When the two reads point opposite ways

The problem is mixed this time. The plate sits under key, but somebody has already over-stretched it. So the two reads point opposite ways: the key level has to go up while the ratio comes back.

```sketch { "kind": "trace", "shape": "crushed", "ghost": true, "regions": [ { "band": "body", "label": "level up" }, { "band": "floor", "label": "ratio back", "accent": true } ], "caption": "The target bands ask for two different corrections." } ```

A senior colorist runs a mixed plate in three steps, in this order, every time. Read floor, ceiling and body. Make the two moves. Then read the traces again before you submit, because the last two points hide in the fine moves. This ghost is a graded master's as well, so undoing the fault leaves you somewhere the read has to correct.

What the ghost cannot tell you

Before you pass it, be exact about the instrument. This ghost uses a luma waveform, which shows a weighted combination of red, green, and blue signal values. Other waveform modes can display RGB channels, but this exercise intentionally withholds them.

So a floor, a ceiling and a distribution survive the picture going away, and a cast does not. Two shots with identical traces can be a mile apart in color, and no move you can make on this bench would tell you. Neither can the ghost say:

which of the three channels is riding high
whether the highlights lean one way while the shadows lean the other
how far the frame's color reaches from center
whether a face is sitting on its line

Those are parade and vectorscope reads, and they need the picture or the color scopes back.

That is not a flaw in the exercise. It is the exercise: this room trains the half of a match you can still do with the picture gone, and the next rooms hand the other half back.

Pass it and you have proven that the numbers are enough on their own, for the part of the job the numbers cover. The next room grades you against a different reference, the one the audience already has in its head. It asks for judgment rather than a fix. The first session there clears a drift out of a frame. The last one puts a drift in on purpose, and it has to stop before that reads as a mistake.