2.5 HTP and LTP

Taditional theater desks that are not designed to handle moving lights will work on a Highest Takes Precedence (HTP) basis. This means that if a fixture's intensity is being controlled by two different parts of the console, such as a playback and a submaster, the intensity will be at the highest of the two levels. For example, if in the playback fixture 1 is at 50%, and in the submaster it is at 100%, then the level seen on stage will be 100%. If the submaster is reduced to 40%, then the on-stage level will be 50%, because the level in the playback is higher and will take precedence.

This system generally works well for non-moving light consoles, but moving lights introduce a problem. Parameters other than intensity don't have ‘higher’ and ‘lower’ values: a colour of red is not higher or lower than green, and a pan of 50% is not higher or lower than one of 20%. Working with moving lights needs a new way to decide the precedence, called Latest Takes Precedence (LTP).

With this system, the fixture parameters are at the value they have been most recently assigned. In our example, moving the submaster to 40% would result in a level of 40%, because this is the latest instruction and will take precedence. The submaster would effectively ‘grab’ control of the parameter from the playback. Of course, running another cue in the playback might grab it back again.

Many moving light consoles use HTP for intensity and LTP for all other parameters. By default, Hog 4OS uses LTP for all parameters, but you can assign individual cuelists to use HTP for intensities (all other parameters are still LTP); see Using HTP and LTP.