SPDINTERP(OPCSDEFS) Optical Printer Control System SPDINTERP(OPCSDEFS)
NAME
spdinterp - configure exposure speed interpolations
SYNOPSIS
spdinterp [slavechan] [masterchan] [lowpos] [highpos] [total] [samples]
EXAMPLES
spdinterp c e -1000 1000 2 0.5 1.5
- - ---------- - -------
| | | | |
| | | | The exposure compansation values.
| | | |
| | | # of exposure compenation values.
| | |
| | The extreme positions for the 'e' (zoom) channel.
| |
| 'e' (zoom) is the master channel.
|
'c' (camera) exposure speed slaved to [masterchan]
DESCRIPTION
SPDINTERP allows a channel's normal running speed to be affected
by the position of some other channel. Slewing speeds are NOT affected.
[slavechan] is the channel whose exposure speed will be affected.
This is usually always the 'c' (camera) channel.
[masterchan] is channel whose position will dictate the
exposure speed of the [slavechan]. Normally, this is the zoom channel,
so that moving the zoom will auto-compensate the exposure.
[lowpos] [highpos] are the low and high positions
the [masterchan]; the extreme positions which define the
range over which the interpolation will take place.
[total] The total number of exposure compensation sample
values. NOTE: If [total] is '0', this will cancel any previous
SPDINTERP(OPCSDEFS) specifications for the [slavechan] channel.
[samples] are the compensation values, which will
be multiplied to [chan]'s current exposure speed, to create
the actual, 'compensated' exposure speed.
A value of 2.0 will effectively double the exposure speed,
0.5 will cut the exposure speed by half, 1.0 will leave the
exposure unmodified, etc.
Each sample position should be separated by white space (tabs,
spaces, CRLFs) and there should be as many samples as specified
by [total].
OVERVIEW
When an SPDINTERP is set up on a slave channel, it is like defining
a look up table through which positions on the master channel affects
the exposure speed of the slave channel.
♀
Requests that fall between values in the lookup table are computed
as a linear interpolation between the two neighboring lookup values.
The resulting interpolation results in a 'compensator value' that
is simply multiplied to the current camera speed, to get the
compensated 'actual speed'.
HOW SPDINTERP WORKS
===============================================================
= spdinterp c e -1000 1000 3 .5 1.0 2.0 =
= | | | | | =
= | | | | Last sample position =
= | | | First sample position =
= | | Total samples =
= | High =
= Low =
===============================================================
Figure A.
======================================================================
= Zoom Clip Interped Compensated =
= Posns Window Samples Compensator Actual Speed =
= Values (SPD=0.5) =
= | =
= -2000 ----> | ----- 0.50 ----> 0.25 =
= -1500 ----> | LOW = -1000 /------ 0.50 ----> 0.25 =
= -1000 ----------------------> 0.5 -------- 0.50 ----> 0.25 =
= -500 ----------------------> -------- 0.75 ----> 0.38 =
= 0 ----------------------> 1.0 -------- 1.00 ----> 0.50 =
= 500 ----------------------> -------- 1.50 ----> 0.75 =
= 1000 ----------------------> 2.0 -------- 2.00 ----> 1.00 =
= 1500 ----> | HIGH = 1000 \------ 2.00 ----> 1.00 =
= 2000 ----> | ----- 2.00 ----> 1.00 =
= | =
======================================================================
Figure B.
Whenever the zoom moves to a new position, it is clipped through the
'clipping window' between the [low] and [high]. This creates a lookup
into the sample list using a linear interpolation. Results in an
'Interped Compensator Value', which is then multiplied by the current
speed of the camera (SPD=0.5), resulting in 'Compensated Actual Speed'.
Note when zoom is 0 (exactly between the LO and HIGH values) the actual
speed is the same as the camera speed; the compensator value becomes
1.0, which multiplied against the camera speed yields no change. This
is because the 'zero' position on the zoom is usually 1:1, which is
where exposure speeds should match the actual speed.
For this reason, it is best if the extreme zoom positions are totally
opposite (2:1 vs 1:2, or 10:1 vs 1:10, etc), and the 'middle value'
in the samples is 1.0. This way if zoom is 1:1, exposure is unchanged.
SEE ALSO
FEED(OPCS) - feed new positions to motors every camera frame
INTERP(OPCSDEFS) - set up interpolation points
ORIGIN
Version K1.12e+ Gregory Ercolano, Venice California 04/12/98