Paul Bourke wrote:

I was referring to the Optoma Ep1080 which is 3600 ansi lumens.

But what about the contrast? The Dell is precised 2700:1 versus 5000:1 for the Optoma.
Is it significant? That's what refrain myself to buy it.

Hard to tell, these rating are imprecise.

As Paul says, what manufacturers list as contrast is sometimes not close to reality.
Projectors that are not as bright can be listed to have more contrast just because they don't put
out as much light.   I've seen a projector listing only 2000 to 1 contrast that looks much
better than one that lists as 10,000 to one just because of color saturation and sharpness.

I'm in charge of sending the ALMA planetarium show worldwide.
http://www.cosmicorigins.org/
But as I use only Windows and Linux, I have a lot of trouble in making a 1920x1920 Quicktime .MOV for those wanting it.
I tried the instructions that they gave to me (photojpeg, etc...) usable with Quicktime Player Pro but it crashed on my machine (windows XP, Core2duo 3GHz with 4GB of Ram) with an "unexpected error occured".
I tried different sizes of domemasters and formats. Sometimes, going further but not until the end of the process so far.

Strange, the size should not be a problem as I've done 4K with no problem. But then I use Macs so can't really comment on the MSWindows version of QT PRO. I'd happily build the QT movies for you but perhaps it is too late for that now.

I already have the ALMA show as a Quicktime.  But then, I also use a Mac.(g)
Mine is 1536x1536 for my system.  But I have done 2000x2000 for others.

E-mail me directly if you have other questions.  I suspect your Quicktime
settings have problems.

-- Clear DARK Skies
Jack Dunn - Mueller Planetarium