TLA – First Test Video

Got the unit up on tripods this weekend, and took to the parking lot out in front of my studio to take some test videos.  Even at 9am, the heat is rough, the first day shooting around 2pm I had to call it early, given that it was about 110F on the concrete in the sun, and I just wasn’t up for being out there.  The first test indicated that post-shutter delay before motor movement was essential, so I spent a few minutes enabling it in the UI (it was already enabled in the motor control unit, just no way to set it up) and got to test it again on Sunday.

Well, the test went ok – I found some serious design flaws with the trucking motion, primarily that I didn’t use an anti-backlash nut, meaning that the slop in the flange nut I used was enough to pretty much eliminate all possibilities of movement horizontally when moving in such small scales.  I have some vertical lift in the imperfection of the two ends of the drive rod, so the only captured motion was a slight circulation up and down (I did allow for vertical motion elimination through a slip cut into the attachment bar for the cart, but the new design of the cart used a shorter angle bracket, eliminating pretty much all of the vertical slip capabilities) due to this lift and the backlash on the nut.

My calculations as to what was a “reasonable” pan movement degree range was largely based on the use of a wider-angle lens than what I used for this test (see below), so it’s not going to allow for very slow movement with even a “normal” F/L lens.  My assumption about skipping motion between shots also doesn’t play out well, at least I think it doesn’t, as the video shows below when it switches to once every other shot.  Moving every third shot makes it even jumpier, so I may just eliminate that feature all together, and instead re-gear the pan motion to something closer to 9:1.  I’m not looking forward to re-building the top plate of the cart again, but it shouldn’t be a huge deal.

I’m not certain that it’s going to be field-ready at this point before I leave for Big Bend, but maybe some new tests and an anti-backlash nut will make it pan out.  (That’s a very little joke, see?)

So, for the video specs:

Camera: Pentax K10D

Lens: SMC-A 50/2

Motion Control: Panning approx. 0.07 degrees between each shot, and then moving to the same movement every other shot about 3/4ths the way into the video

Shot Interval: 1.5s

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~ by c.a. church on September 2, 2008.

4 Responses to “TLA – First Test Video”

  1. Hey hey! Nice one. Well done!

    As you say, you’ve found some problems now that you’ve run it up – but that’s exactly how it goes. You’re in the refinement process now when you can SEE the fruits of your labour!

    Have you thought of using a ‘b’ setting on the shutter to avoid that flickery look? Even a few seconds would I guess blur out a lot of the rapid motion in things like leaves etc.

    I was thinking about how to do this with video – probably post processing it (very long winded) as my camera (DVX-100) can’t shoot at very slow shutter speeds.

    [m]

  2. I’ve also been dreaming about being able to specify a measured point in relation to the track so that the arduino can do the math itself about centering the field of view on the target object as it rolls by. 😉
    [m]

  3. Just been through your entire blog. I’m exhausted! Well done on everything so far. Thank you for documenting all of your progress so thoroughly. I’m inspired to do the same with my DIY Motion Control rig. Good luck with the rest of the project. I’ll be watching via RSS with a keen eye 😉

  4. Hey Dan! Thanks for coming by – I spent a good bit of time on your blog as well, I appreciate that you’ve taken the time out to write up details as you go along. The tutorial will help to reduce how often we have to answer questions over on the arduino forum *grin*

    I’ll make sure to keep on posting as I go, alas, this coming week I’ll be in the desert, so don’t expect much here until the 6th, then there’ll be a nice trip report and hopefully some videos!

    !c

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