Stereoscopic 3D recording on the BMCC possible?

Hi,

Something I think some of us might not be aware of (or could be just be me and I wouldn't be surprised), BMCC does not have genlock.

Does this mean that it is not possible to get *cinema quality* stereoscopic 3D recordings done on two BMCCs?

Thanks for any help,
Jules

I've been told that people have done 3D recording on 5Ds, that also has no genlock, by using LANC to start the cameras together, but then camera drift sets in. I'm not sure why 2 BMCCs should drift being 100% electronic and having no mechanical transport. Would anyone know why drift can occur?

Dropped frames and the like. You don't nes' need Lanc unless it's live, though it is a great help. Get them matched in post and you'll get great results. So yes you will be able to shoot stereoscopic 3D, there will be limitations and experiementing needs to be done. We've done it with 550D's and got great results.

Thanks Michael.

Dropped frames would constitute a re-take surely (for non-live work)? And wouldn't the BMCC pop up a warning that a recording error occurred?

I think the Lanc start allows two camera to be in sync initially. Trying to align in post with 1/24th increments is going to cause phasing issues, I think? but I don't know for sure, 'cause not done a stereoscopic 3D shoot before.

How do you get the focus to be in sync between the two cameras? Do you need special lenses, or lens types to avoid?

Cheers,
Jules

What are you thinking Michael??

You cannot - repeat cannot expect to have usable motion 3D stereoscopic footage from two separate cameras without either a genlock circuit and/or shutter lock between the cameras active. This is etched in stone. Sure you can get 10 or 20 seconds of DLSR footage to work, but the cameras will drift due to the lack of the aforementioned connection, introducing retina rivalry and other artifacts that are uncorrectable in post and make the footage stereoscopically totally unusable.

The only beamsplitter and parallel bar mounted cameras that we professional stereographers recommend are ones that have genlock capabilities at the very least, Red Epic & Scarlet, Sony F3, F65, and EX3, Arri Alexa, etc.

It is misleading and dishonest to state otherwise.

Thanks Michael.

Dropped frames would constitute a re-take surely (for non-live work)? And wouldn't the BMCC pop up a warning that a recording error occurred?

I think the Lanc start allows two camera to be in sync initially. Trying to align in post with 1/24th increments is going to cause phasing issues, I think? but I don't know for sure, 'cause not done a stereoscopic 3D shoot before.

How do you get the focus to be in sync between the two cameras? Do you need special lenses, or lens types to avoid?

Cheers,
Jules

Play and experiment is all i'll ever advise, we're currently working on a dual focus mechanism (as well as a tracking device for 3D work from a kinnect and a couple of laser readers) , remember I'm coming form the very DIY end and as far as I'm concerned anything is possible.

Give you an idea and I state, and I must repeat state categorically do not try this at home. This is what our VFX specialist Sergei gets up to in his spare time.

He rode pillion on the back of the bike whilst they drove around and has decided he'll never do it again. His view was of vehicles getting closer than they actually were and him physically wanting to react. This was 2 years ago, we now have a very nice DIY rig for DSLRS.

So play around. Just maybe not to this life endangering level.

What are you thinking Michael??



It is misleading and dishonest to state otherwise.

Never say never. I also never stated to use it in a "pro" setting, just saying it's possible is all.

Another self made rig test Sergei did with 2 7D's

now these were all tests and yes long footage you do want to do the whole pro using better systems but all of this was done to lead to this which was a competition entry, now how many minutes of footage do you actually need and how you edit it will make a whole world of difference.

filmed on a homemade 3d rig and 2 7D's

"Never say never. I also never stated to use it in a "pro" setting, just saying it's possible is all."

Funny irony in that sentence.

Listen Michael, you can experiment with Lanc and other solutions all day long, but you will never get more than a few minutes of usable stereographic footage before retinal rivalry becomes apparent in the footage like wheels begin spinning in two different directions at once and bird's wings doing the same. Your audience is as important to be aware of as the story being told on screen, and what stereographers understand is that if you give them a headache watching your show, you don't have an audience to show it to.

Believe me, I've tried it with side by side Canon DLSR's and conventional handycams like you picture above. All of the results were unsatisfying and ultimately unworkable.

AFAIK, the BMCC does not have nor is expected to have any genlocking capabilities, at least in this model. So the long and the short answer to utilizing a pair for stereo work is that despite energetic DIY attempts - no it's not possible is all.

Sometimes a few minutes of footage is all you need for a take.

I'm not disagreeing with you. If I needed to shoot 3d for a full on client I would go through your recommended cameras and systems, ( I also wouldn't shoot extreme action on DSLR's) for low budget work though there is great results coming through on the DSLR side with 3D work
http://www.3dfilmfactory.com/index.php? ... d=42:press
anything is possible.

Thanks Michael and Herr,

Such detailed explanations, fantastic! I'm glad to see that the difference of opinion ended amicably.

Cheers,
Jules

When we talk about 'precise sync' between cameras for 3D .. can an experienced/pro/expert stereographer advise what is an acceptable difference .. is it 2 milliseconds, or 1 milliseconds .. or a 1/2 or a 1/4 or 1/100th of a millisecond?

Cheers

Kevin

Hi,
I think I can contribute to this discussion. I've shot 3D with Sony F3 cameras, and Red Ones, and also tried 7D's, 5D's, etc.
Without Genlock, all you can get is somewhat OK 3D. The problem is in the fast motion. All you need to do is try to shoot the slate clapping with two non genlocked cameras. You will notice there will be no way to sync the two images of the slate, because the motion of the clapper is very fast. If the shutters are not synced you can't get a decent 3D image, because the clappers are in different positions for the left eye and the right eye. So, the faster the motion the more problematic it will be if the cameras are not in genlock.
On the other hand I am wondering about this "drift" everyone is referring to. If you genlock two Sony F3 cameras, and disconnect the genlock cable the shutters will remain in sync. The way to confirm this is by using a Transvideo 3D monitor that will only create a stereoscopic image if the two streams are genlocked.
Using the same monitor it should be possible to confirm if two BM cameras can be shutter synced through lanc, and if the cameras will maintain this sync. If they do, I don't see a reason why they couldn't be used for 3D. If not, forget about them. That said, I find it disappointing that BM didn't include genlock, it's a rather simple feature, and it only makes sense to leave it off a camera like this if the company is planing to release a more professional version of this camera (such as Scarlet vs. Epic.) I hope this helped to answer some of the above questions more objectively.

Joerg,

Thanks for replying. There is another way to look at the sync of the two F3, and that's with a dual channel oscilloscope. Where by the two signals would be compared to a reference clock.

I am not familiar with a Transvideo 3D monitor, but I suspect it would have frame synchronisations on the inputs. This is necessary (even with genlocked devices) to correct for differences in cable length.

No two cameras will have identical clock frequencies, there will always be drift even if very small.
Genlock ensures they both have the same clock.

I am trying to gather opinion on the acceptable tolerance.

For example,

A full second or more out of sync is fine for a completely static scene.
A scene which is mostly static is ok with a mis-sync of 1ms.

That 1ms is probably not tight enough for a shot of a car speeding through frame.

My testing has me starting two cameras, with the left eye 0.25ms ahead of the right.
The pair of cameras I am using drift such that I can shoot for 8 minutes before the right eye is 0.25ms ahead of the left.




Cheers

Watt do you think about using http://www.appliedlogiceng.com/index_files/Page1431.htm to sync the cameras?

With a LANC controller the cameras would still go out of sync over time due to the oscillators running at slightly different rates ? I wonder what the rate of de-synchronisation would be ?

Just get this, solves all of the sync problems tight away.
http://www.3dstereo.com/viewmaster/lor-lic-mc.html

I've done plenty of stereoscopic filming (on consumer equipment) to clarify some fundamentals:

Sync:
As long as there is no way to actively synchronize the electronics ALL camera pairs will run at slightly different speeds and thus run out-of-sync after a short while, even if you manage to start them perfectly synced (that is what specialised "LANC-Controllers" do). Running out of sync means that you have up to half an image delay between left and right clip even after "syncronising" the shots in your editing solution. At a maximum recording speed of 30 fps you'll have 1/60 s timing difference in the worst case, or almost 17 milliseconds! This is inacceptable any kind of moving image; even if viewers won't actively notice the delay, they still will "feel" it, because they can't fuse the two different images correctly.

The usual way to get "synced" pairs of cameras in the consumer range (no genlocks) is a kind of "brute force" attack: enthusiasts will group and buy a larger number of the same camera modell, do extensive tests, and then select the best matching camera pairs. This way you can find pairs that will keep in sync (delay below 1 millisecond) for several minutes or even up to half an hour (if you're lucky).

As a rule of thumb i'd accept:
- delay below 1 ms for fast movement (think: sokker)
- delay below 5 ms for slow movement (think: market)
- delay below 10 ms for semi-static scenes (think: skyline)

IO:
The single most important characteristic of a stereoscopic recording is the lateral shift between the recording lenses; this is often called "inter-occular-distance" or short IO, our eyes have an IO 60 to 70 millimeters. This value determines how "deep" the stereoscopic images look: larger IO creates "deeper" images, smaller IO creates "flat" images, but too large IO will produce painfull or even unviewable images.

If you mount two cameras side-by-side usually their dimensions will determine the minimum IO. The BMCC is rather large and not well suited for this kind of setup. A different approach are stereo-rigs using semi-translucent mirrors, this way you can achive virtually any IO you seem fit, from 0 mm up to a dozen cm (for larger IO you don't need a mirror rig). And then there are "stereo-lenses" like the one linked above, yet this is by far the worst solution: these lenses have a fixed IO that is too small for most applications, they reduce the amount of light drastically and they also cut your recording resolution in half (or worse).

The BMCC and BMPC are perfect for use with mirror rigs, a parallel setup would only work for "large" scenes, like landscapes or skylines. The Pocket CC might also be good for parallel setups, probably turning one camera upside down you could get almost "natural IO". I'd not even think about using a stereo-lens in any "real" setup.

very nice to find this thread. Has anyone tried syncing two BMCC BMPC cameras via LANC Shepherd Pro? I've had great success using one to sync two HDV cameras, where degree of sync is measurable before recording (aim for disparity of less than 1/6000 sec) and can be monitored during recording for drift. Worked very well with HDV cameras, fast action items such as falling water were captured in sync. Be great to test on BMCC, but especially BMPC due to how close it can be to natural interocular.

Sadly none of my LANC-remotes, stereoscopic or single, are able to control the Pocket cam, and i doubt it would be different for the 2k5 Cinema cam. So i guess we'd need a new LANC Shepherd or SteFra-Lanc programmed exactly to match the LANC-needs of BMD Cameras...

At the moment i only own one Pocket cam (was hard enough to get this one...), but maybe i'll look into stereoscopic filming again in spring.

Thanks Mac, would love to hear what you discover! I am surprised the LANC on the BMPC is not more compatible with LANC controllers.

someone connected the two camera (pocket camera or black magic cinema camera) to a Teranex 3d, for sync.

in teranex 3d info say: "You can even use two consumer cameras for true 3D!"

anyone tried this

The Teranex doesn't sync the cameras, it only provides framebuffers to combine the frames and output them simultaneously. You won't get "better" stereoscopic recordings this way, the combination is only frame-accurat, while with active sync'ing methods you can (and want to) reach line-accurat or even pixel-accurat timings.

We mount the BMCC on our Beam-Splitter rig, The Robert Rig. As I posted in another thread, we have won major awards without using genlock. It is definitely possible to get cinema quality 3D without it.

I've been thinking about stereoscopic work with my Pocket cam for a while, but decided not to try it, because i'm afraid that lack of synchronization could ruin half the shots.

How do you ensure "better than random" synchronicity? Or just not? Can you provide exemplary clips that contain object and/or camera motion?

We mount the BMCC on our Beam-Splitter rig, The Robert Rig. As I posted in another thread, we have won major awards without using genlock. It is definitely possible to get cinema quality 3D without it.

Any sample videos? Or Screen grabs?

I agree with Michael. Yes, temporal disparity is important but we've found it is often the least problematic disparity (for instance, mismatched zooms are a much bigger problem). If you are careful with your alignment and shoot 3D correctly you can still get a great viewer experience even if there is slight temporal disparity.

Here's a link to a piece that we did that won the Lumiere Award from the International 3D Society. This was judged on a 50ft Lucas Screen entirely by stereographers. The camera moves the entire time and yet the 3D looks great because we shot it carefully and groomed in post. It includes a huge swing shot at the end of the piece.

Chompers 3D
youtube.com/watch?v=gWhzQt9Y6e0

Would it be better to shoot with cameras that had shutter sync? Yes! But lack of genlock does not mean you can't start shooting 3D and get good results. The Chompers piece above was shot with a couple T2is and I would have loved to have shot with Black Magics instead.

We also had another short creative piece get picked up for distribution by 3D Content Hub and even earned a paycheck for that one.

Personally, I think, the most important aspect of good 3D is experience. If you're goal is to shoot 3D well, then get out there are start shooting - even if you can't get your hands on perfect cameras.

note- we're organizing a Black Magic 3D shoot now and will post footage shortly.

So, I guess in all of our debate over the importance of Gen lock - the answer to the question do you want your 3D to look Professional? If yes, then you should sync the sensors. End of story
But I want to ask the question... Is it possible? I mean maybe it just requires some ingenuity, hardware etc... but is it possible? With all of the products for monitoring and processing that BM comes up with... I have to think there is some solution and I might be able to stick two pockets, cinemas or productions together and get a synced image... but that's just optimism. What's the reality?

It's possible to use any cameras for stereo 3d. Lanc or not. You can sync in post and bobs your uncle.

The results will be good enough for YouTube videos for your friends or test projects, but you will never ever be able to charge anyone for this process. It doesn't work. The shutters lose sync and your eyes notice that things don't look right. It's an uncomfortable experience - almost like watching film with the audio track slightly off sync. You need genlock to shoot pro stereo, end of discussion. If you didn't, why on earth would people spend so much money on RED or arri or the F55 for stereo at high resolution for professional use?

None of the BM cameras are capable and I've even had wary comments from tech support of the likely success with the URSA even though it is supposed to have it. Just use another camera. We are looking at some large stereo projects late this year and would love to shoot with either the bmcc or the URSA for the ease of workflow with using ProRes instead of the extra encoding step for using red or arri. We'd be willing to order 6-8 of the URSA cameras but not had any confirmation until release that this will even be possible. If you want a cheap HD solution, try the ex3.