ft. lamberts, screen size/gain, DLP (1 Viewer)

[Mark.F]

I am in the process of setting up my home theatre and have had various input on the ft. lamberts that I should be ending up with. Here is the setup:
My seating distance is 16ft. from screen. The projector I am waiting for is an Optoma H76 (they say it will be here before 2005 ). The projector claims 1000 ANSI lumens and a 2000:1 contrast. Now here is the catch, the screen size I am going to purchase is 65 x 116. So I am trying to figure out what gain I should go with. My debate is between a 1.3 gain or 1.5 gain Da-Lite screen. The ft. lamberts is 24 on the 1.3 and 28 on the 1.5 gain.

My reason for the confusion is that I called Stewart, Da-Lite, InFocus and Optoma and got very different answers from each. On Stewarts website they reference 12 ft. lamberts. When I called them they told me 18 ft. lamberts for a DLP projector (stating that the DLP's are not very accurate with their ANSI ratings) and this is why the difference from the 12 stated on their site. Then InFocus said 25-32 ft. lamberts and so on....

Opinions please....

 

[Rick Guynn]

I would assume that the actual light output from the projector would be around 700 lumens after proper setup, based on past relationships between 'rated' output and what is reported in reviews after calibration for other PJs.

If I recall correctly, the SMPTE standard is 16 ft-lam. So shoot for something around that. Of course what you actually need will vary depending on light control and personal taste. I have seen plenty of posts from people perfectly happy with numbers as low as 7-8 ft-lam. I have seen others that run a PLV-70 with a HiPower and getting close to 50 ft-lam and happy...

RG

 

[Kevin Korom]

1000 lumens is most likely very optimistic; it could be anywhere from a half to a third of that after calibration. For instance, my "1000" lumen BenQ 8700 is in the mid 400s when calibrated.

This is very common for the numbers to be nowhere near realistic. They are usually rated at a very high color temp, with the whites crushed. Fixing this drastically drops the output. This doesn't just happen with PJs; ISF'ed TVs do the same thing.

As for how many foot-lamberts, the trend these days is for more and more, but it very much depends on your personal preferences, and light control in your viewing area, etc. While a very bright picture catches your eye, it can be fatiguing, and source material flaws are much more obvious. Stewart's recommendation of 12 ftL is about the best you'd see at a typical film screening, and many theaters may well be in the 8-10 ftL range. I believe that the recent showing of ROTK I saw (while looking quite excellent) was no more than 10 ftL or so.

I think most would probably prefer a bit more than that, but I personally find somewhere around the 18-20 ftL mark is the point where quick bright/dark transitions can get too painful for me. And as FtL go up, so do black levels.

I would recommend waiting until you have your PJ, and trying some temporary setup. That way you can get a feel for how bright the PJ is, and whether you want a lot, or a little more brightness.