CTO Gel

What this is about

CTO is the direction of travel most crews need most often, because a location interior usually has tungsten or warm LED practicals already burning and the daylight coming through the glass has to join them. Full CTO takes a nominal 5600 K source down to roughly 3200 K, and the graded versions — quarter, half, three-quarter — let a gaffer land anywhere between. The biggest application is not a lamp at all but a window: rolls of CTO taped or magnetically fixed to the pane warm an exterior that would otherwise sit blue against every practical in the room.

A term only helps when everyone on set means the same thing by it — so what follows is how it is used, not a dictionary definition.

What runs differently here

In planning terms, that means:

• Full CTO shifts a daylight source down toward tungsten balance; quarter and half grades cover the ground in between.
• It costs roughly a stop at full strength, which is factored in when the HMI size for a scene is chosen.
• On windows it usually arrives as wide rolls, and the rigging hours for taping large panes belong in the schedule.

With TillyGen

When TillyGen's location notes record a daylight window in a tungsten interior, the CTO rolls and their rigging time are in the plan beforehand.

Change one constraint and the consequences travel through the whole plan: affected shots are flagged, the call sheet is regenerated, and nobody keeps working from yesterday's version.