Film-Tech Forum ARCHIVE: MasterImage and Ghostbusting

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Posted by Carsten Kurz (Member # 5396) on 09-20-2010, 05:21 PM:

I'll just bring this issue over from a german forum:

Since a few months now, dedicated 'prefabricated' ghostbusted DCPs have become obsolete, being replaced by realtime ghostbusting performed in the server ('RealD EQ'). The servers received software updates which enabled this functionality.

Now, there is another system that needs ghostbusting - MasterImage. Although their website claims they don't need ghostbusting, they use the same low separation circular polarizing technology as RealD and I'm sure it is prone to the same amount of ghosting. Unless there is a fundamental separation efficiency difference between the ZScreen and the rotating MasterImage Wheel.

Now, 'GhostBusting' is patented by RealD.
In the past, it seems to have been common practice to supply ghostbusted copies to anyone who required them - thus MasterImage screens received GB DCPs, although they were mastered under a RealD patent.

Today, realtime ghostbusting is done in realtime on the server, but only if you have a RealD license key installed. That means for MasterImage installations - no GB DCPs, no realtime ghostbusting.

Any comments?

- Carsten

Posted by John Wilson (Member # 269) on 09-20-2010, 05:36 PM:

I was told Master Image does not require Ghostbusting.

Posted by Carsten Kurz (Member # 5396) on 09-20-2010, 05:55 PM:

That's what they say. Probably because they don't have a patent for it. I assume this is the strategy they are going to communicate. We'll see wether MasterImage installations will suffer from ghosting artifacts more often now that no GB DCPs are available anymore.

The separation efficiency of MasterImage is said to be the same as RealD.

I'm wondering wether Technicolor uses ghostbusting technology in the mastering process for TC3D. Maybe RealDs patent doesn't apply for film?

- Carsten

Posted by Steve Guttag (Member # 268) on 09-20-2010, 08:33 PM:

Having worked with both MasterImage and Real-D...MasterImage does NOT need ghostbusting...it is a vastly superior 3D to Real-D...which even with ghostbusting...ghosts. They patented a fix to the problem they created with the Z-screen.

Furthermore, MasterImage is more efficient than Real-D (standard Z-screen).

Steve

Posted by Dave Macaulay (Member # 813) on 09-24-2010, 12:41 AM:

My interpretation of ghostbusting is that it blanks the image during the time a Z-Screen is electrically switching polarization. The MasterImage wheel has no such switching time, alternating polarity filters are on the rotor in front of the lens and its spin rate is synchronized to the L/R image stream. There may be a period when both filters are in the light path (I haven't examined a filter wheel) and some ghosting will occur but this doesn't seem to be an issue when viewing MasterImage 3D. Dolby 3D would have the same issue, their filter wheels are not polarizing but they alternate "opposite" filters synchronized to the L/R image stream.

Posted by Steve Guttag (Member # 268) on 09-24-2010, 05:28 AM:

Nope, it isn't a form of "blanking" we have that with "dark time" which is the period that no image is being projected to allow the wheel/shutter to change to the other eye. Not having enough dark time WILL cause ghosting but that is not the extra Ghostbusting that Real-D needs.

Posted by Marco Giustini (Member # 4544) on 09-25-2010, 02:59 PM:

As far as I know ghostbusting works approximately adding a "negative" version of one eye to the other one. The ghost effect would cause an eye to leak in the other one, adding itself to the perceived image. Adding a "negative" image (it's not just negative of course) to the eye, would cause the leaking image from the other eye to "fill" it, restoring the original one.

Easy example: you have a grey picture on L eye. Black background with white bars on the R eye. The ghost would make you see Left eye like a grey frame, with brighter gray bars.
Just take Right eye, reverse it, and subtract (partially) to Left eye before showing it. Now if you watch Left eye covering your right one, you'll see a grey frame with slightly DARKER bars. The ghost will raise the brightness where the gray is darker, restoring it to the original level!

Does it make any sense?

This is why ghostbusting doesn't work when the background is black: you can't go below it!

Posted by Steve Guttag (Member # 268) on 09-25-2010, 03:46 PM:

...Unless you project, "blacker than black" [Wink]

Posted by Marco Giustini (Member # 4544) on 09-25-2010, 03:53 PM:

it could be an idea, to show movies with VIDEO levels (16-235) to reduce ghosting. They could call it "LCD effect"! [Smile]