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MX2 Users Guide Part 3: Basic Use

The two basic motion control modes for the MX2 controller are Continuous Motion and Interleaved. (Also known as Shoot-Move-Shoot.)   In Continuous Motion mode, the motor moves irrespective of the camera being fired, and generally at a consistent speed.  In Interleaved mode, the motor only moves between exposures.  These two motion control modes can result in different aesthetics in your output video, and each are best geared to a specific type of shooting.  The following table will help to summarize the best way to choose between the two motion types based on the parameters of your shot, or the effect you wish to achieve:

Description Continuous Interleaved Notes
Moderate Speed, Short Exposure X   Can add a small amount of motion blur, and is easier to set up
Long Exposure   X If camera controls exposure, dial-in post exp. delay in MX2
Very Slow Speeds   X Used Fixed SMS to achieve motion over hours or days
Static Subjects, Medium Exposure X   Adds nice motion blur to otherwise static subjects
Static Subjects Sharp, Moving Subjects Blurred   X Set longest exposure time achievable
Star Scenes X X If moving with stars, cont. can help prevent streaking, but will reduce foreground focus on very long exposures
Critical Focus, Macro, or Long Lens   X Prevent movement when exposing

Now, many photographers will use a particular mode more often than another, as a matter of taste or artistic intent.  While the table above attempts to serve as a guide to when to choose between the modes, your workflow or shooting style may call for a specified mode that is in contradiction with the table.  Every one is unique, and their style is their own — you should practice with each mode and understand which is right for you.

You may only choose one motion type at a time, it is not possible to run one axis in continuous motion and another in interleaved.

Using Continuous Motion

The default behavior of the MX2 controller is to operate in continuous motion mode.  For the highest end of the speed range, the control acts as a basic Pulse Width Modulation driver, varying the speed of the motor by changing the frequency at which voltage is applied to it.  However, once the speed falls below the configured slow speed floor, a special “pulsing” mode kicks in.  Inpulsing mode, the motor is run at full speed for a brief period of time, usually on the order of milliseconds, and then shut down for a period of time.  This causes the motor to operate at full torque at absolute minimum speeds.  While the motor is only moving part of the time, the measured average speed over a period of time should largely approximate the inches per minute (or percentage of speed) specified.

In all continuous motion modes, you are able to choose from any one of 255 different speeds, from completely stopped to moving at full speed.  As each change to the speed is a 1/255th speed change, speeds will appear to make larger jumps when being entered on the main screen than you might expect.

At the very slowest speeds, it is generally preferable to move to interleaved mode, because the added vibration of the long pulses on the motor.

To enable Continuous Motion mode:

  1. [Enter] to enter the main menu
  2. [Down] to select Settingsand press [Enter]
  3. [Down] to select Motor Sl.Mod. and press [Enter]
  4. [Up] or [Down] and choose  pulse
  5. [Enter] to save or [Right] to abort

Using Interleaved Motion

There are two types of interleaved motion control available on the MX2: Calculated and Fixed.

Calculated Interleave Mode

In calculated mode, you input the distance moved in actual speed (inches or cm per minute), and the distance moved between each shot is determined based off of the exposure interval you input.  For example, if you input 1 inch per minute as your speed, and your interval is set to 1 second, the axis would move 1/60th of an inch between each shot.  This mode is used when you want to easily determine how fast you want to move from one point to another on the axis, and generally requires little forethought to set up a shot.

You may input values from 1/100th of an inch (or cm if in metric mode) to the maximum distance the motor can move in one minute.

To enable Calculated Interleave Mode:

  1. [Enter] to enter the main menu
  2. [Down] to select Settingsand press [Enter]
  3. [Down] to select Motor Sl.Mod. and press [Enter]
  4. [Up] or [Down] and choose  interleave
  5. [Enter] to save or [Right] to abort
  6. [Right] to return to the main menu
  7. [Down] to select Axis x and press [Enter]
  8. [Down] to select Fixed SMS and press [Enter]
  9. [Up] or [Down] and choose  Off
  10. [Enter] to save or [Right] to abort

Fixed Interleave Mode

In fixed mode, you input the distance moved as actual distance traveled between each exposure.  You may input values from 1/100th of an inch (or cm if in metric mode) to the maximum distance the motor can move in one minute.  This mode is used when you want to accurately dial-in distances moved between exposures, or achieve very smooth ramp (feather) transitions.   This is generally the preferred motion control method for extreme close-up shots and anything using a long telephoto lens to both prevent vibration during exposure and the accurately define motion from frame to frame.

To enable Fixed Interleave Mode:

  1. [Enter] to enter the main menu
  2. [Down] to select Settingsand press [Enter]
  3. [Down] to select Motor Sl.Mod. and press [Enter]
  4. [Up] or [Down] and choose  interleave
  5. [Enter] to save or [Right] to abort
  6. [Right] to return to the main menu
  7. [Down] to select Axis x and press [Enter]
  8. [Down] to select Fixed SMS and press [Enter]
  9. [Up] or [Down] and choose  On
  10. [Enter] to save or [Right] to abort

Manual Motor Control can be used to position the cart on the rail between moves.  Please note, however, that for very quick re-positioning of the cart, it is usually fastest to simply loosen on belt clip on the rail, pull the belt away from the pulley, and position the cart by hand.

Using Manual Control

While on the manual control screen, you can use [Up] and [Down] to adjust the speed of the motor, up to its max speed, and by holding [Left] or [Right] down, the motor will move in the given direction at the specified speed until the button is released.  To exit the manual control screen, press [Enter].

Note that in manual control mode, the available speeds at which the cart will move will range from about 80% to 100% of full speed, at lower speeds the cart may not move.

Actions:

  1. [Enter] to enter the main menu
  2. [Down] to select Manualand press [Enter]
  3. [Up] or [Down] to select the desired axis, and press [Enter]
  4. [Up] or [Down] to set the desired speed
  5. Hold [Right] or [Left] to move in the desired direction
  6. [Enter] to exit the manual control screen
  7. [Right] to return to the main menu

The MX2 controller can “feather” or ramp into and out of moves causing moves to start slowly and get faster within the video, providing a nice accelerating or decelerating effect.  It does this by altering the distance moved between shots, or the speed moved, starting with no speed and ramping up to your desired speed over a configurable number of frames.  Additionally, a lead-in or lead-out can be used to add a static period before or after a motor’s movements, adding to your ability to create the shot you want.

Ramp settings for a particular axis are saved between power-off cycles.

Configuring Ramping

A ramp into or out of a movement is done by changing the speed or distance moved based on the number of frames that have been exposed.  For example, I can set the ramp value for an axis to 24 frames, and at 24FPS output video it would take one second for the motion in the output video to come to full speed.  This is achieved by starting the motor at no speed, and then increasing the speed just enough to match the desired output speed at the right interval to reach full speed at the desired frame as specified in the ramp value.

If you also configure the max shots parameter for the camera, the MX2 will automatically ramp down the motor to zero speed so that motion completes when the max shots count is reached.  See Configuring Camera Control.

Note that in continuous motion mode, you only have 255 speed increments available, this means that ramps into low speeds (1-10% of maximum speed) can be rough.  To get extremely smooth ramps, it’s best to choose fixed interleave mode.  See Choosing Your Motion Mode for more information.

To understand how ramping will affect your output video, take the following parameter values:

  • Output video = 24 frames per second
  • Max shots = 240 (10 seconds)
  • Ramp rate = 24
  • Axis speed = 1 inch per minute

The following will happen in the output video:

  • For one second, the motion will accelerate to full speed
  • For eight seconds, the motion will run at full speed (1 IPM)
  • For one second, the motor will decelerate to no speed

This illustrates how ramping is achieved and the end result in your output video.

The ramp value for each axis is controlled independently.

Actions:

  1. [Enter] to enter the main menu
  2. [Down] to select Axis x and press [Enter]
  3. [Down] to select Ramp and press [Enter]
  4. [Up] or [Down] to input the number of frames to reach full speed
  5. [Enter] to save or [Right] to abort without saving
  6. [Right] to return to the main menu
  7. [Right] to return to the main screen
  8. [Right] as many times needed to select the desired axis speed
  9. [Up] and [Down] to adjust the desired speed
  10. [Left] to the On/Off control
  11. [Up] to start the program running

Once the program starts running, the speed will set its self to zero for any axis with a ramp value configured.  If you stop the program running before it reaches full speed, it will now see the current speed as the desired speed, and you will have to increase it back to your original value.

Using a Lead-in or Lead-out

A lead-in defines a period of time, in frames from the beginning of the shoot, that the motor should not move.  Conversely, a lead-out defines the period of time from the end of the shoot that the motor should not move.  Each axis can have its own lead-in and lead-out times defined — however, to function, a ramp value must be set for that axis as well.  Leads are executed through the ramping/feathering function of the controller, by simply preventing it from starting a ramp before a certain number of frames have passed (in the case of a lead-in), or reducing the overall number of frames counted before ramping all the way down to zero (in the case of a lead-out).

As with ramping/feathering, a lead-out is only used if the max shots parameter has been set, and therefor the controller can determine when to start reducing speed.

To help clarify this function, we’ll use the same parameters from the ramping example, and add a lead-in and lead-out:

take the following parameter values:

  • Output video = 24 frames per second
  • Max shots = 240 (10 seconds)
  • Ramp rate = 24
  • Lead-in = 24
  • Lead-out = 24
  • Axis speed = 1 inch per minute

The following will happen in the output video:

  • For one second, no movement will occur
  • For one second, the motion will accelerate to full speed
  • For six seconds, the motion will run at full speed (1 IPM)
  • For one second, the motor will decelerate to no speed
  • For one second, no movement will occur

Actions:

  1. [Enter] to enter the main menu
  2. [Down] to select Axis x and press [Enter]
  3. [Down] to select Lead-in or Lead-out and press [Enter]
  4. [Up] or [Down] to input the number of frames to lead in or out with
  5. [Enter] to save or [Right] to abort without saving

The MX2 controller comes pre-calibrated for a load of approximately 1.5kg (~ 3.5 lbs). This is the weight of a medium sized dSLR, zoom lens, and small ball head.

Calibrating is not essential to make use of the MX2 with the Stage Zero Dolly for timelapse use, however it can greatly increase the accuracy of specific distances you dial in when entering values in inches per minute. As the Stage Zero dolly’s motor does not have feedback to the controller, the controller can only tell the motor to move at certain speeds and at certain times. Calibrating the controller allows you to adjust the controller for variations in how the motor behaves under different loads and at different speeds.

Calibration of the motor is saved when the MX2 is powered off, so you only need to re-calibrate when your payload (camera/lens/head/etc.) changes in weight significantly.  If you swap out motors or pulleys, it is important to perform a calibration as well, after adjusting the motor parameters to match your new combination.

Please note that it is impossible for the MX2 to make all speeds accurate at all times.  The calibration routine will allow you to dial-in one or two specific speeds more accurately than others, but as a low-cost system, perfect accuracy is not achievable.

Adjusting the Angle of the Dolly

When operating the dolly at an angle, and using Inches Per Minute (IPM) speed input, you will want to inform the controller of the nearest angle of the track so that it can adjust based on the calibration for that angle.  You may set the angle of the dolly (or any other linear axis) in the Axis Configuration menu for the given axis.   Three angle values are possible: 0, 45, and 90.  The 0degree angle corresponds to the dolly being largely in parallel to the ground, 45 degrees corresponds to the track being at a 45-degree angle to the ground, and 90 degrees to being perpendicular to the ground.  You should pick the angle closest to the one you are at, and when in doubt, err on the side of setting the angle higher.

Actions:

  1. [Enter] to enter the main menu
  2. [Down] to select Axis x and press [Enter]
  3. [Down] to select Angle and press [Enter]
  4. [Up] or [Down] and choose between 0, 45, and 90
  5. [Enter] to save or [Right] to abort

Using Automatic Calibration

Automatic calibration mode adjusts the assumptions the controller makes about the motor’s performance.  By moving at different speeds, in different modes, and in different directions the controller expects the cart to have moved a certain distance.  During automatic calibration, you will measure the distance the cart has moved at each stage, and in doing so the controller will automatically adjust its expectations of the motor’s performance at critical speeds.

You may calibrate the controller for each of the specified angles: 0, 45, and 90 degrees.  Each angle must be calibrated separately, but each time you calibrate, the calibration will be saved and you will not have to repeat it unless your payload substantially changes, or you change out the motor or main drive pulley.

To use automatic calibration, first move the dolly to the middle of the track, either through manual motor control or by loosening the belt and moving it by hand and then make sure that the belt is tightened fully before beginning.   Now, place a ruler flat on the track in a position where neither the angle mounts nor the stabilizer bar will hit it, and line the edge of the ruler up with one of the edges of the cart.  The cart will be moving to the right at first, so let the ruler stick out in that direction.  For 45 degree and higher angles, it is worthwhile to tape down the ruler.

After selecting the angle you want to calibrate for and pressing [Enter], the cart will first move quickly to the right, and ask you to enter how far it went in hundredths of an inch.  (Don’t worry, just getting it close enough in tenths is good enough for most uses.)  Enter the value using the up and down arrow keys and press enter to move to the next step.  The cart will then move to the left and repeat the process, before going into two pulsing mode speed tests.  The entire process should take around 3-4 minutes.

Actions:

  1. [Enter] to enter the main menu
  2. [Down] to select Axis x and press [Enter]
  3. [Down] to select Calibrate and press [Enter]
  4. [Up] or [Down] and choose between 0, 45, and 90 degree calibration modes
  5. [Enter] to start the calibration process, or [Right] to exit without calibrating
  6. After the move is completed, use [Up] and [Down] to input the distance moved in inches
  7. Press [Enter] to save the value you input and repeat five more times
  8. After all calibration steps have been completed, use [Right] to exit the calibration screen

Notes:

  • After a new calibration, you will need to adjust the Calibration Constant Value, which is documented below to finely tune in the calibration
  • If you are using your own motor/gear chain with the MX2, and the calibration does not appear to move at all, adjust the low and high speed targets as indicated below

Adjusting Calibration

The MX2′s calibration routine attempts to determine how much to adjust the on time of the motor based on its performance at default values.  However, most motors behave non-linearly when adjusting their speed by changing the on time.  This means that simply adjusting the on/off time alone is not enough to accurately dial in a speed that was off from the expected target.  Usually, it results in the motor going much slower than expected for low speeds, as the non-linearity of the motor’s behavior increases at the lowest speeds.

To compensate for this, a calibration constant was introduced in the 0.83 version of the MX2 firmware.  This allows you to configure how much of the calibration change is actually applied during run time calculations.  Generally speaking, if the motor still runs too slow after calibration, the constant should be reduced, and if it runs too fast the constant should be increased.

The workflow for finely tuning in a particular speed is as follows:

  1. Set either the low or high speed target to the desired speed (see below)
  2. Run the auto calibration
  3. Set max shots to 60
  4. Set interval to 1, disable all focus and post-exposure delays
  5. Set the desired axis to the desired angle
  6. Set the desired axis to the desired continuous speed on the main screen
  7. Turn the program on, and measure actual distance traveled
  8. Adjust calibration constant
  9. Repeat 7-8 until the speed is tightly dialed-in

Actions:

  1. [Enter] to enter the main menu
  2. [Down] to select Axis x and press [Enter]
  3. [Down] to select Cal. Constant and press [Enter]
  4. [Up] or [Down] and adjust the value as desired
  5. [Enter] to save the value, or [Right] to exit without saving

Setting the Calibration Targets

When you want to dial-in one or two speeds to be your most accurate, you should choose the speeds you use most.  To adjust the speeds used in calibration, you will need to adjust the low and high calibration targets to the speeds you desire.

These values are set in the Main Settings menu.

Actions:

  1. [Enter] to enter the main menu
  2. [Down] to select Settingsand press [Enter]
  3. [Down] to select Cal. Spd. Low or Cal Spd. Hi and press [Enter]
  4. [Up] or [Down] and choose the target speed
  5. [Enter] to save the new value
  6. Repeat calibration process as indicated above

Like most values in the MX2 controller, the Calibration Speed Targets are retained after power-off.

Important Notes:

  • The Low speed target must be lower than the High speed target
  • You must re-calibrate after changing the targets

Adjusting for Very Heavy Weights or Weak Motors

If you’re using the Stage Zero with a large camera/motion control payload, or are using the MX2 with a DIY rig with a smaller motor, you may need to adjust the minimum pulse time to give the motor enough time to get the cart moving at the lowest speeds.   A larger minimum pulse time can make movements at low speeds rougher, so you generally want to keep it as low as possible, while still being able to start moving the cart forward at the lowest speed.

Like most values in the MX2 controller, the Minimum Pulse value is retained after power-off.

Actions:

  1. [Enter] to enter the main menu
  2. [Down] to select Axis x and press [Enter]
  3. [Down] to select Min Pulse and press [Enter]
  4. [Up] and [Down] to adjust the minimum pulse time
  5. [Enter] to save or [Right] to exit without saving

Stop-Motion and Timelapse have slightly a different workflow, namely in that in timelapse you want your exposures to continue uninterrupted, on your set interval, for a period of time.  Whereas, in stop-motion filming, you want to control when each exposure occurs so that you may make set adjustments or take other actions between exposures.  The MX2 supports both of these workflows easily.

Enabling Manual Triggering of Exposure and Motion

In stop-motion, we want to take one exposure and make one move at-will, and have plenty of time to do what we need to do between exposures.  To achieve this, we’ll cause the MX2 to abort its program after a single shot, and we’ll used Fixed Interleave motion control to establish our exact distance moved between shots.  If we set the maximum shot count to 1 for the camera, when the MX2 is told to to turn motion on, it will expose one frame make its required move and stop until it is turned on again.

Actions:

  1. [Enter] to enter the main menu
  2. [Down] to select Cameraand press [Enter]
  3. [Down] to select Max Shots and press [Enter]
  4. [Up] or [Down] and input a value of 1
  5. [Enter] to save or [Right] to abort
  6. [Right] to return to the main menu
  7. [Right] to return to the home screen

You should also be in the Fixed Interleave motion mode before beginning.  On the main screen, input the desired distance to be moved between each shot, and then use [Left] to bring the cursor back to the On/Off value.   Pressing [Up] will cause the MX2 to start running, fire a single shot, move, and then stop running.  To fire the next frame, simply press [Up] again, and so forth.

If need be, you may also fashion a remote switch, connected to port Ext 1,  and use this as a remote trigger to start the next exposure cycle.  For more information see Using Remote Inputs.

 

Most of the motor parameters in the MX2 will never need to be modified if you are using the Stage Zero dolly in the stock configuration.  These parameters are largely designed to adjust distance values listed on the main screen when you input movement in inches per minute.

The MX2 controller displays inches per minute for linear axes by relating the maximum RPM of the motor to the distance traveled by the final drive gear.  If you’re using a pulley or gear as a final output drive (such as for a belt-driven system like the Stage Zero, or a rack-and-pinion driven system), the distance traveled is generally the pitch circumference of the gear.  As these values effect the displayed distances for movements, you should only adjust them when changing something in the drivetrain.  For calibrating different performance under different loads, you shouldcalibrate the axis instead.

Setting Motor RPM

This setting allows you to input the Revolutions Per Minute of the motor you are controlling.  This aids in determining the max speed of the motor.  If you have multiple gear transitions after the motor its self, make sure to account for them in the RPM.  For example, if you have a 2:1 transition from the motor output shaft to your drive gear, you would reduce RPM by one half.

Do not use this setting to adjust performance of the motor under load!  Calibrate the axisinstead.

Like most settings, the value is stored when powering off, and only needs to be changed when you change motors.

Actions:

  1. [Enter] to enter the main menu
  2. [Down] to select Axis x and press [Enter]
  3. [Down] to select RPM and press [Enter]
  4. [Up] or [Down] to input the correct RPM for your motor
  5. [Enter] to save or [Right] to abort without saving

Setting Output Drive Distance

To allow you to enter speeds and distances in actual distance, versus percentages, the MX2 must be aware of the actual distance moved per revolution of the motor.  For most linear axes, the actual distance traveled will be based on the pitch circumference of the final output gear — for example: the pitch circumference of a drive pulley or the pitch circumference of a pinion on a rack-and-pinion drive.

Like most settings, the value is stored when powering off, and only needs to be changed when you change motors.

Actions:

  1. [Enter] to enter the main menu
  2. [Down] to select Axis x and press [Enter]
  3. [Down] to select Dist. per Rev. and press [Enter]
  4. [Up] or [Down] to input the correct pitch circumference (in inches) for your output gear
  5. [Enter] to save or [Right] to abort without saving

Sometimes it happens to the best of us: we get a little carried away and then we have no idea what setting we messed up, or how, and we just want to get everything back to where we started.  The MX2 saves most of the values you enter into permanent memory, reducing the amount of data entry you have to do for subsequent shoots, and letting you store calibration and so forth.  There is a factory reset option which resets this permanent memory to its default state so that you can wipe all changes clean.

Resetting the permanent memory requires a restart of the MX2 controller, and it may take longer than normal to restart the first time after resetting the memory.

You should always reset the permanent memory after doing any firmware upgrade.  Retaining memory after an upgrade can result in some values that cannot be modified.

Resetting Stored Memory to Defaults

To reset the permanent memory on the MX2, you will need to first enable the factory resetparameter, and then restart the MX2.

Actions:

  1. [Enter] to enter the main menu
  2. [Down] to select Settingsand press [Enter]
  3. [Down] to select Reset Mem and press [Enter]
  4. [Up] or [Down] and choose  on
  5. [Enter] to save the value
  6. Power-cycle the MX2 (may start slower than normal the first time after a memory reset)
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