SPD(OPCSDEFS)		Optical Printer Control System		SPD(OPCSDEFS)

    NAME
        spd - configure the default and fastwind/slewing speeds for a motor

    SYNOPSIS
        spd [chan] [normal] [fast] [scale] [offset]

	NOTE: any of the arguments [normal] [fast] [scale] [offset] can
	      be a dash (-), indicating that argument won't be modified.

    EXAMPLES
        spd c .25 .1 1.0 0.0  # sets default speed for the camera motor:
                              #  .25 is normal running speed,
                              #  .10 is the slew speed (used by SEEK)
                              #  1.0 and 0.0 indicate speeds are specified
                              #      as ROTATIONAL speeds.

        spd c .25 .1 3.0 0.0  # Same as above, but shows correct [scale]
                              #  value so EXPOSURES can be specified
                              #  for a 120 deg. shutter (3.0 = 360/120).

        spd c .25 .1 2.1176   # Same as above, but shows correct [scale]
                              #  value so EXPOSURES can be specified
                              #  for a 170 deg. shutter (2.1176 = 360/170)

    DESCRIPTION
        Normally, one of these commands for EACH motor should appear in
        the OPCSDEFS.OPC file. This command sets the initial running speeds
        for a motor, as well as how speeds are specified (i.e., rotational
        or exposure speeds. See below.)

        This command also allows SCALEs and OFFSETs to be applied to speed
        values automatically to let you specify EXPOSURE speeds instead of
        rotational speeds...

    ROTATIONAL SPEED
        An example of a rotational speed could be .25, which would mean: a
        full rotation of the camera shaft will occur in .25 of a second, or
        1/4 a second. This is how motor speeds are normally handled by the 
        software.

    EXPOSURE SPEED
        An example of an exposure speed of .5 would mean the film exposes
	to light for 1/2 second. Since most shutters are 170 degrees 
	(ie. exposing light for 170 degrees out of the total 360 degrees 
	of rotation), the [scale] value can be used to compensate. You will
	want to decrease the camera's rotational speed. To do this, multiply
	360/170 times the current speed to compensate for the fact that the
	shutter is only open for a fraction of a rotation.

        This is where the [scale] argument comes in. By setting [scale] to
	2.1176 (360/170), you can then specify speeds as 'exposure speeds',
	and the system will compensate automatically. If you have a 120 
	degree shutter, use 3.0 (360/120) for the [scale] value.

        You need only do this for the camera motor..the projectors do not
        have to be set up this way, since the projectors always slave to
        the camera's speed whenever a tandem run is executed.

    EQUATION
        The following equation shows how scales and offsets are first applied
        to motor speeds:

               actual motor speed = (norm_speed * scale) + offset * spdinterp

        A value of 1.0 for [scale], and 0.0 for [offset] makes NO CHANGE 
	in the norm_speed (normal running speed), and thus will reflect shaft 
	rotation speed.

	'spdinterp' will affect the equation only if a SPDINTERP(OPCSDEFS)
	command is configured, in which case the speed will be modified 
	according to the current position of the SPDINTERP's master channel.

    SEE ALSO
        MRP(OPCSDEFS)     - set 'maximum ramping pulses' for shutter runs
        RAMP(OPCSDEFS)    - set maximum accelerations and velocities
        SPD(OPCS)         - set the camera's exposure speed
        SPD(OPCSDEFS)     - set a motor's running speeds
	SPDINTERP(OPCSDEFS) - set auto-interpolation for exposure speeds

    BUGS
	Speeds of 0.0 will cause the software to blow out unpleasently.
	Avoid setting a motor's speed to zero, or doing any operation
	that would result in an actual speed of zero.

    ORIGIN
	Gregory Ercolano, Los Feliz California 11/29/89