I found a good article to read regarding HTP/LTP as it pertains to Lighting Fixtures. Good read and it explains quite a bit.
http://www.onstagelighting.co.uk/learn- ... -basics-5/
HTP/LTP Information
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Jon
Hi Tavon, this is a really cool article which explains a lot about HTP vs LTP for people who are just starting to understand. It does overlook the fact (and sort of suggests that this is irrelevant when in fact it isn't) that LTP can be just as important for intensity-only channels (i.e., dimmers) and has been used in theatrical lighting for years before moving lights became prevalent.
In fact, prior to electronic dimming (back in MY day LOL when we dimmed lights with huge handles directly attached to rheostat-type controls - ugh!) because in those days, the last thing you did to a light was what happened to it, i.e., LTP. Then came SCR-controlled dimming in the 70s and early 80s and the old-style transformer dimming slowly disappeared. Electronic dimming made HTP possible, in fact it was pretty much standard (improved with the advent of dipless fades so that if you faded a channel from 100% in one cue to 100% in another, the light never went down to 50% as the two sliders met in the middle at 50%, instead it would always fade from the previous level directly to the level in the next cue, i.e., dipless).
But LTP can still be useful in straight dimming, especially if you have complex cues. Consider this except from the ETC Express board manual:
### LTP Channels
Channels may also be defined in the console to follow the Latest Takes
Precedence (LTP) rule. An LTP channel obeys the latest command to set
its level. When the command is to fade to a level, an LTP channel can fade
either in a physical fader (in the foreground) or in a background fader. Each
LTP channel has its own background fader.
An LTP channel fades in the foreground if its level moves to a new level
in the next cue. When a channel is fading in the foreground and no change
in that channel is commanded by the next cue, the fade continues in the
background. A cue stops running in the background when the last of its
channels stops fading in the background. Up to 600 cues may run in the
background at once.
For example, consider three cues recorded for channels Chan 1, Chan 2
and Chan 3, all of which are set as LTP channels. The cues contain
percentage levels for these three channels as follows:
Chan 1 Chan 2 Chan 3
Cue 1 25 0 0
Cue 2 25 50 0
Cue 3 50 50 50
When Cue 1 starts, channel Chan 1 starts fading to level 25 with Cue
1 timing.
If Cue 2 starts before Cue 1 ends, channel Chan 1 continues fading in
the background with Cue 1 timing and channel Chan 2 starts fading in
the foreground to level 50 with Cue 2 timing.
If Cue 3 starts before Cue 2 ends, channels Chan 1 and Chan 3 start
fading in the foreground to level 50 with Cue 3 timing; channel Chan
2 continues fading in the background with Cue 2 timing.
In fact, prior to electronic dimming (back in MY day LOL when we dimmed lights with huge handles directly attached to rheostat-type controls - ugh!) because in those days, the last thing you did to a light was what happened to it, i.e., LTP. Then came SCR-controlled dimming in the 70s and early 80s and the old-style transformer dimming slowly disappeared. Electronic dimming made HTP possible, in fact it was pretty much standard (improved with the advent of dipless fades so that if you faded a channel from 100% in one cue to 100% in another, the light never went down to 50% as the two sliders met in the middle at 50%, instead it would always fade from the previous level directly to the level in the next cue, i.e., dipless).
But LTP can still be useful in straight dimming, especially if you have complex cues. Consider this except from the ETC Express board manual:
### LTP Channels
Channels may also be defined in the console to follow the Latest Takes
Precedence (LTP) rule. An LTP channel obeys the latest command to set
its level. When the command is to fade to a level, an LTP channel can fade
either in a physical fader (in the foreground) or in a background fader. Each
LTP channel has its own background fader.
An LTP channel fades in the foreground if its level moves to a new level
in the next cue. When a channel is fading in the foreground and no change
in that channel is commanded by the next cue, the fade continues in the
background. A cue stops running in the background when the last of its
channels stops fading in the background. Up to 600 cues may run in the
background at once.
For example, consider three cues recorded for channels Chan 1, Chan 2
and Chan 3, all of which are set as LTP channels. The cues contain
percentage levels for these three channels as follows:
Chan 1 Chan 2 Chan 3
Cue 1 25 0 0
Cue 2 25 50 0
Cue 3 50 50 50
When Cue 1 starts, channel Chan 1 starts fading to level 25 with Cue
1 timing.
If Cue 2 starts before Cue 1 ends, channel Chan 1 continues fading in
the background with Cue 1 timing and channel Chan 2 starts fading in
the foreground to level 50 with Cue 2 timing.
If Cue 3 starts before Cue 2 ends, channels Chan 1 and Chan 3 start
fading in the foreground to level 50 with Cue 3 timing; channel Chan
2 continues fading in the background with Cue 2 timing.