This is not a regular forum post, it's almost a tutorial! So thankful we have guys like you here!

best

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no IR light hits the floor. to do this right, you need to get your profile as low to the ground as possible and shutter off the floor.

ideally, i use a 50degree source4 junior in each corner of the stage. never faded up more than 40 percent.

projectors generally don't emit much light in the infrared frequencies, so i've never had to filter a projector.

LED lanterns don't emit much IR light, but regular theatre lighting has loads (feel how hot the lanterns get after a few minutes) so any light that is focussed on the floor will effect your tracking.

this setup will work best when the only visible light is from the projector.

effectively i buy this morning this :

"Neewer 52mm Filtre Infrarouge 720NM IR720 Pour Appareil Photo Reflex Numérique Avec Un Objectif 52mm Canon Nikon" from amazon to put on the camera's lens .

i have built the system and everything seems to work fine but i would like to have some some advice for :

- correcting the lens distorsion ( 2,8 mm security cam ) : the camera is a about 6m higher to cover a 6m by 6m dance area.

is there any actors to do that ? for matching the coordinate to the real world? 

- where is the best place place to put the IR emitter ( i switch off the ir led of the camera and put a PC with red/blue gels exactly on top of the dancer to avoid shadow ) ? as everyone say to put it in the back os the stage ? 

- i have no problem to track one or two dancer in the dark  with the actors method of vjsculpture ( effect mixer and freeze) .

 But the ir tracking system is attached to a processing patch witch interact with the coordinate of the dancer . 

When i project a video on the top ( videoprojecteur is placed exactly the nearest the camera)  i have some difficulty to cancel the video projection from the video feed to "eye" or "eyes ++" ...the eye actor seems to doesn't know what is the dancer and what is projection on the floor .

I notice that the floor is a white carpet . 

I didn't put a lee 73 filter to the camera , is this will help ?

is there a patch example to follow to cancel the video projection for not be seen by ir camera ? 

moreover the lens distorsion doesn't help ...

well thx for your reply ... 

I have used security cam with IR light(nightvision) with MXO2\. The latency was just few frames(out of 30fcp) almost instant. The security cams are getting obsolete so fast that it is possible to get a good one for very little money second hand. Look for TV-lines - the higher the number the better is the picture quality.

But I have done a setup with hacked(IR filter removed) Sony Eyecam PS3 as well where we illuminated the background with IR, so the subject become as a shadow. PS3 is USB camera with great quality and very little latency. Only problem is the length of USB cable(you need an active(powered) extenders going over 3m).

Usually machine vision cameras (also meaning expensive) have high sensitivity for IR- much more than security cameras, and hence get you better detail as well as faster frame rates and lower latency, but they are not possible to use in Isadora, you would need to feed the image via syhpon or spout, or use other tracking software and send the data over OSC.

As for span, pretty much any camera you will be looking at will have a removable cmount lens so you can get pretty much whatever area you want, but remember as you get wider lenses you get more distortion (fish eye) and the coordinates will not exactly match up.

Check these post for more details.