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-   -   Stereoscopic with two 7D's (https://www.dvinfo.net/forum/3d-stereoscopic-production-delivery/474855-stereoscopic-two-7ds.html)

Tony Reidsma March 15th, 2010 08:20 PM

Stereoscopic with two 7D's
 
Ok, I stated in another thread that I was going to shoot 3D with the new Pana camera, to which I was disappointed that I can't get for rent till later in the year.... So, I went and bought two 7D's and I LOVE them!

I'm looking at getting a side-by-side rig from Jasper Engineering (Jasper Engineering: Twin Camera Bar).

Here's a few shots we did during our testing period to determine convergence ranges.
3D - a set on Flickr

If anyone has any hints and such let me know... I've never done this before.

Thanks

Tony

Bruce Schultz March 17th, 2010 05:52 PM

I've been using 2 7D's as 3D 'training wheels' for a few months now.

The Inter Axial distance on a rail/bar is right at about 6", which is a little over 2X your Inter Occular distance between both eyes. So using the 30:1 formula, I try not to feature shooting anything closer than around 15' from the cameras. I use two sets of matching lenses, 28mm f2.8 and 50mm f1.4. I find that shooting outside I need to use a .6 ND for proper exposure, as I like to shoot at 200 ISO and f22 isn't closed enough on a bright sunny day.

Also, it REALLY HELPS to use some kind of a slate mark at the head of each camera record roll for post sync. Don't expect to be able to use the footage with sync sound though as the the cameras are not capable of being genlocked and they will drift somewhat. All in all, I'm happy with what I have learned from using them.

Lastly, I recommend trying out Tim Dashwood's 3D Stereo Toolbox software for FCP if possible. This little plugin taught me more than I can express about how to properly shoot 3D footage through trial and error.

Tony Reidsma March 17th, 2010 08:36 PM

Bruce,

Thanks a ton for your post, most helpful!

I just ordered my bar and will shoot some footage this weekend, hopefully... it's supposed to snow....

I have used FCut in the past but ordered ADOBE's master collection to give it a test drive, being that I'm very comfortable with ADOBE's other apps I assume the learning curve will be brief.

Tony

Bicky Singh March 19th, 2010 01:28 AM

How would you recommend using the Canon 7D's or 5D's for professional 3D capture?

Even though the two camera's will not be perfectly in sync with each other, are you capable of getting them relatively close in post?

I'm planning on purchasing a pair of Canon T2i/550D to see how well they work for professional work. I hear the 7D and the T2i's video capture are almost identical in quality.

Tony Reidsma March 19th, 2010 09:18 AM

You sync in post, use a clapper.

The 7D is fine, more than fine, for professional use with 3D.

Get a fast lens (2.8 fstop or faster) and do plenty of testing to find your convergence point.

Tony

Kaspar Kallas March 19th, 2010 09:51 AM

Hi

Excuse me but none of the not-syncable camera are most definitely NOT "fine" for professional work, because any sort of movement produces false depth. Rolling shutter twice as bad - that is why we use one camera upside down even on synced cameras that have rolling shutter, to have the rolling the same direction. All these artifacts are very visible and produce unnecessary eye-strain, pleases defer using such setups for paid work - for testing and getting the feet wet, for the price why not....

-Kaspar

Bruce Schultz March 19th, 2010 08:14 PM

Kaspar is right, Canon 7D's for 3D cannot be construed as a professional solution. All of the things he mentions are correct as well as a certain amount of 'retinal rivalry' which occurs when the cameras get more than a few frames out of sync. I've found that the best method of shooting with them is to either shoot very short bursts or long nature shots - think mountains in the distance with some trees pretty far away not moving too much.

I use the 7D's as training devices, I recommend looking at them this way for 3D work and in that regard they are a very cost effective way to learn 3D do's and don'ts.

For sync sound and pro use I use a beamsplitter mirror rig with cameras that can be genlocked and timecode synched. That is the only way at this point to insure perfectly matching footage.

Adam Stanislav March 19th, 2010 10:32 PM

Quote:

Originally Posted by Kaspar Kallas (Post 1502018)
we use one camera upside down even on synced cameras that have rolling shutter, to have the rolling the same direction.

Sorry, but would not using one camera upside down and one straight up make the rolling go in the opposite directions?

Kaspar Kallas March 20th, 2010 10:22 AM

Hi

if you use 50/50 mirror both x and y get flipped so we flip the x back manually and deal with the y in post (or in camera for SI)


-Kaspar

Adam Stanislav March 20th, 2010 11:33 AM

Oh, with a mirror. OK, that makes sense then.

Tony Reidsma March 21st, 2010 12:00 AM

Quote:

Originally Posted by Kaspar Kallas (Post 1502018)
Hi

Excuse me but none of the not-syncable camera are most definitely NOT "fine" for professional work, because any sort of movement produces false depth. Rolling shutter twice as bad - that is why we use one camera upside down even on synced cameras that have rolling shutter, to have the rolling the same direction. All these artifacts are very visible and produce unnecessary eye-strain, pleases defer using such setups for paid work - for testing and getting the feet wet, for the price why not....

-Kaspar

I guess I didn't think of this, but I guess I'll see how mine comes out.... Good thing the client already paid.. :-)

Bicky Singh March 23rd, 2010 05:12 PM

So, if i understand this correctly, if I only use the 7D's for quick shots that last for maybe a few minutes. The frames won't be so out of sync that it produces severe retinal rivalry?

Is there a workaround that can deal with the rolling shutter problem. I've read on other forums that many cameras suffer from this, maybe not as severely as the 7D's but it's fixable. Maybe Kaspar can shine some more light on this topic.

Adam Stanislav March 23rd, 2010 05:52 PM

Retinal rivalry is bad whether it lasts hours or seconds.

Bicky Singh March 23rd, 2010 07:39 PM

I totally agree, I wouldn't want to produce any sort of retinal rivalry whatsoever. But from what I'm getting, it sounds like even though the two cameras can't be genlocked and if your only shooting for 1 or 2 minutes per shot, the frames won't go so out of sync that will produce retinal rivalry. Or did i get that completely wrong?

Best,
V

Nick Hiltgen March 23rd, 2010 09:40 PM

If they're not in sync your eyes will be suffering from retinal rivalry. If you want to see this firsthand start your cameras and then take a flash and point it at both lenses. When you play back your footage from both cameras you'll see how the shutter is in different places on either camera during the flash.

There is always a small chance that your cameras would be pretty close to being in sync on start up, but there's the same possibility that your cameras would be completely out of sync. Anyhow take that random starting time and realize that if they were traveling at the same rate without drifting then you may be able to adjust the cameras slightly in post with some plug in I've never heard of. But they wouldn't be traveling at the same rate because the cameras drift micro/milli seconds which compounds your retinal rivalry.

How do you fix this? You feed the cameras a signal to lock to and it solves your retinal rivalry, unfortunately there is nothing that will do this yet for the 7d cameras. Maybe in the future it will happen but not now. I think when you see it you'll realize the extent of the problem. Or perhaps you won't consciously realize it but you will have a splitting headache after a couple of minutes.

On the other hand I believe that enough people do attempt this and it catches on, we can train our brains to not need a genlocked source. But I have absolutely nothing to base that on except my own theories.


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