Film-Tech Forum ARCHIVE: Lumens needed for proper 3D

This is topic Lumens needed for proper 3D in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Tom Wienholt (Member # 1510) on 02-23-2012, 01:16 PM:

I will be converting two screens to digital projection with RealD XL 3d systems. Both screens are common height 12'x28' and have a throw of 55'. What lumen requirements are necessary to properly show 3D movies with the RealD XL system?

Posted by Dominic Espinosa (Member # 2122) on 02-23-2012, 05:03 PM:

My math may be wrong but I believe roughly 691 (at the screen) lumens on a screen that size with lens and lightfilters in front of the meter

My bad. I misread your post. That's a good question...any one know what the light loss is through the filter and glasses?
You will also need to know what the loss is through the port glass.

Posted by Monte L Fullmer (Member # 2797) on 02-23-2012, 05:52 PM:

With those two measurements, I've seen 3K bulbs used for Real D w/XL units at smaller locations using new silver screens.

-Monte

Posted by Tom Wienholt (Member # 1510) on 02-23-2012, 09:09 PM:

Would it be possible to use a 2k bulb with an RealD xl system with this screen size and throw? Or if using a 3k bulb would the z-screen be sufficient? (this would avoid having to modify my ports)

Posted by Sam D. Chavez (Member # 1841) on 02-23-2012, 09:58 PM:

What is the projector?

Posted by Tom Wienholt (Member # 1510) on 02-23-2012, 10:04 PM:

Basically, we are trying to decide between an NEC1200C and NEC2000C. Since the 1200C is cheaper, we would prefer that system but only if it would be sufficient for 3D using RealD.

Posted by Monte L Fullmer (Member # 2797) on 02-23-2012, 11:44 PM:

Have you poked into looking at Christies, or Barcos?

These units do better with light effiency than NEC.

..and into Dolby 3D instead of Real D which you can use your existing screen-no silver screen. Dolby, you own the system outright, but with Real D, a lease is required plus percentage from tix sales heads to Real D.

Posted by Sam D. Chavez (Member # 1841) on 02-24-2012, 12:02 AM:

The dealer or agency of record needs to do the calculations to let you know your options. There are programs to estimate the needed light in Foot Lamberts and it will guide you to a good choice in projectors.

For sure, you do not want to cut it too close or customers will think they are watching a film in a cinema with Sony equipment.

It's not like film where you can buy a bigger lamphouse. Once you buy it, that's it.

Posted by Antti Nayha (Member # 4980) on 02-24-2012, 05:36 AM:

Another vote for a white-screen solution! As you probably know, both RealD and MasterImage require a silver screen which pretty much destroys the image quality for both 2D and 3D in my opinion.

Dolby, Panavision or XpanD on a white screen will all give you much better image quality – although compared to RealD XL, these 3D systems do need more lumens from the projector to achieve the required brightness levels. As pointed out by Monte, the NEC isn’t a particularly light-efficient projector. A B-series Barco or a Christie CP2220 would give you much more lumens per watt, allowing you to use smaller lamps and save money in the long run.

Even if you choose to go with a white screen, an existing matte screen might not be a the most cost-effective solution. A new white screen with moderate gain will still give you great image, and will allow you to use smaller lamps (again, returning the cost of the new screen in the long run). Depending on the shape of your auditorium, a 1.4 gain white screen might be a great choice. Or if your screen is curved, you could even go for 1.8.

Personally, I would probably choose XpanD, a 1.4 gain white screen, a Barco DP2K-19B and a 3000 W lamp. I know that active shutter glasses are not very popular in the States… But with Dolby or Panavision, you need about 50 % more light compared to XpanD.

Pardon my little rant there. I do realize that you may have already made the business decision to go with RealD, in which case that wasn’t much help…

Also, expect Steve G. to drop in any minute now and enlighten you about the benefits of anamorphic lenses with your common-height screen. [Wink]

Posted by Tom Wienholt (Member # 1510) on 02-25-2012, 11:36 AM:

I haven't looked into Christies or Barcos. But, since they are known to be more efficient, I will investigate further.

Posted by Tom Wienholt (Member # 1510) on 03-07-2012, 04:01 PM:

After talking to several people from RealD and NEC projector dealers, I was told that an NEC1200C with a RealD XL system would yeild over 6fL on a 2.2 gain 12' x 29' common height silver screen. Can anyone on here confirm this?