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Canon XL H Series HDV Camcorders
Canon XL H1S (with SDI), Canon XL H1A (without SDI). Also XL H1.


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Old July 4th, 2008, 05:04 PM   #1
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Something weird happened...

We were testing out a 3D rig today with two identical XLH1's. Both were set to HDV F1. The weird thing was that, while both cams were zoomed out, one of the cameras had twice the focal lenght. Even the Z numbers in the VF were the same.
Being new to this camera, and no manual in the cases, I checked all the switches on the lens, and browsed through the menu to find a solution. This went on for about five minutes, untill I switched from F1 to i. The camera booted up again and, apparently, the lens did a reset as well, as now both the lenses were fully zoomed out...

Another thing:

On one of the cameras all the indicator lights (power etc.) were off. Is this a setting as well or is it just broken?

One more thing:

The TC of both cameras need to be synced. We have one day of editing and don't have the time to fuss with drifting TC. How serious is this problem with the XLH1?

Thanks
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Old July 4th, 2008, 05:40 PM   #2
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Dear Pascal,

1. I have no answer for your lens issue.

2. In the menu, in the System Menu, the LED on/off will control the external lights.

Off is a stealth recording mode, so it will look like the camera is off.

3. I find the timecode on the XL H1 to be stable.

You can easily jam the timecode from one camera to another.

Set the timecode you desire on one camera, then use a BNC cable from the timecode out to the timecode in on the other camera.

Be sure that the timecode options in the menu are setup properly. Use 24 hour run timecode setting.

This only takes less than 10 seconds for the receiving camera to align itself (jam) to the other camera. Then you can disconnect the cable.

Re-jam at your convenience. I would do it at least every four hours. You can run a test to see if they remain in sync.

If you can leave the timecode cable connected, both cameras will stay in timecode sync.

For 3-D, you may want to use GenLock.
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Old July 5th, 2008, 05:48 AM   #3
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Hi Dan,

Thanks for your reply!

I guess I would've found out about the stealth mode once I got my hands on a manual, but I appreciate it!

The director checked the test footage in FCP, and as it turned out, we had a 2,5 frame difference between the two cameras. He couldn't tell if it was consistend throughout the footage. We'll be looking into an external TC generator.

The footage will be used on the new Philips 3D screens: http://www.business-sites.philips.co...out/Index.html

Not sure how important Genlock will be, but it wouldn't hurt as you turn on Genlock and TC sync at the same time anyway.
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Old July 5th, 2008, 06:13 AM   #4
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Dear Pascal,

You do not need an external TimeCode generator (at least not to maintain perfect timecode sync between the two cameras. The Timecode Out of one camera can be connected to the Timecode In of the second camera.

If you have a good timecode generator, such as the Ambient timecode generator in a Sound Devices 744t, 788t, etc., then you can use that as your master timecode source. You could also use an Ambient timecode slate. There are, of course, other brands, and other timecode generators.

My main point is that each of your XL H1's can also generate timecode, so you do not technically need an external timecode generator.

Also, since you are shooting 3D, I assume that both cameras would be relatively close together. As such, a simple BNC cable (and the Canon XL H1 manual to read up on their timecode facilities) are all that you need.



I have never needed to use GenLock on any of my shoots, but I have never shot 3D.

If you have a BlackBurst generator (not a timecode generator), then you can send the signal to both cameras, and the start of each frame of video with start at the same time. This is what is used if you want to instantly switch, in real time, between two cameras. This makes for smooth cuts between the two cameras.

In 3D, I do not know if exact alignment of the start of each frame is important or not.
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Old July 5th, 2008, 07:12 AM   #5
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I would think genlock would be very important for 3D where the perception of depth comes from slight offsets in the images from the two cameras. These offsets should be from perspective differences - not because the subject is moving and one camera takes its picture half a frame later than the other. Fortunately genlocking two XL-H1s is easy. Just connect the composite (or component Y) output of one to the Genlock input of the other, set the menus appropriately and check that the lock indicator on the slave side panel indicates lock. T/C lock is, of course, also desireable and is easily implemented by connecting the master camera's T/C out to the slave's T/C in. Presumably the two cameras are close to one another so that short cables can be used (be sure to get 70 ohm cable) and there is no need to fiddle with the pre/post trigger menu setting.

Genlock and timecode can, of course, come from a master blackburst generator or a pair of Lockits as well as from one of the cameras but the latter seems silly as they are so close to one another.
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Old July 8th, 2008, 04:26 PM   #6
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Hi guys,

Thanks for the replies!

We'll be running two Ambient clockit units to the cameras for TC and Genlock. It's better to be safe than sorry!

I really have no experience nor understanding of the technology involved to create these 3D images. The production company and the 3D specialist do know what they're talking about, so I'll just trust their judgement when they say that TC sync is crucial. Haven't heard anything about Genlock, but we'll plug it in anyway.

We'll be having another test with a modified rig and clockit units tomorrow. I'll let you know how it turns out.

Thanks again!
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Old July 8th, 2008, 06:20 PM   #7
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Do you mean a pair of Lockits? The Clockit is usually used to sync Lockits. Lockits synced to the same master oscillator in the Clockit are sync'ed to each other. Also Clockits don't produce video sync (genlock signal) - just timecode and word clock.
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Old July 8th, 2008, 11:52 PM   #8
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Pascal,

With your lens issue is it possible that you knocked the "focus" button on the camera? if you have the evf display turned off you may not notice the "focus" word show up on screen. I think changing the frame rate would reset the viewfinder, and thus "solve" the zoom problem. I've had it happen to me a couple of times, especially when monitoring on an external monitor.
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Old July 9th, 2008, 05:02 PM   #9
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Uhmm it's indeed called a lockit! The producer called it clockit. And it'll be slaved from the soundguys mixer, at least the initial sync, then they will run on internal batteries.

After fiddling with the settings of these units the cameras did sync tc and genlocked properly, yay!

http://www.ambientaudio.com/products/timecode.html The top one

@Nick:

Would you see the "focus zoom" on the external monitor as well? The monitor was pretty much swamped with camera info (tv screen on) zoom indicator, iris, shutter, 25F, HDV, timecode, battery life, safety marker, centercross and 4:3 marker for aligning the cameras. So I could've missed the word focus! (even though it's right there in the middle of the VF (I dug up a manual!))

Thanks again guys!
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Old July 13th, 2008, 05:36 PM   #10
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A quick follow up:

Even with the two Ambient lockits there was still a 1 frame difference between the two cameras...

Or the editor is doing something wrong, or there's something wrong with these cameras.

The lockit units got there sync from the soundguys mixer. The guy at the rental co where we tested this setup checked the settings of the cameras, so everything should be running perfectly. We'd got TC and Genlock but, well, something's off...

Anyway, I've given up on getting these cameras to sync: they will have to adjust it in post...
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Old July 14th, 2008, 07:25 AM   #11
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I'm not clear on all the details in this particular case. The usual procedure with Lockits is to sync their internal oscilators to a Clockit by means of a 1.92 MHz signal supplied by the Clockit. Comparison of the device's 1.92 MHz with the Clockit 1.92 allows the Lockit oscillator to be "tuned" to match the master. This is necessary to get the Lockit(s) and Clockit precisely on the same time base. The Lockit can be jammed to external timecode without this tuning step but best accuracy will not be acheived unless the tuning step is performed. The basic timimg rate of LTC timecode is 2.4 kHz. The 1.92 MHz signal is 800 times more precise.

Lockit/Clockit tecnology is great if the cameras must be separated. I would think that in this case they would be within a few cm of each other so that cables are easily run between them. Exact sync between cameras can only be acheived with cable connection (or an equivalent rf based sync distribution system). As sound is apparently an issue the Lockits could be used to sync one camera and the recorder and the second camera could take it's sync from the first camera. At least the cameras will be in precise step even if the sound is off a wee bit.

It is, of course, entirely possible that the offset is coming from the capture process.

Last edited by A. J. deLange; July 14th, 2008 at 10:24 AM. Reason: Finished dangling sentence.
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Old July 14th, 2008, 08:29 AM   #12
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Hi A.J.

The rental co suggested the option of using one Lockit and have camera 2 receive the TC from camera 1. But what I fail to understand is: what difference does it make where the TC originates? The internal TC of camera 1 should be just as good as the one coming from the Lockit, right?

The TC is generated by a Sound Devices digital recorder with Ambient Clockit(?) I assume the soundguy knows what he's doing, because the recorder and Lockit are his. The second Lockit is from the rental house. Both units were given fresh batteries.

Too bad you didn't finish your last sentence. I'm curious what exactly could be entirely possible ;)
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Old July 14th, 2008, 10:39 AM   #13
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Pascal,

From time to time it is necessary to remind ourselves that time code is not a synchronizing signal but rather a time tagging signal. While it is true that there is a precise relationship between frame rate and timecode which can be exploited in some systems it is Genlock that actually keeps cameras together. SD 7xxT recorders contain Lockit circuitry so they can be synchronized to a master Clockit and develop a word clock which is very close to the Clockit's word clock for a reasonable length of time. At the same time other Lockits (which have been sync'ed to the same master Clockit) can produce Genlock signals which are very close to being in time with the master. When the 2 cameras are tied together be it by a pair of Lockits or a cable it is the Genlock signal which controls when the individual frames are exposed. The time code is merely recorded on tape.

It is sometimes helpful to think in terms of setting a group of watches to show the same time. Setting them all to midnight when the Greenwich Observatory says it is midnight is equivalent to jamming with timecode. The clocks will thenceforth tick off the seconds but none of them will do so at the rate of exactly one second per second (as defined by GMT) so that some number of hours later they won't read exactly the same. To make that happen will require the equivalent of a genlock signal which would adjust the running rates of each watch according to the differences between GMT and the watches' readings taken at frequent intervals.

If a SD 7xxT recorder is declared master then a Clockit can be tuned to it (running rates set to be the same) and the running rate transferred to 2 Lockits. These can be used to tie the frame rates of the cameras together and the word clock of the recorder will be in sync with the video. We haven't said anything about Time Code at this point and time code is, strictly speaking, not necessary if a slate is used to "tag" video and audio so they can be aligned. If time code is available (as it is in this case) then that should replace the slate as the alignment means but one can still find a whole frame or frame offset in some situations depending on how the software in the NLE reads and processes timecode. A better result will be acheived if one of the Lockits genlocks the master camera and the second camera is genlocked to the master by cable. This eliminates the small, but real, drift between multiple Lockits and the two cameras will run at exactly the same rate. The NLE may still introduce a frame or so annomaly


This is all very confusing and the manuals are terrible. It is important, therefore, to experiment with the setup you are going to use to be sure the equipment performs the way it is supposed to. Always have a slate event of some sort in the video and sound as a check.

Good luck!

Last edited by A. J. deLange; July 15th, 2008 at 10:24 AM. Reason: Complete post.
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Old July 15th, 2008, 03:17 PM   #14
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Pascal,

It would indeed be mirrored in the external monitor, it really depends if you have tv mode on or not, and what you're using (the on screen display obviously isn't sent through the hd-sdi port, but is sent through the composite) however the HD-SDI port would receive the magnification which is what has happened to me before, or at least I would go in and set focus and here the director, or producer or whoever was monitoring, say "don't zoom in" or, "I like that shot, can we roll like that?" or whatever.

I've used a time code sync box exactly once, and now rely on an evertz masterclock that supplies both time code and genlock. (it's also pretty darn expensive, but that's why you rent right?)
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Old July 25th, 2008, 05:25 PM   #15
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Hi guys,

To follow up on this 3D adventure:

We did a final sync test at the location (lithuania of all places) and played it back in the camera using the remote and to our surprise the sync was solid. I had a brief talk with the director about this and he told me that the sync was never really that far off. The producer kinda relayed the message wrongly...

So all our efforts in prep pretty much went into getting these cameras to sync, but equally important was to get these cameras aligned properly on all three axis.

A little back story:

At first we tested the two cameras on a square plate with slots machined into it. We didn't have enough freedom of movement on the pan axis and we couldn't quite secure the cams in place, so we tossed that idea aside. The next testing day was at the rental company. Our 3D expert went there the day before and discussed the possibilities. Pretty much every idea was tossed aside as well, and he left... When I arrived, the guy at the rental company grabbed something out of a bin that might work; some wing shaped piece of metal with holes at the ends and holes in the center. He stuck some rubber strips around the holes at the ends and mounted the two XL H1's. The new configuration was better than the one we first tested and the cams were less likely to come loose. I talked with the 3D expert on the phone and he gave us the go ahead.

However: this rig was never intended to have micro adjustment possiblilities to allign the cameras... so with some pieces of cardboard and paper we were able to get them alligned as good as we could, and we were save as long as we didn't zoom in beyond 50% or so.

I have never felt so awkward on a shoot as on this 3D shoot. I was an operator in the most basic meaning of the word; make sure exposure is set correctly, in focus and run the tape. The director and 3D expert pretty much set the frame.

Anyway, I appreciate all the effort you guys put in to provide me with answers for this, to me, new camera!

Thanks

Pascal


This thread has gone in a different direction than what I first intended, perhaps a mod could change the titel to something more appropriate??
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