Film-Tech Forum ARCHIVE: Dolby Calibration with new Filter Wheel and Glasses.

This is topic Dolby Calibration with new Filter Wheel and Glasses. in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Adrian Hauser (Member # 4723) on 09-03-2011, 06:56 PM:

Hi We have two 3D screening rooms both with Barco / Dolby 3D kits.

The original room has the series one filter wheel and glass based 3D eyeware.
We found the difference bw the eyes when looking through the glasses did not require any "per eye" color correction.
The new screening room has a DP2Kp and new filter kit has also come with newer glassware. straight off the bat the color difference bw the eyes is quite visible. There is also a noticeable difference in the brightness between the eyes with the newer plastic eyeware .
The newer system does appear to do a much better job at reducing ghosting/crosstalk.

Given we are using a single projector setup Im curious to know what most of you are doing to correct for the color differences bw the eyes.
It could be said that with no correction the image looks fantastic although if you alternatively shutter each of your eyes there is a massive color difference that your brain magically fuses back together.

I have tested calibrating both eyes back to DCI white points and can get both eyes balanced in both luminance and color but in comparison the resultant image is a lot dimmer (matching the luminance) and just plain lacklustre.

Thoughts?

Thanks,

ADrian

Posted by Brad Miller (Member # 2) on 09-03-2011, 09:10 PM:

Adrian,

Part of the Dolby 3D setup process is to calibrate the color. Just because it looks "pretty good" out of the box is NOT doing the job properly, and is a disservice to the Dolby 3D system and your patrons.

NO projector will look proper without the color calibration. Grab a club and beat it over your tech's head and tell him to do his job properly. Your complaints are precisely why Dolby has the procedure to balance everything for a specific lens, color wheel, port glass, screen, etc.

Posted by Adrian Hauser (Member # 4723) on 09-03-2011, 10:59 PM:

HI Brad,
I just did a calibration and have it looking very good. The trick is to put the projectors
MCGD file into a Nominal mode and tweak the white points in the per eye LUTS . I now have much better saturation and matched eyes on the new kit. [Smile]

I would still like to point out though that the new plastic glasses are horrible compared to the Glass versions. We have all three versions of Dolby 3D glasses here. The first original glasses were well balanced in terms of luminance between the eyes but compared to the new ones were not as efficient in reducing cross talk/ghosting.

The new plastic versions whilst appearing to have almost NO crosstalk allow very minimal head movement. The right eye in particular has a kind of vignette in it compared to the new glass versions and is a LOT darker. This means that to get a perfect luminance match bw the two you have to reduce the brightness of the left eye to match. You cannot increase the brightness of the right eye because whites will clip to a color because of the huge color shift you have to account for in the Post LUT.

I have cheated a little bit and left the Left eye brighter than the right just to keep brightness and specularity on screen. The White points are now matched.

Adrian

Posted by Brad Miller (Member # 2) on 09-03-2011, 11:53 PM:

No offense, but I seriously think you are not doing this right. Do you even have the proper calibration lenses from Dolby, or are you trying to do this with a pair of glasses?

Posted by Adrian Hauser (Member # 4723) on 09-04-2011, 01:52 AM:

No offense taken Brad.
Although it is rude to make such assumptions.

I have a PR650 Colorimeter and the Dolby 3D Filter Calibration kit lenses AND I am the dude maintaining the color accuracy of the Post Production screening environment.

Like I said I have got the two LR eyes looking very good against one another. The 3D images are now also a very good match to the 2D 14FL images in their DCI P3 Official Color Space with a white point set at x.314 y.351.
Yes they are somewhat dimmer at around 4.5 FL but are surprisingly good looking.

I originally posted this message because straight out of the box the two systems appeared completely different. No joke, the first series1 system did not require any per eye setup apart from setting the overall whitepoint of the projector to P3 when the dolby filter wheel was in. The difference between the two eyes was extremely close. In comparison this new system was WAY off and really needed the calibration to bring it back in. Originally I made the calibrations with the projector set using my P3 MCGD file. With the per eye corrections applied the images looked very lacklustre. Then moving into a nominal setup (Full projector Gamut) I was able to manipulate the color primaries a lot more and thus get a decent result.

My comments still stand regarding the differences between the eye-ware. I think we might send the new plastic lensed eyeware back and order more glass based ones.

Regards,
Adrian

Posted by Pete Naples (Member # 761) on 09-04-2011, 04:37 AM:

Standard practice is to run the projector with Nominal or NominalV2 gamut.

I think this "Given we are using a single projector setup Im curious to know what most of you are doing to correct for the color differences bw the eyes. " is where Brads question lies.

All of us will be doing the per eye colour correction in the server, AFAIK only Dolby and Doremi servers have the facility.

How the eye images 'look' against each other is immaterial, how they measure is.
Although I will admit that with enough experience of different projectors, screens etc, etc, etc one develops a good 'eye' for this. More from the standpoint of 'this is good 3D, or something is wrong'

I'm not surprised you can see difference between series 1 & series 2 projectors with Dolby 3D, the optics in series 2 are different for a kick off, they are a lot more optically efficient and depending on what model your series 1 is, it'll be doing full chip triple flash. I was once told by Barco that there can be anything up to a 10% difference in terms of light throughput and colour matching between 2 seemignly identical light engines.

AFAIK there is no difference in the filter wheels, between the bracket mounted version and the light engine mounted version I mean. They are all made for Dolby by the same manufacturer.

Posted by Steve Guttag (Member # 268) on 09-04-2011, 09:22 AM:

Okay...you've got my interest.

When you say you calibrate the per-eye LUTs (Look Up Tables)...just where are you doing that? In the DLP control software (MCGD1 and MCGD2)? Or are you doing it via the Post Production Communicator software (which most folks do not have access to)?

I have not experimented with using those for 3D (yet) if they can be used for that...I will have a new method for Dolby 3D calibration pretty soon. I would MUCH rather do color calibration IN THE PROJECTOR. That will open up the whole 3D thing to Alternative Content too.

Most folks do the Dolby 3D calibration in the player (and GDC also has that ability in addition to Doremi, and Dolby...I suspect so does CUBE and and everyone else in the DCinema biz).

As for glasses, Dolby has had three that I am aware...The original glass lens version that is still available. There is the first plastic version that was "not for major markets" and the current Plastic "3M" version that I have found a "slight" reduction acceptable viewing range (before having to move one's head to avoid looking through the edge of the filtering).

-Steve

Posted by Pete Naples (Member # 761) on 09-04-2011, 10:05 AM:

Steve, for alternative content 3D there are 'solutions' aka expensive boxes from Doremi and Sensio.

If it could be done in projector, that would save a lot of ££/$$ and a lot of complexity.

This is one of the more interesting threads recently!

Posted by Steve Guttag (Member # 268) on 09-04-2011, 11:04 AM:

Pete,

Yep...I've used the Doremi Dimension 3D as well as the CineTal box for color correction...but oh what a pain in the wallet and effort. This would not eliminate the Dimension 3D box...but it would negate the need for the Cine-Tal...which would be a great start. I also think that one could get a more accurate color balance if done in the projector anyway...rather than alter the color of the files sent to the projector, alter the projector's color. It just makes more sense!

Now, if TI (or the projector companies) can get their software to take a side-by-side or over/under consumer 3D (single stream) and also output that as normal 3D and deal with the HDCP aspect...then the Dimension 3D would be out of a job for DCinema types.

-Steve