Blackmagic Cinema Camera

[David M. Cole]

http://www.blackmagic-design.com/pro...camera/design/

No Genlock :-(

[Neil Richards]

Boo hiss! I was wondering about that. Why can't they just put genlock on as standard on all non-consumer cameras? AF100 the same.

Transvideo Evolution 3D monitor can genlock two un-synced cameras though, even via HDMI I believe. It's the only one I know that does this. Haven't tried it yet, looking for more info and a trial soon hopefully. Might be a solution for two BMBB's (Black Magic Box Brownies) on a rig...?

[David M. Cole]

It might be able to display 2 independent sources that are not genlocked, but each camera's sensor must integrate in phase for 3D to work. That has to be done at the camera.

There's always the LANC trick, and I'm sure lots of folks will sync thru LANC. It's only initial sync, however, and then the cameras drift.

[Bruce Allen]

Originally Posted by Neil Richards

Boo hiss! I was wondering about that. Why can't they just put genlock on as standard on all non-consumer cameras? AF100 the same.

Oh man... I've mentioned this about two dozen times elsewhere. They always say stupid things like "why not just use the (fixed interocular) 1-camera solutions?" or "a 4/3 sensor is too big for 3D - read this basic primer on 3D TV production" (my favorite - because obviously Cameron, Jackson, Scorsese and Scott are just screwing up... what are they thinking of, shooting with Alexas and Epics?)

Why do the cams that are perfect for 3D in terms of packing good image quality within as small and light a package as possible (Sony FS100, FS700, Panasonic AF100, JVC 4K cams, Blackmagic Cinema Cam) never have genlock?

The funniest thing is that Sony, Panasonic and JVC make 3D projectors / TVs / switchers / blu-ray players etc. You'd think that their ailing TV depts would be on their camera dept's case about making more tools so that we can make good stereo content so that they can sell some more TVs!

Back to the Blackmagic $3000 awesome-cam... they seem really friendly and open. Let's see if we can chat to them about hacking a solution together? At the very least, maybe Applied Logic Engineering can do something cool?

Also, what's the best way to bug them to include this on their next cam (along with 48fps :)? Their choice of EF mount as standard seems to suggest to me that perhaps they have other, larger-sensored, maybe slightly-more-expensive cams in the pipeline that will fit their mount choice better in the future... for sure I think this is just the beginning!

Bruce Allen
www.boacinema.com

[Neil Richards]

Originally Posted by David M. Cole

It might be able to display 2 independent sources that are not genlocked, but each camera's sensor must integrate in phase for 3D to work. That has to be done at the camera.

Transvideo claim otherwise:

CineMonitorHD10 3DView S | Transvideo

Expensive, but I hope to try one out and see how it works.

There's always the LANC trick, and I'm sure lots of folks will sync thru LANC. It's only initial sync, however, and then the cameras drift.

No guarantee this would work on another camera by another manufacturer though.

Genlock isn't rocket science and can't be that much more expensive to include - especially on a "cinema" camera which is likely to be used on multi-camera shoots even if not on 3D.

Still think it's a cool piece of kit though.

[David M. Cole]

Originally Posted by Neil Richards

Transvideo claim otherwise:

Here's what they say, "Thanks to its new embedded synchronizer, the 2 signals don't need to be synchronized. The 3D Single Input allows the processing of an embedded Side by Side signal. The 2 processed SDI outputs deliver the synchronized signals, Side by Side or not."

The display can WORK with non-sunk sources, because it has a frame buffer and can slightly time shift one of the incoming streams to match the other. Additionally, the device serves as a HD-SDI frame sync on the output - just means that the HD-SDI packets on the output are sunk.

This does NOT mean that the cameras are temporally aligned. The baked in disparity that occurs when one camera is not integrating on the same clock as the other - is still there. Using a frame synchronizer is the equivalent to lining up two in depended clips on a frame boundry in an NLE (based on a clap or a flash), and hoping for the best. You can still be off as much as 1/2 frame.

Temporal disparity is the mother of all stereoscopic errors. Fixing (which REALLY isn't fixing -just trying to make somewhat better) requires compute intensive optical flow analysis to try to alter the position of features within each frame. It also often requires hand rotoscoping to fix torn occlusions from the position altering.

[David M. Cole]

Originally Posted by Neil Richards

No guarantee this would work on another camera by another manufacturer though.

Right. But, if it's a proper LANC command set implementation, it should work. The hairy bit is if the cameras will power-up on the wiggle of the LANC data line. IF they will, a stereo LANC controller should be able to start the cameras up with minimal drift and display the drift offset in real-time.

[Neil Richards]

David, that's what I didn't get either - can't see how it could sync at less than a frame resolution so I'm not sure what they are claiming. That monitor has twin HDMI inputs as well and if I read the spec correctly they say it will sync those together in the same way. Specifically, they say this is for stereo rigs using DSLR cameras. Since they then have a sync'ed output for each channel I assumed the idea was that this would then be used for recording.

Be that as it may, I still think there must be a way they could use the Thunderbolt port to tie two Black Magic cameras together. It's fast enough to provide an accurate sync signal, in fact it can already output the full rate data stream. Pretty sure they could identify sync in the slave camera and genlock that way, then perhaps genlock could be a firmware upgrade later on? :)

I'll wait for more news on the way their LANC implementation works. Maybe this is the key, but at the moment just not enough information.

[David M. Cole]

Thunderbolt is our great hope. It's certainly low-latency enough and it's interrupt driven, not polled. I had a friend go camp out at the Blackmagic booth until he could get to someone and ask about a sync solution. As soon as he sobers up :-), I'll get the report from him and share.

[Neil Richards]

Ha ! A friend of mine was there too and I asked him to do the same thing. Let's see what they each come back with :)

[Alister Chapman]

Then once you manage to find a way to sync them you will need to figure out where on earth you get a pair of matching, low distortion lenses with a wide enough field of view for sensible 3D. With a 2.7x crop factor and EF mount only that will be quite a challenge. Your going to want something like a 10mm lens for natural looking 3D.

[Neil Richards]

Alister, crop factor is 2.3, so for example a Zeiss CP2 18mm with an EF mount would be about 41mm, just about ok but smaller would be better.

There's a selection of Canon primes down to 10mm which would give roughly 24mm, not found out if they or anyone in that market have matched versions available.

PL mount would be they way to go really.

[Alister Chapman]

No, the crop factor is greater than 2.3. I've just check the math and while it isn't 2.7 it is 2.45 and this is still significant.


Pl mount would be great, but you can't put a PL on the BMD camera. Maybe a 10mm will make a reasonable wide, but a what aperture and what about all the distortion which would be acceptable as a semi fish eye on a 35mm DSLR, but not as a regular wide on the BMD?

I'd rather stick to a pair of XF105's. They cost less, have wide angle zooms, weigh less, have genlock and Canon backup and support. I think people need to remember that the BMD camera is not much more than a slightly bigger than 2/3" camera head with the ability to record RAW. There are many MVC's out there that you can sync, are smaller, lighter, less skew and with C Mount a much better range of lenses.

The only "cool" thing about the BMD is it's RAW capability, but frankly unless your able to put decent, appropriate glass in front of the sensor that's a bit of a waste. Perhaps BMD Mk2 will have a better sensor size/lens mount combination, or someone will hack one apart and fit it with a C mount of 4/3 mount.

[Neil Richards]

Crop factor of the BMC active sensor area compared to 35mm works out at 2.31, Alister - ok, yes, this is larger than 2.3 ;) - and this is certainly accepted over on the BMCUser forum and elsewhere now. There's plenty of active discussion about suitable lenses. Tokina 11-16 and Canon 10-22 are all in scope.

There's a huge lens choice for EF mount, both from Canon and others, so it's no surprise perhaps that that's where BMD pitched the camera first. However they have already said that both M43 and PL mount versions will follow once the current model is launched in July.

It may be just a bit bigger than 2/3" but it's 12-bit RAW and includes $1k worth of Davinci Resolve in the price. If they get 800 ISO out of it it's low light capability won't be sniffed at either. The dynamic range and grading options are what has everyone hot under the collar. That and the fact that it's a platform that has a lot of potential expansion via firmware/software upgrades.

It's a very interesting development, not perfect yet, but with big potential and a very aggressive price point.

[Tim Dashwood]

Originally Posted by Alister Chapman

No, the crop factor is greater than 2.3. I've just check the math and while it isn't 2.7 it is 2.45 and this is still significant.

I originally thought the BMD camera had the same sensor size as the Panasonic AF100, but it is actually smaller, much closer to Super-16.

I always use Super-35 as my base of comparison for FOV cropping, not full-frame 35, so my calculated 'crop factor' is only 1.5X.

Super-16 = 12.52mm x 7.41mm
BMD 4/3 = 15.8 x 8.8mm
AF100 4/3 = 18.9mm x 10.63mm
S35 = 24mm x 13.5mm

That basically means that if my standard wide lens on Super35 is 18mm, then I would have to use a 12mm on the BMD camera to achieve the same FOV.

Any way you slice it I can't see it being suitable for 3D unless we could somehow access a SDK to control the shutter timing through Thunderbolt. Someone would also have to design a suitable cage that uses the single 1/4"-20 screw on the bottom and the three 1/4"-20 on the top to maintain solid alignment.

I personally think the BMD camera is a great deal for what it does and what it comes with (Resolve & Scopes) but I think I would purchase the FS700 simply for the fun of overcranking at 240fps. At that speed I doubt genlock is very important!