Not RGB!

As expected, using technology identical to DLP or DMD, our projectors do not project 3 colours (Red, Green, Blue). Instead they output four channels (in this order: LBRG). L is sort of a Luminance boost to push light-contrast a bit further in these projectors. To test this we made this simple experiment: rapidly move a white "thing" in front of the light beam coming from the projector, and capture this in a photograph with an exposure time long enough to get the various instances frozen in time by the projector's vertical refresh frequency.
Doing this when a bright white color is projected reveals all the base colours the projector is outputting.These two images show what happens when a white peace of paper is flown through the light beam at high speed, when the light being projected is of a dim colour or a bright colour.

If you are curious to try this yourself, the exposure time is mostly only relevant to make sure you catch the object moving in the field of view. These pictures were 1s in duration. To get the colors bright enough you should play with photographic aperture and film/sensor sensitivity. This is obviously true for exposures really longer than the projector's refresh rate, and if you assume a completely black background.

For curiosity, I don't know why the order in which the colors comes out is this particular one. I would place Green and White at the most opposite palces in time. This I would do arguing that our eyes are most sensitive to Green (and "white") than other colors.. So LRGB would be fine for me, as could imagine that the "blinking frequency" (frequency of intensity changes detected by our eyes) would be harder to spot (would appear 2x higher: low-high-low-high vs high-high-low-low).

Demos Day

Today we had three teams of visiting students in our lab. They totaled about 60 and came from a few Portuguese professional and secondary schools. The visits were themed after the Wall -- our big screen -- and our very recent multi-touch table.
The first visit ran quite well without any problem; projector #12 turned off at the end (lamp has ~1700 h, so it could be understandable).

The second demo started off less well, as suddenly the "Batalha" demo didn't want to start up; improvisation had to shift the focus out of the Wall for a while so that a few processes on the machines could be killed to restore a good working condition. This was a particularly crowded demo and one with less well behaved individuals, some of the equipment must have felt vulnerable to abuse, and the tracking computer mysteriously showed the famed Windows blue screen because of a memory error. After reboot, tracking was back online, and the demo continued.
The third demo also had many people inside the room, but things ran slightly better. However, projector #7 -- one with a 390h lamp -- decided to turn itself off unexpectedly!


In my personal view, these visits showed that for some audiences, there should be a maximum number of persons inside the room. This number should take into account the demos to show: Observing the Wall as like standing during a cinema session may allow some 15 individuals to lay around with comfort; A demonstration involving tracking will require more unobstructed area inside the room for a presenter to move around, reducing the room's capacity slightly; and the multi-touch tabletop, typically designed to interaction of very few people cannot have more than another few watching it. As you can see in the picture, the "success" of showing the table was "attracting" people too close to it.

#8's lamp exchanged

The projector in position #8, had his lamp exchanged! The procedure involved accidentally braking a handle of the used 1772-hour light bulb, but resulted in a successful operation!
To take the cover out, one needs to unscrew a special breed of Philips-compatible screws, similar to one-way only, that are meant to make it more difficult to loosen than to tighten them. I wanted to write here a complaint about this, however I think I understand and agree with the safety of putting such a screw there.. I will probably have to change a few more light bulbs in order to write about it..
The reason behind changing the 1772h lamp was the projector consistently shutting down after only some 30 seconds of use. The bulb's life time should be quite higher, around 2500h..