Tuesday, June 22, 2010

Tips for the CMR Blackbird

It took about a week to learn how to fly the CMR Blackbird.   With this post I'll try to list down what I've learned in the hopes it can be replicated by other people.

Learning to Balance
It's like riding a bicycle.  Explanations can only go so far.  It has to be experienced.   But I think I have tips that will get there faster.

  1. Level set your expectations, you are looking for reduced motion.  It might not be perfectly still like a dolly but stable enough not to cause nausea.
  2. Find your camera's center of gravity by feel.   Put your finger on the bottom and find the place where it least topples.  It's like finding the balance point of a plate with a cupcake on one side.   You can use a pencil under a camera plate to help you find it.
  3. Side to side balance is priority when centering as it will have the most tendency to be visible in footage.
  4. The Blackbird's bubble level isn't very accurate.  My Canon 7D has an electronic level that gives great feedback since its at the very center of gravity.  But that's the only camera I have that has it.   The rest need an external level.  A substitute would be a spirit level designed for the cold/hot shoe.  It's closer to the center of gravity for the camera and should therefore be more accurate than one ones mounted on the corner of a stage. 
  5. The bubble levels are a guide, you need to develop a feel for balance.   When I balance I make it front heavy, then back heavy until I find the mid point.  I have to be patient until I can be instinctive on how close I am to the most stable point.   I do the same for the roll (left-right) component.   Be sure to have the T-Bar extended all the way so the rig will be sensitive.  While it's sensitive it's easier to see if the balance is off since it will teeter.  You may never seen it completely still.  This is fine as YOU can compensate for it with your left hand when you fly.  You can also use smooth touch to cheat.
  6. Drop time of 2 seconds is a good start.   I set my T-bar to 22 to achieve this.   Why 2 and not 1.5?   It's easier to count whole increments that half.   Use a stopwatch or a watch with a seconds hand to time it.  Counting "One Mississippi" may not roll off the same way for everyone.
  7. Trust the Blackbird to do its job.  The rig may seem to teeter constantly, but that does not necessarily show up in the footage.  I've learned that when I see the Blackbird teeter constantly, it's actually compensating against ME!  When I review the footage later it shows shows smooth action.

Stable flight

  1. Wind is the enemy.  Find a way to block a breeze when you can.  If you need to see how easily it can be influenced by wind, set the rig in front of an air conditioner or electric fan.    Outdoor wind may be stronger.
  2. Use two hands.   The left hand should lightly touch the gimbal.  This is the toughest part of learn as you have to discover by yourself just how much pressure is appropriate.   For me I only apply pressure when I want to turn it.  Most of the time I'm just holding it while trying not to get in its way.  See how hard it is to describe?
  3. Use the same shoes when flying.  I have a pair of waterproof Merrel shoes that I take with me everywhere.   The cushion isn't as soft as my Nike cross-trainers but it's the shoe I'm most likely to have on when I'm actually shooting.  You need to get a feel for how the ground affects your step while flying.   Your legs, especially when bent, will absorb a lot of shock that would otherwise transfer through your arm into the rig.   If you keep the same shoes it will be easier to guess if the ground is too hard and you need to step a bit more lightly.

Securing Parts

There are three parts that constantly loosen on my Blackbird that need to be secured.

  1. Tighten the gimbal to the stage.  When I do pan motion or hold the Blackbird between takes I tend to hold it by the neck of the gimbal that attaches to the stage.  This tends to unscrew it thus changing the height of the balance point. 
  2. The lower fastening screw on the T-bar tends to loosen especially after the bar hits something.   Make sure it's tight after picking it back up to use.
  3. The rubber shoe on the resting stand comes off.   Secure it with a tie down.

Sample Flights for Reference
I wouldn't call these examples of a perfectly balanced rig but the footage is usable.

Indoors, walking, shot in 24fps

Outdoors, running and walking, shot in 60fps, slowed down to 24fps

Tuesday, June 15, 2010

Editing Canon 7D with Blender 3D

So I went on a trip without my editing rig.  No way was I lugging a quad-core desktop on my trip.   Instead I'll do rough cuts on the field with whatever machine I can borrow.   Unfortunately I had my Vegas and Cineform license information was locked away on a powered-off hard drive half the world away.  Windows Movie Maker wasn't going to cut it.   In comes Blender 2.49 and Super(C) to tide me over.  My purpose was to do rough cuts to see if I had enough footage.

The Super(C) is free software that will let you downgrade the high-bit rate H264 video from the 7D to AVI format with a codec of your choosing.  I selected and IPod-like format: MP4 with 6Mbit in AVI format at 480x272.

Tutorial on how to use Blender as an NLE

Switch to Sequence Editor
-> (upper bar) SR:4-Sequence (default is SR:2 - Model)
Set Clip settings
-> Format (lower right) -> change to whatever size you want to edit (there are presets like HD and FULL on the right) -> FPS: (change to 24, 25, 50 or 60)

Load a video
-> (middle-timeline window) -> use scroll wheel to unzoom the timeline (timeline is in frames) Shift-A -> Movie+Audio (HD -- stands for Hard Drive not High Definition) ->  Search for your clip on the hard drive -> Drag the icon to the frame marker you want -> Audio track is above Video, may not synch if FPS is wrong

Undo a grab or any operation

Grab video (to move clip around)
Shift/Right-Click (to select track),G -> drag the clip around -> the left side is the leading frame count

Cut a clip
Use arrow keys or left-mouse button to scrub the green vertical bar to scrub to the point you want to cut -> Shift/Right-Click (to select video track) -> Point to right-facing arrow at beginning to track  (or left-facing if cutting from end of clip) -> G -> Drag left or right to the green vertical bar you previously set -> Left-click to set

Cross-Fade Transition
Right-Click (to select track) first video that is the start of transition -> Hold down Shift -> Right-Click (to select track) of second video -> Shift-A -> Gamma Cross -> drag the gamma cross transition to a track number above the two clips

Change Last Frame
The third window down defaults to 256 (frames), change this to the number indicated on the last clip on your timeline so you can display the entire movie

Save Project
File -> Save -> Navigate to directory you want -> rename untitled.blend to any name you want -> Save As

Output to Movie
Change Q (Quality) from 90 to 100, Change format from JPEG to FFMPeg (or whatever format you want) -> Video -> Choose the Codec (MPEG-2 by default, H264 is available) -> Audio -> Downsample Mix -> Output: Change the output directory from /tmp to wherever -> Do Sequence -> ANIM -> Wait for the Animation to finish

Take note how I use the word Animate.  There is a Render button in Blender.  It serves a different purpose from our normal NLE nomenclature.    In Sony Vegas we say Render.  In Blender it is ANIM(ate).