[ANSWERED] Infrared tracking from above

mark_m

Hello all,

I'm looking for recommendations for a decent quality yet inexpensive IR camera which can be run from mains electricity and which can - preferably - output a digital signal, preferably SDI or HD-SDI.

I'm working on a fascinating project at the moment for the Welsh NoFit State Circus (for whom I used to perform, in a previous life!), where we're projecting in the round onto their circular stage using four projectors at 90 degrees to each other. That complex mapping's being done by someone else using MadMapper, and I'm tasked with creating content (which we'll feed to MadMapper using NDI from Isadora).

Since we'll be projecting onto the performers themselves, I wanted to do IR tracking so it's not affected by visible light from the projectors.
I've tried using Mark's IR tracking method, so lighting the floor not the wall, but it's proved difficult to cover the stage in IR light without also catching the performers.
We've had some success using IR torches (flashlights) incorporated into performer's hats and pointing up at the poor quality hacked security camera we have in the roof, but I feel that the resolution's not great (I think it's like a quarter NTSC!) and it has an analogue output. (I'm having to use an analogue to digital device to convert for the computer's capture card to see. One more thing to go wrong).

So... if anyone can suggest anything? Happy to take a security camera apart and bodge the IR pass filter if necessary, provided there are clear instructions to do that on YouTube or somewhere!

Price is, of course, a consideration. Don't think we can spend more that a couple hundred pounds / euros / dollars.

Thank you all!

Mark (like Jonah, in Wales).

Fred

@mark_m for a.cheap solution there are lots of SDI 'security' cameras like this https://www.ebay.nl/itm/HDC-HF...

These cameras have a full manual mode but they are not precision devices.

You will need a lens, but that means you can pick something wide enough to get the floor from a flexible height.

You will likely want an IR pass filter, not having one will likely be adding to your lighting difficulty, and this will probably cost as much as the camera but make a huge difference, check Midwest optics and make sure you get the correct wavelength for the IR lights you are using.

There are also some high quality IR lights that will let you do a butter job of lighting, not cheap stuff though.

dbini

hi Mark,

bear in mind that most modern CCTV cameras will have IR blocking filters installed, thus making them almost entirely useless for your needs. before buying a camera its best to check with the supplier/manufacturer that it doesn't have IR blocking. unless you feel confident enough to take one apart and cut out the filter.

The method i've always used for overhead tracking is the opposite to Mark's method - for the NFS stage I think you could use 4 wide angle profiles mounted as low to the ground as possible and shutter the light off the floor (also make sure its not spilling directly onto the camera). focus them and then drop in your IR pass filters (red green & blue gels) this should give enough coverage for the whole space to light the performers, but not the floor. i find that this gives pretty accurate tracking, even with a low quality old b&w CCTV camera. with this method you need to be careful how much natural/halogen/LED light is hitting the floor, so it works best when you only use projector light or nicely-focused shins.

Have fun in Cardiff. shame i'm not still there, it would be great to catch up with you again...

john

Fred

@dbini @mark_m I would actually suggest the opposite, consumer cameras have IR blocking filters on them, CCTV cameras are almost all desinged to work with IR lighting systems. These cheap box cameras have a solenoid that moves the IR blocking filter in front of or away from the lense when you switch it from day to night mode, so they can be used with IR illumination in dark sapces. I have seen this even in sub €100 cameras, it is not a fancy thing.

dbini

@fred
thanks for clarifying Fred, i guess i was talking about more industrial cameras - particularly the ELP USB cameras. i wouldn't recommend these, despite being small form and a good price, the lag is unpredictable.

CitizenJoe

Other cameras that work are Sony camera with "nightshot". Old ones are available on eBay for next to nothing. Put a Lee 87 filter in front of the lens:

For lighting I used a similar set up to @dbini - a typical dance "Shin" wash with the light cut off the floor and the RGB gel package in front. I'm not at home, so I can't access my notes, but it was something like 2x Lee 119 + 1x Rosco 91 + 1x Rosco 19. @mark may remember - I learned it from him a long time ago... Be sure not to run the lights too high!

If I were to do it now, I would try something different with LED IR emitters. I wonder of there is a way to make LED ellipsoidals work?

Cheers,

Hugh

dbini

@citizenjoe
I have a few LED IR floods, their wavelength is great, but they are designed for flooding outdoor spaces so CCTV cams can see everything. they are really difficult to control the direction of the IR because every little LED acts as a wide angle light source. They seem to work best in small spaces, and i build each one into a little wooden box to mask the IR off of the floor.

CitizenJoe

@dbini said:

<p>@citizenjoe i build each one into a little wooden box to mask the IR off of the floor.</p>

I was trying to do the opposite: keep the light on the floor and off the dancers. The wooden box is a good idea - like barn doors!

Cheers,

Hugh

mark_m

@citizenjoe @dbini @Fred

Thank you so much all of your for your suggestions / advice, recommendations, and shared experience.

You've raised some really interesting questions about method - IR light stage or performers, for example.

I'm going to go and sit in the tent with the lighting techs and the riggers and ponder the variables, and will report back.

Thanks again!

And John, would be great if you with us in wet, windy Wales, on an industrial estate near Llantwit Major!!

Cheers Mark