the decision to go with their 3D rig for my project, a simple one, as the rigs are extremely well built, and have great electronic and remote controls, even so we will be shooting some scenes on the current large rig with two R1' we very much look forward to their Medium size rigs for the Epic and Scarlet.

Joey, was a pleasure discussing my project with you, and look forward in our tests as soon as you guys are set up for it, you guys rock, and any one interested here, and serious about any 3D work should not hesitate in contacting ET, even so they are now many 3D rigs out there and some cheaper then others, here you do get what you pay for, and 3D is an extremely complex animal, even in its simplicity is still complex, and if you don't have the right rig, you really are up to putting your self in more trouble then is worth.

[Charles Angus]

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.

From everything I know, this is not correct. Large interocular distances can be used for distant subjects, to increase the 3d effect, or to cause the subject to look smaller than it is. Vice versa for small interocular distances.

It is also not necessarily desirable to converge the cameras. Convergence can be adjusted more precisely in post (it's easy, too - you just slide one image left or right relative to the other). Shooting with the cameras parallel (ie no convergence) also has the benefits of not keystoning with wide lenses and making post compositing easier (largely because of keystoning, but it also makes it easier to adjust convergence as you are not fighting what was done on set). I know this from experience compositing on 3d stereoscopic projects.

I would personally only ever shoot parallel 3d...

[KETCH ROSSi]

Well the 65mm or 2.5" is the average human distance of the i/o and for this a Stereo set up to match human vision needs to be set up at such i/o distance, and this is called ORTHOSTEREOSCOPY, but this is not the standard, even so you can shoot tone of stuff with it, there is no way to match a 3D rig with both i/o and convergence control, and more so with A image splitter set up, as they just simply give infinite adjustment capability.

Both i/o distances and convergence are used to create different perceived image distance, size, volume, and obviously depth, were we control not only the size and or 3D effect but we control were the subject is placed inside or outside the screen.

But also the most important things to understand, or at list one of the most important, when shooting S3D, is that the i/o distance controls not only the effect of the given captured image, and create Giantism or Dwarfism effects, but it also dictates the minimum distance in which the camera can be placed, and or must be placed, while convergence focusing dictates were your you are placing your subject in great control.

For the above reasons, a 3D rig must offer extensive and absolutely precise control of the camera movements, usually one fixed and the second one fit to make all control settings.



There is so much to Good S3D that I just have never more in love with the art then since I started studying 3D MovieMaking, and promised my self that I will shoot all or almost all my project in S3D, I just simply love it.