Results 1 to 10 of 10

Thread: Time Slice rig trigger challenge

  1. #1
    Join Date
    Aug 2008
    Location
    South Devon
    Posts
    349

    Default Time Slice rig trigger challenge

    Here's a tricky one .

    I need ideas on how to trigger a time slice rig at a particular time, the shutter release has to fire off all cameras the microsecond that a gun is fired.

    I've run some trials on my rig today. Ok, fine, plenty to do to tune it, but heading in the right direction, I tried it with just six cams, enough to identify what needs to be sorted.




    One of the things I want to film is a little video article about Field Target Shooting, another hobby of mine. And I want to expand the time slice thing to the 'bullet time' variant to include a travelling 'bullet' in super slomo whilst the time slice effect is occurring. Nothing new there, same-oh thing that we've seen before, but at least this is an element in a structured film, rather than for the sake of it, which is what seems to be around the most.

    So, the scene is our target shooter with his Carlos Fandango Rifle in a typical standing position, like this:



    In an ideal world the background will be a total black, so I'll be trying my hand a green screen. The shooter will bring the weapon down to aim, and the time slice will start as the rifle is fired (these Pre Charged air rifles do show a marginal muzzle blast in some conditions, but I'll create a slightly more visible synthetic one with a little talc or chalk powder in the silencer, for the record this type of rifle can be fired without a load ['dry fired'], but not too many times).

    At the same time a 'pellet' will be leaving the barrel, the view arcs around to the point just past the firing line to the last time slice cam (there will be 24 cams in an approximate 90 degree arc, so about a second has past). The camera will then switch to live video which pans to follow the pellet as it passes real close and on to the target, perhaps the video cam will follow the pellet all the way to the target.

    Ok, so, how do I time the shutter release to the muzzle blast? At the moment all I can think of is a microswitch on the gun trigger, positioned so that the trigger discharges the gun then hit's the switch, which should give enough time to eject the powder, it is all microseconds though.

    Unless someone else can come up with something?

    For the record, I've given myself a year to suss this video.

  2. #2

    Default

    At first I thought use some kind of sound trigger, but I think the lag would be too long. Sound travels about 1m in 3ms so it your trigger mic was a metre away the pellet would probably have left the zone covered by your cameras (I suspect - I haven't actually done the maths)

    So I do think a microswitch might be the answer.

    Did you get your sequence firing circuit from the pervious request?

    The other option I can think of would be to fake it in a 3D package, Andrew Kramer has a tutorial DVD called "the bullet" which does pretty much what you want, I think... But of course it's all fakery, and how cool would it be to actually capture the real thing (even if, I suspect it wouldn't look as we are used to seeing from that kind of shot)

  3. #3
    Join Date
    Aug 2008
    Location
    South Devon
    Posts
    349

    Default

    There's no chance of actually capturing the pellet itself, they travel at 700 feet per second plus, so the pellet bit was always going to be CG, it's just the muzzle blast I want to capture in the time slice.

    I've read one suggestion since the OP, originally used for flash photographing bullets going through things like bottles and fruit, this uses two layers of tinfoil with a tiny air space between them. In effect this is a switch as the two layers are wired to the flashes release (shot in the dark with the camera shutter open), when the bullet hits it shorts the two layers hence 'making' the contact. This may be worth trying, naturally the foil 'switch target' shall we call it needs to be behind the line of cameras, and it'll mean shooting between the cameras as I want to go past the line of fire. That's ok to do and a safe setup can be arranged. Worth a go I think.

    No response for a sequence trigger from here, but on a totally un-related forum a guy who designs control circuitry for machine tools suggests it's 'not a problem' and he's working on a circuit diagram for me to make it up. He explained about this IC and that widget etc, but whilst I can follow a drawing when it comes to electronics the reason why it's actually working is a black art to me, electric sting has never been my forte, so imagine what it was like getting the control unit for my current system together, and this pic was taken only about a third of the way through! Off the top of my head there's about four hundred terminations in total on the finished thing for just twelve cameras!



    Work on the fifty camera rig has just started .

  4. #4
    Join Date
    Nov 2005
    Location
    Bristol uk
    Posts
    8,938
    Blog Entries
    1

    Default

    Jerry - wow - that is so cool. I often think about trying to do time slice on the cheap - but even cheap ends up expensive.

    As for triggering - and I havent read in detail - my understanding is that sound is the usual methind.

  5. #5
    Join Date
    Aug 2008
    Location
    South Devon
    Posts
    349

    Default

    Thanks Mark, it's coming along.

    Here is the panel as it is now, all the terminations made to the circuit board. I could have gone straight to the switches with a lot of it, but the need for 24 diodes (visible on the circuit board in the pic above) to stop back feeding was easier to manage by using a kind of termination board.

    The whole control panel design need not be this complex, but I wanted to be able to power up, exposure lock and release each camera for setting up, once done the 'Arm' switch joins the camera to a common rail so that the 'all fire' switch releases them all, a remote swtich is yet to be fitted that can be triggered by a hand held or other switch, such as I might use for the gun shot.





    Here's the front of the panel at the moment, power supply fuse holder, and remote switch socket yet to be fitted (the remote switch could also be used as a link socket so that multiple panels can be triggered at the same time).



    If you do ever want to build a rig, speak to me, I've learnt loads that could save a lot of time, and information on the net amounts to not very much at all, I've had to suss a lot of it myself .

  6. #6

    Default

    Why not do the whole thing in CGI. Take the camera shots of him firing, then create you own muzzle blast and pellet action in CGI.

  7. #7

    Default

    Or (if your actually firing), lazer pointer shining down past the barrel to a photosensor with an amplifier and an edge detector.

  8. #8
    Join Date
    Jan 2005
    Location
    Warsop, Nottinghamshire.
    Posts
    4,465
    Blog Entries
    2

    Default

    Quote Originally Posted by MrFluffy View Post
    Why not do the whole thing in CGI. Take the camera shots of him firing, then create you own muzzle blast and pellet action in CGI.
    I think you're missing the point here. The challenge (as far as I see it) is to build a rig that works. The fact the first project happens to be firing a gun doesn't mean the next project will be. I think if the rig is perfected, the possiblilty of hiring it out would be boundless. I just wish I had some expertise to help the project along....

  9. #9

    Default

    Well I think the problem here maybe one of what it trying to be achieved. When photographing a baloon breaking due to a gunshot its done in a darkened room with an open shutter and a strobe fired at high speed to capture the action. Because the shutter is open there is no shutter lag that will occur when shooting in daylight. So the whole thing is practically instant after the triggering of the flash.

    Thus to do this in daylight will need some form of predictive shutter release.

    Of course you could do it by setting all the cameras to burst mode, shouting action, and hoping for correct timing, and doing it several times.

    I have often photographed people jumping and its not too hard to get them mid jump using flash, but capturing a bullet would be a lot harder because of the need to predict the release point.

  10. #10
    Join Date
    Aug 2008
    Location
    South Devon
    Posts
    349

    Default

    To aid this then I'll make the target clearer:

    The aim is to capture the moment when the muzzle blast occurs (as slight as it is)
    The gun will be dry fired, no pellet.
    The pellet would be put in using CG.

    The rig is now fully functioning, basic trials are done, just need to clarify some of the processing needs, and I'll be ready to have a go at this.

Similar Threads

  1. Image manipulation for time slice (Bullet Time0 - Premiere CS3
    By Jerry Hill in forum Adobe Premiere, Premiere Elements, and After Effects
    Replies: 2
    Last Post: 09-03-2008, 10:40 PM
  2. Challenge - chontest.com
    By choober in forum Pimp the Link
    Replies: 1
    Last Post: 04-08-2008, 09:23 PM
  3. How to slice in detail the time line is too small
    By pielcanela in forum Sony Vegas video editing apps
    Replies: 4
    Last Post: 10-04-2007, 10:55 PM
  4. A bit of a challenge!
    By fastedit in forum Adobe Premiere, Premiere Elements, and After Effects
    Replies: 4
    Last Post: 01-01-2005, 10:59 PM
  5. BBC one minute challenge
    By purejammy in forum Forum Announcements and News
    Replies: 3
    Last Post: 08-04-2004, 01:52 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •