Tag Archives: canon

Cambot pt5

Continued from: http://bradisdrab.wordpress.com/2013/04/30/cambot-pt4/

I haven’t been 100% satisfied with the movements I’ve been getting from the Pan/tilt head so far. Its promising, but there is some play in the parts which introduces some counterbalancing and wobble. That and the motors turn a bit more quickly than I’d like, which makes small, controllable, incremental, movements a bit tough.

Time to take it apart and rebuild.

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I couldn’t get good results with my hand drill. It was just too sloppy, I needed a better way to do it. I wish I had a milling machine, a full machine shop would be amazing, but I can make due, and make whartever I need.I tried pricing out mini milling machines, but they are just too expensive, instead I looked into small drill presses. I found one for a good price and Kyle and I put it together with a vice and the cross slide and rotary table, I had been using as the camera mover previously. I ended up mounting the whole thing to a metal stool I found so it can be wheeled around the shop. Totally custom and it works great.

My custom mini mill drill press with fricken LASERS

Thankfully getting better tolerances from this drill press. The right tool for the job. Cambot is reassembled, now with everything fitting together much tighter, and swapped out the motor in the pan for a slower one.

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The basic blocking for Cambot’s pan and tilt is finished and working, so I’ve started planning and working out the mechanics for the next two axes. The first of which is pictured above, the rack-focus. This is likely the easiest of the axes; simply a pinion gear mounted to a mini robotzone gearmotor, which will fit with the len’s focus wheel’s teeth. I mounted this motor to a little arm attached to the 15mm rails on the P/T head, so it will remain adjustable for different lenses as well as remianing in position with the camera.

Next comes the Jib, it needs to be able to crane up and down. The Jib is well counterbalanced so won’t need a lot of torque, but with nothing there at the moment it tends to drift slowly.

Drilling out for bearings on a jib motor frame for #Cambot. #moco #drabfuture

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I spent awhile thinking about ways to hold that axis, and looked at a lot of options, eventually deciding on a timing belt. Also I learned that parts can be ordered in bulk to save money from ebay, so I picked up a bunch of timing pulleys, and bearings. Unfortunately they weren’t as easilly matched as the parts I got from Servocity, so I had to do a bit of work on them to get them assembled.

Bearings and timing pulleys mounted to frame. #cambot #moco #drabfuture #motioncontrolcamera

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I fit two idler pulleys and one to drive the belt. Looking pretty slick now, just needs a motor.

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Here you can see how the belt will feed in with either end leading back to the Jib arm on either side of the axis.

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With 4-axis nearly in play, and two more on the way, I’m going to have to start thinking about how I’m going to control this thing. My current testing methods the MX2 and can manage 2-axes at a time

This new MX3 from dynamic perception looks interesting, it can control 3 axes, and includes a MoCobus port which could be very promising in the near future, afterall I’ve been loving the Mx2.

My other option is to customize something from scratch using an arduino. I’ve been pouring over tutorials and it actually sounds totally do-able. I’ve been calling that “The Magic Box”, basically a controller that does anything I want/imagine, from stop motion, to live control and follow modes, with programmable control of dynamic lighting, and the ability to import/export 3D camera moves from the computer. One can dream.

Gotta walk before I can fly, so far I’ve learned how to make a led work.
Learning about micro controllers. Finished the first six tutorials; Blinky lights, buttons, knob.  #Arduino


‘Reverse’ IBL

I watched ‘Beyond the Black Rainbow’ last weekend and put together this test video,

This weekend’s tests were all about getting brainstorming on ways to improve Cambot and doing a bit of shooting in the studio. The studio time definitely helped to see what is working on Cambot and where it can use some improvements. The goal of my shoot was to experiment with lights.

I’ve spent some time before working with traditional Image based lighting, where I basically used a reference image from a location to digitally light a 3D model.

IMG_3864

The reference image is typically a panoramic image unwrapped from a photo of a chrome sphere. The chrome sphere reflects a full 180 degree image of the reflection and in doing so the reflected light which would be cast upon the object. Typically a gray sphere is photographed at the same time for comparison with the in-progress/finished model.

IMG_3868

I want to begin the same way, background locations photographed with reference spheres, then I want to photograph practical scale models to place in them. Typically this is achieved by attempting to mimick the lighting conditions, i.e. “the sun was here so we place a key light here, with a fill light on this side and…”. Then through a process of ‘match-lighting’ a cinematographer/Director of photography can reproduce the location’s lighting.

Why ‘Reverse’?
Now I want to turn this all around. In theory by using these reference images it should be possible to recreate the environment lighting on demand when photographing a practical model or actor. All that would need to happen is for a directional light source to project onto the surface of the model with the same hue and intensity as the reference.


This definitely isn’t a new idea, Paul Debevec, developed this years ago through ICT with his lightstage, pictured above, which I’ve linked here rather than attempting to further summarize it;

My approach is through the use of DMX stage lighting. There are multi colored lights capable of mixing Red Blue and Green in real time. These are also programmable via DMX512 protocol, so they can be set up to run through pre-set lighting configurations.

My Stage
I’ve been using these slimpar 64 RGB LED lights from Chauvet. I’ve currently arranged five of these in a half ring around my stage all pointing inward.
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I plan to eventually upgrade this to a more automatic solution. There are a lot of software packages designed for stage techs, in fact many concerts and night clubs use these systems. There is also computer soft/hardware solutions more designed for filmmakers and animators like this card for Kuper which fits in with a Kuper motion control system. Or the DDMX-S2 from Dragonframe, which allows stop-motion playback control for incremental programs. For now I’m controlling these via the Chauvet Obey-10 mixing board, which allows me to set sliders for each of the color channels of the lights independently.

What I’d really like is for it to be able to process a ref image or video and reproduce it automatically, or use a video clip and essentially ‘play it back’. It makes sense that through software I could take a reference image and sample the quadrant’s hue and value, and route that into a DMX controller, then those values could be used for control of the lights.

The Science
The theory sounds great, but first I have to figure out the physical lighting limitations of this rig and about LEDs in general. I’ve often been warned about color temperature in photography. The difference between Tungsten (3200K), Daylight (5700K), and Fluorescent (4000k). However in attempting to get a clear answer to the temperature of LEDs I went down a rabbit hole. It seems this all goes out the window the moment you start color mixing. It is completely variable, which means it could be anywhere. Added to this LEDs typically have a more limited spectrum, take a look at

these graphs;

LEDs are often assigned a CRI which as I understand it, is how well they can reproduce the sun’s light, and thus how balanced a color will appear when illuminated by it. The other thing I’ve discovered about LEDs is the pulse width of the lights themselves. They aren’t actually constantly on, the light blinks on and off at arate so fast we can’t detect it. For many lights this is slowed down for the dimming feature/effect. This pulse width modulation which our naked eye cannot detect, even at lower frequencies will be detected by the camera when set to a high shutter speed.

I found it really interesting in this test to see the way the light’s wavelengths interacted with the shutter speed of the camera. It seems there are ways to work around it, selecting a lower shutter speed for example, but I haven’t quite figured out the science for it. Looking over forums shooting around PWM seems to be an increasing problem, especially for venue/location photographers;
Shutterspeed and flickering hmis
PWM is not your friend
LED flicker on camera


Air Mortar pt2

This is a continuation of my post here I sealed the leak, started using a more compact bike pump, and triggering it via the electric valve for these tests;


Air mortar pt1

I need to create some explosions for my Drab Future project and won’t likely have access to pyrotechnics, so I’ve got to improvise. I’ve seen plenty of great tutorials online, so I’d like to see what I can come up with myself.

I shot this video while I was testing out ways to create more practical effects on set, this is just the first test with the air-mortar rig, which is a lot like a spud gun. I’ll be doing more tests very soon…

Below are more tutorials that are in line to what I’ll be trying…

Air canon/mortars (these are Not mine, just posting as reference/tutorials)

Simple-Set-mounted-PVC-Blood-Cannon
Guacamole_Gun
indietalk