FDI(OPCS), FDO(OPCS)    Optical Printer Control System     FDI(OPCS), FDO(OPCS)

    NAME
        fdi/fdo  - set up an automated fade in/out

    USAGE
        fdi [-x] frames    # set up a 'fade in'
	fdo [-x] frames    # set up a 'fade out'

	The -x option overrides the error message that warns you about doing a
	fade when the shutter isn't fully open/closed. This allows you to
	do fades from any fader position.

    EXAMPLES
        fdi 24             # Set up a 24 frame fade in
        fdi -x 24          # 24x fade, regardless of current fader position

    DESCRIPTION
        Sets up a fade. Once set, whenever the camera is told to expose frames
	(with CAM(OPCS), REP(OPCS), etc), the fader will automatically move 
	to the proper position before exposing each frame.

	Fades are based on a logarithmic curve that can be customized 
	with FLOG(OPCSDEFS).

	Fades can operate on either still or moving images, depending on the
	command used for exposing film;

	    1) fdi 12 cam 12          # fade in on held image
	    2) rat 1 1 fdi 12 rep 12  # fade in on moving image
	    3) rat 1 2 fdi 12 rep 6   # fade in with step print

	#1 sets up and shoots a 12 frame fade-in on a still projector image.
	#2 sets up and shoots a 12 frame fade-in on a moving projector image.
	#3 sets up and shoots a 12 frame fade-out on a moving projector image
	on twos (step print).

	Fades remain in effect until all frames of the fade have been shot.
	A fade can be cancelled midway using any one of these commands:

	    opn, cls, shu, fdi 0, fdo 0.

	The following effectively shoots the exact same thing:

	    > fdi 12 cam 12
	    > fdi 12 cam 6 cam 6

     NOTES
	> fdi 0, fdo 0 or a SHU(OPCS) command with any value
	  will cancel any pending fade or dissolve.

	> A status message near the fader's counter shows how many frames are 
	  left to go for the fade.

	> Normally, the fader must be:

	    o OPEN before executing FDO
	    o CLOSED before executing FDI

	  ..otherwise an error is shown. The only exception is if the
	  -x flag is supplied, preventing these warnings, shooting the
	  new fade based on the fader's *current* position.

	Below are some common errors:

	    fdi 12  cam 11 fdo 12  cam 12
	                   ^bombs here: only 11x into a 12x FDI.

	    opn  fdi 12  cam 12
	         ^bombs here: fader is already open

	It's hard to see such errors in large '.run' scripts, so it's 
	advised to test scripts with 'motors off' to find such problems 
	quickly, without wasting film or waiting for motors to move.

    SEE ALSO
        OPCS Commands
        CAM(OPCS)            - shoot camera (fades/dissolves too)
        OPN(OPCS), CLS(OPCS) - open/close fader shutter
        SHU(OPCS)            - move fader to an absolute position in degrees
        DXI(OPCS), DXO(OPCS) - set up dissolve in/out
        FDI(OPCS), FDO(OPCS) - set up fade in/out

        OPCSDEFS Commands
        FLOG(OPCSDEFS)   - set Fader LOGarithmic curve for custom fades
        FRANGE(OPCSDEFS) - set fade/dx's degrees range (for Hicon film stocks)
        INTERP(OPCSDEFS) - set interpolation positions (fader, focus, etc)
        SLOP(OPCSDEFS)   - correct for slop in a motor (fader, focus, etc)

        General
        MATH(DOCS)       - math expressions (for use in frame specifications)
        SYNTAX(DOCS)     - online calculator and OPCS math expression syntax

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