IR camera advice - which type to buying ?



  • hi everyone ,

    I am looking for advice to buy an ir camera . i manage to build  an ir tracking system on top  for a dancer .
    The video will be coupling to :  blackmagic intensity shuttle or an matrox mxO2 or blackmagic ultrastudio mini ....which one provide low latency ? .
    what model to buy according that the camera will be at 6m higher for covering an aera of 7m by 7m ? our amount of money will be between 70 to 130 euros .
    i am based in france .
    the IR tracking will be the only use of the camera .
    Do we have to buy extra IR projector ?
    thx a lot for your advice ...


  • To be honest your budget is low, but not impossible. 

    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.
    http://troikatronix.com/troikatronixforum/discussion/comment/10338#Comment_10338
    http://troikatronix.com/troikatronixforum/discussion/comment/10801#Comment_10801
    Fred


  • It depends how much detailed tracking  you need(as Fred points out too).

    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).


  • thx a lot for your advices .

    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
    Normally the video projection should not be seen by the ir camera ? 
    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 ... 


  • you need to filter out visible light from entering the camera - this will prevent it from seeing the projected image. so yes - you need some kind of IR pass filter - either something from a security camera or floodlight - or a combination of dark lee filters. thats one reason to use IR. the other is so that you can track your dancer in the dark. a single lantern directly overhead, filtered to only emit IR light, will not be useful (unless you want to track the dancer's shadow) - you need contrast between dancer and floor. i use profiles on floorstands, shuttered off the floor, to create a white shape of the dancer against a black background. (un-illuminated floor)



  • thx dbini for your reply .

    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 .

    do you think , i need to put "heat shield" gelatin's to put on the video projector's lens ? some say video projectors still have a dichroique lens which stop IR frequencies some say no ...well ...
    i will try to use profile on floor stand on each side of the stage ...do you try with the IR emitter on the face/floor .
    question if i use a PC or profile  on top/center there will be no shadow ?
    do you thing the with carpet reflect IR light ?
    thx  


  • this is how i focus the profiles (you have to focus them before adding the filters, because afterwards you cant see anything)

    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.

    670558-focus-ir.jpg



  • Great answer @dbini!

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


  • thx a lot @dbini ...i will experiment your recipes in few days on a real stage ...


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