Map tone to the redscale palette
Redscale is a loading trick, not a filter. The film is respooled so the emulsion faces away from the lens and light reaches the red-sensitive layer first, through the orange base. The other two layers get whatever survives. Shadows come out deep red, midtones orange, highlights yellow.
Each pixel’s tone drives three separate curves here, one per channel, rather than a single hue rotation. Red rises early with a gamma near 0.42, green rises later, and blue stays near zero until the brightest values.
Redscale amount
The blend between the original pixel and the mapped one. At 100% the source colour is gone completely, which is what real redscale looks like. Values around 70% leave a trace of the original hue and read as a warm cross-process instead.
Nothing else in the panel matters at 0%.
Yellow highlights
Where the green record enters. Low values hold green back until near-white, so the frame stays red and orange with almost no yellow. High values bring green in through the midtones, producing the yellow-into-amber highlights typical of an overexposed redscale roll.
This is the single control that decides whether a shot reads as “red photo” or “redscale”.
Exposure and contrast
Exposure runs before the channel curves, so it changes which parts of the image land in the red band versus the yellow band, not just overall brightness. Pushing exposure up moves more of the frame into yellow; pulling it down drives everything toward red.
Contrast pivots around 0.46 rather than mid-grey. Redscale negatives are dense and typically need contrast added back in scanning, which is why the default sits positive.
Example: building against sky
Try 88% amount, 55% yellow, 18% blue retention, -18% exposure, 22% contrast. The sky should land yellow-orange and the shaded wall deep red. If the whole frame is one flat orange, raise contrast or drop exposure so the tones spread across the curves. If shadows go pure black, raise blue retention to around 30%.