Stevens R. Miller
Well-Known Member
Those of you who have flattered me for my ASCII artistic skills in the past may have to be more forgiving than admiring this time. If the diagrams below are incomprehensible, I'll create some actual images and link to them.
I am working with a Scene Setter-48, very kindly lent to me by JimOC_1. It's an impressive gizmo that meets my basic need for a one-on-one box with 48 faders that can control 48 dimmers. In its A/B preset mode, it allows the operator to cross-fade from 24 preset faders to another 24 preset faders. But, in that mode, it only controls 24 dimmers total, not 48.
One can record a "scene" into a a fader. A scene can be (among other things) any preset level for each of the full 48 dimmers. So, if one cue calls for lights L1, L2, and L3 to be full, one sets faders 1, 2, and 3 to full, and then records that setting into a submaster (the faders do double-duty here: in the recording mode, they set dimmer levels, and you assign a complete preset to a fader with its bump button; in the playback mode, the faders become submasters and raise/lower the complete preset recorded into them).
If the next cue calls for lights L3, L4, and L5 to be at 50%, one sets faders 3, 4, and 5 to 50%, and then records that setting into a submaster.
This works pretty well, allowing the cues to be played back during a show by simply raising and lowering the submaster that has the cue you need. The Scene Setter-48 can store 96 cues this way (in four pages of 24 each), which is plenty for our needs. It would be a rare show indeed, for us, that needed more that 96 distinct cues. By reusing them (cues 12, 17, 85, and 102 might all be for, say, scenes in a basement, with the lighting always the same in each scene, so submaster 7 might be used to store that scene, and be played back four times during the show).
My problem arises from the difference between cross-fades and transitioning from one submaster to another, where the level for a given dimmer during transition is governed by the highest-takes-precedence (HTP) rule. A cross-fade sets intensity by a parametric equation that sums weighted values of the incoming and outgoing levels for a given dimmer. So, if L1 is at 80% for Cue A (I'll use letters here for cues, to keep them distinct from the numbers I use for lights), and L1 is also at 80% for Cue B, for t=0 to t=1, where t is the parameter that linearly varies from 0 to 1 during the cross-fade, the intensity of L1 is set by this equation:
This expands to:
Which reduces to:
Hardly surprising. L1's level is 80% throughout the cross-fade, which is what we want.
But, if one sets L1 to 80% and records that into submaster 1, sets it again to 80% and records that into submaster 2, raises submaster 1 to full, then simultaneously runs submaster 1 to zero while running submaster 2 to full, L1 does not stay at a constant 80%. Rather, at t=.5, when both submasters are at 50%, L1 is at 40%. Owing to HTP, for t from 0 to .5, L1 drops linearly from 80% to 40%, and from .5 to 1, L1 increases linearly from 40% to 80%.
One could "solve" this problem by first running submaster 2 to full, then running submaster 1 to zero, but that "fix" only works in the case where the level for a light doesn't change. It isn't a general fix. Here are some (dubious) ASCII graphs that show how a couple of two-light cues make their transitions for each option: cross-fade, simultaneous fade on two submasters, and fading full up on the incoming submaster, then full down on the outgoing submaster:
I don't know that there's any true, general-case way around this issue, but folks here constantly surprise me with their accumulated wisdom, so I'll hope for the best.
How can I simulate a cross-fade when I only have submasters to use?
I am working with a Scene Setter-48, very kindly lent to me by JimOC_1. It's an impressive gizmo that meets my basic need for a one-on-one box with 48 faders that can control 48 dimmers. In its A/B preset mode, it allows the operator to cross-fade from 24 preset faders to another 24 preset faders. But, in that mode, it only controls 24 dimmers total, not 48.
One can record a "scene" into a a fader. A scene can be (among other things) any preset level for each of the full 48 dimmers. So, if one cue calls for lights L1, L2, and L3 to be full, one sets faders 1, 2, and 3 to full, and then records that setting into a submaster (the faders do double-duty here: in the recording mode, they set dimmer levels, and you assign a complete preset to a fader with its bump button; in the playback mode, the faders become submasters and raise/lower the complete preset recorded into them).
If the next cue calls for lights L3, L4, and L5 to be at 50%, one sets faders 3, 4, and 5 to 50%, and then records that setting into a submaster.
This works pretty well, allowing the cues to be played back during a show by simply raising and lowering the submaster that has the cue you need. The Scene Setter-48 can store 96 cues this way (in four pages of 24 each), which is plenty for our needs. It would be a rare show indeed, for us, that needed more that 96 distinct cues. By reusing them (cues 12, 17, 85, and 102 might all be for, say, scenes in a basement, with the lighting always the same in each scene, so submaster 7 might be used to store that scene, and be played back four times during the show).
My problem arises from the difference between cross-fades and transitioning from one submaster to another, where the level for a given dimmer during transition is governed by the highest-takes-precedence (HTP) rule. A cross-fade sets intensity by a parametric equation that sums weighted values of the incoming and outgoing levels for a given dimmer. So, if L1 is at 80% for Cue A (I'll use letters here for cues, to keep them distinct from the numbers I use for lights), and L1 is also at 80% for Cue B, for t=0 to t=1, where t is the parameter that linearly varies from 0 to 1 during the cross-fade, the intensity of L1 is set by this equation:
Code:
L1 = (1 - t) x .8 + t x .8This expands to:
Code:
L1 = .8 - .8t + .8tWhich reduces to:
Code:
L1 = .8Hardly surprising. L1's level is 80% throughout the cross-fade, which is what we want.
But, if one sets L1 to 80% and records that into submaster 1, sets it again to 80% and records that into submaster 2, raises submaster 1 to full, then simultaneously runs submaster 1 to zero while running submaster 2 to full, L1 does not stay at a constant 80%. Rather, at t=.5, when both submasters are at 50%, L1 is at 40%. Owing to HTP, for t from 0 to .5, L1 drops linearly from 80% to 40%, and from .5 to 1, L1 increases linearly from 40% to 80%.
One could "solve" this problem by first running submaster 2 to full, then running submaster 1 to zero, but that "fix" only works in the case where the level for a light doesn't change. It isn't a general fix. Here are some (dubious) ASCII graphs that show how a couple of two-light cues make their transitions for each option: cross-fade, simultaneous fade on two submasters, and fading full up on the incoming submaster, then full down on the outgoing submaster:
Code:
Cue A: L1 @ Full
L2 @ Full
Cue B: L1 @ Full
L2 @ 0
Cross-fade:
L1A & L2A|----------L1B
| \
| \
| \
| \
| \
| \
| \
| \
| \L2B
+---------->
Simul-fade:
L1A & L2A|\ /L1B
| \ /
| \ /
| \ /
| \/
| \
| \
| \
| \
| \L2B
+---------->
Fade up/down:
L1A & L2A|----------L1B
| |
| \
| |
| \
| |
| \
| |
| \L2B
+---------->
Cue A: L1 @ 50%
L2 @ 50%
Cue B: L1 @ Full
L2 @ 0
Cross-fade:
| _/L1B
| _/
| _/
| _/
L1A & L2A|_/
|\_
| \_
| \_
| \_
| \_L2B
+---------->
Simul-fade:
| /L1B
| /
| /
| /
L1A & L2A|\_ /
| \_/
| \_
| \_
| \_L2B
+---------->
Fade up/down:
| _____L1B
| /
| /
| /
| /
L1A & L2A|------
| \
| \
| \
| \L2B
+---------->I don't know that there's any true, general-case way around this issue, but folks here constantly surprise me with their accumulated wisdom, so I'll hope for the best.
How can I simulate a cross-fade when I only have submasters to use?
