I just don't get it!
What seems to be the problem?
Bobblehead Fred, I just don't understand any of this. LTP, HTP, tracking, preset, move-fade, state?
What does it all mean?
I see. Well, maybe a little history of intensity control could help shed some light.
The concepts HTP, LTP, tracking, preset, move-fade, and state are not new ideas.
They've actually been around in theater lighting for a very long time and are still used in our modern
lighting consoles. But let's take a look at how these concepts got their start.
First, we'll examine LTP, tracking, and move-fade using this set of resistance dimmers.
Long before modern computerized lighting consoles, resistance dimmers were common for controlling lights.
Each dimmer has a handle attached to it, so when you move the handle, you can
directly fade that dimmer up and down.
When you let go of the handle, the dimmer will stay at that level until you move the
lever again. That's latest take's precedence, or LTP. The last action remains until another action happens.
So let's create a look with our three dimmers, and we'll call this scene one.
Dimmer one is at 50 percent. Dimmer two is at 50 percent. And dimmer three is at 0.
For scene two, I'd like dimmers two and three to go to full. Since we didn't move dimmer
one's lever, it stayed at 50 percent. Since the last action of dimmer one didn't change,
that information 'tracked' from scene one into scene two. To run lights this way, I only
need to mark down which levers moved, and when. This method of recording only the moves
and allowing unchanging levels to remain on gives us the term 'tracking'.
When I execute a cue, each lever that gets moved can fade in its own time, so while one
lever is being moved slowly, other levers can be moved quickly without affecting the
slower fade in progress. This gives us the term 'move-fade'.
Okay. I think that makes sense. But where do HTP, preset, and state come from, then?
I'm glad you asked. So resistance dimmers were fine for a while until theaters started
using more and more lights and needing more and more dimmers to control them.
The average stagehand has two arms and at least one leg. So that seriously limits how many levers they
can control at one time. Plus, resistance dimmers are rather large and bulky and were
often installed backstage where they took up lots of valuable space. So the preset board was born.
Early preset boards are made up of several banks of faders. Each fader in a bank is used
to control a dimmer, just like a lever of the resistance dimmer. Each bank of faders
controls the same dimmers, which allow you to preset multiple looks. Master faders are
used to control the banks and fade between them. If the master faders for two or more
banks are active or above zero, then the faders that have the dimmers at the highest value
have control. This is called 'highest takes precedence' or 'HTP'. If we lower the fader
that had control, the next highest fader would then take control.
Unlike the resistance dimmers, where unchanging levels track forward, the preset board requires
the user to create the entire lighting look on each bank of faders. Let's use the same
example as earlier. That's my first scene. For the second scene, I want dimmers two and
three to go to full, and dimmer one to remain at 50. If I don't write down that fader one
is at 50 in scene two, then when I fade from scene one to scene two, dimmer one goes to
0 percent and stays off - so I have to set fader one to 50 percent in the second bank, too.
That's called 'preset', because in order to preset you cues accurately in each
bank of faders, you need to write down every fader's level. Unlike move-fade, where only
moves are executed, with preset boards, the entire look or state is replaced as you fade
from scene to scene. Due to that, a slow moving level may be overtaken by a faster incoming cue.
Okay, let's see if I understand this.
LTP, or latest takes precedence, means a dimmer will output the last level it was given.
And HTP, or highest takes precedence, means the dimmer will output the highest level it's
being given if there are many active scenes. Okay, in a tracking system, you only write
down or record the moving levels. And static levels stay put until you move them to a new level.
And in a preset system, you have to write down all the levels in each cue so that
the banks of faders can be set up accurately. Then, because a tracking system only executes
the moving levels, you get move-fade behavior where each moving level can fade in its own
time, easily, even when cues are overlapping.
In a preset system, the entire lighting state is replaced with a whole new state each time
you crossfade from scene to scene, meaning special handling is needed if you want to
let a long fade run on its own while other cues are executed, right?
Exactly. And remember, those concepts are all still used today in computerized lighting
consoles, so the resistance dimmer laid the groundwork for our modern tracking consoles
like Eos, Ion, and Obsession, while the preset board led us to the Express, Expression, and
Congo consoles. The computerized lighting consoles make it possible to solve the editing
and playback challenges of the old manual systems, but these core ideas will usually
surface at some point as you're building your show.
Gee, thanks, Bobblehead Fred. That's a lot clearer now.
But how do I know which console is right for me?
That's an excellent question. Ooh, unfortunately, we're out of time.
We'll have to save that for another day.