garageCube

Hi,
I'm new to video mapping, so maybe this is a stupid question but :
I've been playing around with madmapper which work like a charm, but I can
seem to mask the "black background"... my projector still emits a dimed light..

For practice I setup my projector in front of a white cube, and I was able to map
different images on different sides, but on the wall, behind the white cube there is
still a light (that matches my projector resolution...)

I don't think its normal since I saw a bunch of 3d mapping that was pitch black around
the objects..

So what am I missing ?
(I did the mask in madmapper, but it only mask the images...

thanks !

I don't know any projector that has absolute blacks… This varies depending the technology (LCD, DLP, LED, LASER/LED) but every projectors do that.
The projector works like this: light source -> "pixels panel" -> lens.
The light source is always turned on and the blacks are produced by the "pixel panel" producing the most opaque pixels possible which is never really opaque.

You can hide it with ambient light but your projector will need enough lumens to compete with the ambient light.

eventually you can
- adjust your gamma
- adjust your color profile

go to system preferences/ display,
then in the "color" tab, select another color profile
(you might need to uncheck "Show profiles for this display only")

Hi, Thank you both for your response.

Just for futur reference, I have a Epson EX3210 DLP 800x600 2700 lumens.

@sigmasix : Ok I understand it more, but when I see (and its one in a hundred) something like that :
http://vimeo.com/33808238, I believe its achievable to have a "real mask" or "real black" .. no ?
Maybe its the quality of my projector...

@franz : I've played with both the settings on my projector and the color profile preference on my mac, but It's always "on".
I've put just a black background, and even in daylight i can see it...so imagine in complete darkness..I would end up with a
'rectangle of light' around my animation.....

the video you linked has been color corrected so it's easy to change this grayish part to real black.

I think epson is the worst brand for this kind of problem… I had one long time ago and it was a nightmare. I assume it's a LCD you have, mine was LCD but now it's in the cupboard eating dust haha!

By " color corrected" do you mean corrected on the movie he made of the installation ?
Like if we were to be there, it wouldn't be pitch black ... ?

yeah, the video has been edited before being posted to vimeo. If you were seeing it for real you would have seen the grayish of the projector. Probably less than with your projector, but it was definitely there.

Thanks @sigmasix,
So what would be the basic workflow or settup to minimize this unwanted effect...
I can't believe every video projection I see online is post-edited... so there most be
a solution. Maybe its the projector itself, in that case, what would be the minimum
requirement (ratio contrast ?) to buy a quality one...

Any advice or experience is well appreciated

your projector is not high quality. to minimize the effect, you can reduce the brightness.

If you were to buy a new projector, look for the highest contrast ratio.
No projector is perfect.

Thanks @Franz.. I search a lot before buying a projector, but since i didn't had a big budget
I choose something to experiment... but If I would have known I would have choose something
better.. I didn't know it was the contrast-ratio the problem. Still, the spec says 3000:1.

Anyway, thanks again, now I know what to do.

Exactly! The problem lies on the quality of the projector. Points of contrast is the value you should seek when renting or buying. http://www.barco.com/en/products-solutions/projectors/large-venue-projectors/20000-lumens-1080p-hd-three-chip-dlp-projector.aspx?tab=specs is a good option for large venue or else seek for values over 2000:1 points of contrast.