Film-Tech Forum ARCHIVE: Dolby 3D LS light calculations & Infitec glasses

This is topic Dolby 3D LS light calculations & Infitec glasses in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Antti Nayha (Member # 4980) on 01-07-2014, 04:22 AM:

It has been briefly discussed before here, but having limited experience on Dolby 3D, I'm trying to figure it out properly...

Exactly how much more light does a dual-projector Dolby 3D LS setup give you compared to single-projector Dolby 3D?

Looking at the DFC100 installation manual, it says that the optimal dark time is 780 μs (with the larger Cat 948 color wheel) or 1045 μs (with the smaller Cat 949 color wheel). Both numbers are for 6:2 triple flash, so when projecting 24 fps material, there are a total of 24×6 = 144 periods of dark time per second.

So, if I got it right, a Cat 948 system has a dark screen for 11.2% of the time. With a Cat 949 that would be 15.5%.

Now, going from one projector to two, replacing the color wheels with static filters and losing the dark time, you would get:

2×(1+(11.2/(100–11.2))) = 225% of the light
(compared to a single-projector Cat 948 system)

or

2×(1+(15.5/(100–15.5))) = 237% of the light
(compared to a single-projector Cat 949 system)

Am I making sense?

I suppose that the Cat 949 is used in the smaller projectors only, since it's less light efficient?

* * *

Another question: is this stuff compatible with Dolby 3D in a cinema setting? Any experiences?
INFITEC Large Venue
INFITEC Premium Glasses

Due to their small field of view, the regular Dolby 3D glasses are obviously problematic in a giant(ish) screen setting... so I'm looking for alternatives, while trying to avoid silver screen solutions.

Posted by Steve Guttag (Member # 268) on 01-07-2014, 06:17 AM:

Anitti...yes...you should have more than double the amount of light when using a dual projection system (any 3D) since you loose the dark time.

I have no experience with using the infetec brand glasses but I thought that they were the same thing.

Posted by Marcel Birgelen (Member # 6801) on 01-07-2014, 09:53 AM:

Those premium Infitec glasses I got from an exhibition a while back work flawlessly on Dolby 3D cinema systems. I don't know if those are the "premium" ones you pointed at, but they seem to look the same. I really like those bigger glasses and the more "enclosed" design. I've never seen those "large venue" 3D glasses, but they look bulky, uncomfortable and generally not much bigger than the regular glass based Dolby 3D glasses.

Posted by Antti Nayha (Member # 4980) on 01-07-2014, 12:04 PM:

OK, thanks! I agree that the "large venue" Infitec glasses look clumsy and their lenses still seem to be too small... however, they're 33% lighter than the "premium" glasses. Have to ask for some samples.

Posted by Carsten Kurz (Member # 5396) on 01-07-2014, 06:39 PM:

To my knowledge, they are extremely expensive, at least according to their list price.

I would assume they do work with Dolby systems basically, but it could be that they have slightly different spectral characteristics, means, slightly less separation, colour shift, light loss etc. Best is to inquire at Infitec.

Sony offers an Infitec variant under the Dolby 3D brand for their SRX-R320 projector, but they use a different glasses type, probably adjusted to the SRX colour separation filters.

- Carsten

Posted by Antti Nayha (Member # 4980) on 01-16-2014, 04:06 AM:

quote: Carsten Kurz
To my knowledge, they are extremely expensive, at least according to their list price.

Ouch, it seems like you could say that... That's something like 70 to 350(!) euros a pair, depending on type. And the viewing window in the "large venue" model appears to be 31×27mm (PDF brochure), which isn't any larger compared to Cat 834. I wonder why they're even calling them that.

I still didn't hear from Infitec about the Dolby compatibility, but after learning those things I'm not really that interested. I guess the only feasible option for dual-projector giant screen 3D is passive polarization after all.

Posted by Marcel Birgelen (Member # 6801) on 01-16-2014, 04:21 AM:

Hmm, I'm going to handle those glasses with a little more respect now [Wink]

.

Although, I'm quite sure you won't be paying EUR 350 if you'll order let's say, 200 of those [Wink]

.

I don't know if mine are those "Premium glasses" they mention on their site, they look eerily similar and they work flawlessly with the Barco implementation of Dolby 3D, but they're also at least two years old. I don't know a venue around that's using Sony in combination with Dolby 3D.

If you want to go for premium polarizer glasses with large viewing area, maybe you could take a look at Polaroid. They sell a range of those glasses, which work with standard circular polarization systems (RealD, Volfoni, XPand Passive) and they go for anywhere between EUR 10 and EUR 35.

Another thing to consider might be cleaning those things... You might want to check if those things are even remotely dishwasher-proof.

Posted by Antti Nayha (Member # 4980) on 01-16-2014, 06:40 AM:

Yeah, I'm looking at machine-washable polarizer glasses now. As always, any recommendations/experiences are welcome. Thanks for the Polaroid hint, I'll check them out as well.

RealD licensing is not really an option in this case, but presumably one could still buy glasses from them if your 3D system is compatible? I know they're offering dishwasher-proof glasses, not sure about Volfoni or XpanD yet.

It seems to me that pretty much any polarization 3D glasses are large enough for this venue - the screen is not that huge, but large enough that the tiny Dolby glasses just don't cut it.

Posted by Carsten Kurz (Member # 5396) on 01-16-2014, 10:43 AM:

Polaroid glasses are very good. They have a range of glasses with closed or open sides. Optical quality is much better than standard RealD glasses. Plus they are affordable.

The only thing I really do like about polarizing 3D systems is the wide range of choices for glasses because there is no base patent involved...
Bad for Dolby 3D systems, first you pay Dolby, they pay Infitec, and then the glasses production involves multiple layers of evaporation procedures on individual pieces of optical grade bent-glass... They will never be low cost or made larger than absolutely necessary...

Friends of mine designed a 3D system for a special venue and checked all available glasses for compatibility with common cleaning systems. I think they gave up on the Polaroids finally, but for some reason were bound to use an ultrasonic cleaner.

The Polaroid glasses are multiple layer coated, the ultrasonic cleaning probably damaged these multilayer structures.

Polaroid will certainly be happy to make suggestions for proper cleaning procedures.

- Carsten