Film-Tech Forum ARCHIVE: Digital 3D Flicker

This is topic Digital 3D Flicker in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by James R. Hammonds, Jr (Member # 673) on 02-20-2008, 08:05 AM:

I noticed a strange strobe-like flicker during the 3D portions of Hannah Montana the other day, but only in the 3D portions.
The 2D portions look fine.
If you take off the glasses, it looks as if the two images are shaking back and forth.
Does anyone know what causes this?
I've only recently come back into the business after a few years out and know next to nothing about the digital machines.

Posted by Frank Angel (Member # 248) on 02-20-2008, 10:58 AM:

Nothing to know, James....they are designed to be foolproof and perfect so that any idiot can work them. If anything goes wrong, you need to call in that $250-an-hour service tech to fix it. And besides, you must be mistaken....only film has a shaking image, not digital. [Wink]

Posted by Stu Jamieson (Member # 4626) on 02-20-2008, 02:29 PM:

Is it a twin projector 3D setup? If so, it sounds like the convergence between the projectors is off kilter causing image separation.

Posted by Mike Renlund (Member # 4675) on 02-20-2008, 03:53 PM:

That, or if its Real D, maybe the z screen isn't working correctly.

Posted by James R. Hammonds, Jr (Member # 673) on 02-20-2008, 05:34 PM:

Sorry, I forgot to post specifics in my original post.
I wasn't given a detailed rundown of the equipment and I haven't looked at a manual yet, but I'll do the best I can.
The projector is a Christie DLP and it is Real D.
It does have the screen that goes in front of the lens which I assume is the Z Screen Mike mentioned.
I don't know much beyond that.

Posted by Mark J. Marshall (Member # 1409) on 02-20-2008, 05:37 PM:

There's an off chance that you've noticed that the eyes on a single projector system are in fact not in sync.

But then you aren't supposed to be able to see that, so I don't know.

I'm interested to see where this thread goes.

Posted by Steve Guttag (Member # 268) on 02-20-2008, 07:14 PM:

Convergence on the projectors should not cause a flicker but it would cause eye strain.

It sounds more like a sync problem or perhaps the system was put into a 48Hz mode instead of the "triple-flash" that is the most common. At 144Hz, you shouldn't see any flashing.

Steve

Posted by Ken Lackner (Member # 1002) on 02-20-2008, 08:53 PM:

I agree with Steve. Sounds like it is not set for tripple flash. However, it is rather odd that this would just start occuring, and therefore this begs the question, has this problem always happened on all 3D shows in that house?

In any case, it is best to have a qualified service technician take a look, as there is not much you can do about it if that indeed is the problem.

Posted by Ken Lackner (Member # 1002) on 02-21-2008, 07:48 PM:

For poops and grins, I tried a little experiment this morning. I copied the Flat 3D format and saved it as a new format (so I wouldn't eff something up on the real format). Then I went into the 3D settings and changed the frame rate ratio from 6:2 (tripple flash) to 1:1. I ran Hannah in this format. Sho 'nuff, this created exactly the conditions James describes. Very noticeable flicker with glasses on, and a rapidly weaving (for lack of a better term) image with glasses off. This is because the projector is alternating between the two images slowly enough that the brain can perceive the changes, whereas with tripple flash, the alternation occurs so rapidly, your brain perceives it as a single image. (I hope I explained that clearly enough.)

So, if something is set incorrectly in your projector, and it was not like that for previous 3D features, or previous showings of Hannah, I am very curious as to what caused it. My first instinct was to suggest that the wrong format on the projector was selected, because 2D formats would not have tripple flash applied. But if you try to play 3D content in a 2D projector format, the colors will not look right. Since you did not report strange colors (which, IMHO, is more severe of a problem), I am assuming that did not occur. So I wouldn't think the problem was just having the wrong format selected on your projector.

Please keep us updated.

[Confused]

Posted by Tim Reed (Member # 137) on 02-22-2008, 11:50 AM:

Yes, you have to have it set for 6:2. At nearly anything less than that, you can see flicker with the naked eye.

quote: Frank Angel
you need to call in that $250-an-hour service tech to fix it

Humm, I don't get anywhere near that much! Who has these jobs?

Posted by Darryl Spicer (Member # 711) on 02-22-2008, 02:50 PM:

If this is something that has worked fine on other 3-D features but just started giving problems with the Hannah feature then it could be an issue with the server or how the program is set up. There were specifics for setting up the program on the Hannah show because they switched to a different file format for the 3-D. Not sure if you are using the Doremi server but a program patch was available for the server when they Sent out the original keys. If you are an Access/it client then they were supposed to take care of that for you. Make sure that you have the 48 fps setting within the program set up.