Everything you need to know about Tone Curve
Tone Curve applies adjustable S-curve transformations to your image, providing smooth, film-like contrast control. Adjust the curve strength for classic contrast enhancement and midtone bias to shift overall brightness – all in a simplified two-parameter interface.
Parameters
- Curve Strength
Controls the intensity and direction of the S-curve (-1 to +1). Positive values create a classic S-curve that darkens shadows and brightens highlights, increasing contrast with a natural, film-like quality. Negative values create an inverse curve that lifts shadows and compresses highlights, reducing contrast for a flat, matte look. - Midtone Bias
Shifts the overall brightness of midtones (-1 to +1). Positive values brighten the image (like increasing gamma), making midtones lighter while anchoring blacks and whites. Negative values darken midtones for a moodier, low-key look. - Mix
Blends the curve-adjusted result with the original image. At 0, no change is visible. At 1.0, the full tone curve adjustment is applied.
How It Works
The filter applies a mathematically smooth curve to each RGB channel. The curve strength parameter shapes the curve into an S (positive) or inverse-S (negative), while the midtone bias applies a power function that shifts the middle tones without affecting the endpoints.
Curve Strength Effects
- -1.0 to -0.5 – Reduced contrast, lifted shadows, matte/faded look
- -0.3 to 0 – Subtle contrast reduction, softer image
- 0 – No curve applied (linear)
- 0 to +0.3 – Subtle contrast boost, adds punch
- +0.5 to +1.0 – Strong S-curve, dramatic contrast, deep blacks and bright highlights
Tips
- Curve strength +0.2 to +0.4 gives classic film-like contrast enhancement
- Negative curve strength + positive midtone bias = faded vintage look
- Use midtone bias to fine-tune exposure without clipping highlights or shadows
- For more precise control with individual points, use the Curves filter