The built-in editor uses linear light mathematics for accurate colour processing. Here's what each slider actually does and how to use them together.
The PhotoRoads editor processes images in linear light — the same approach used by Lightroom and Capture One. This matters because most web-based editors manipulate gamma-encoded pixels directly, which produces colour shifts and inaccurate tonal changes. Our editor converts to linear light first, processes there, and re-encodes back to sRGB on output.
Here's what each control actually does.
Applies a 2^(EV/100) multiplier in linear light — the same as changing your camera's exposure by a fraction of a stop. At +100 the image gets one full stop brighter. At -100, one full stop darker. This is the most physically accurate way to adjust overall brightness.
Use Exposure for global brightness corrections. Use Brightness for midtone adjustments without moving the blacks or whites.
Applies a gamma curve (pow(v, 1/gamma)) rather than a flat additive shift. This lifts or lowers the midtones while keeping pure black at 0 and pure white at 1. At +100, the gamma is 0.4 — a strong midtone lift. At -100, the gamma is 2.5 — a significant midtone drop.
The key difference from Exposure: Brightness doesn't move your shadow floor or blow out your highlights.
An S-curve pivoted at the average luminance of your image — computed when the image loads. This means the contrast pivot is centred to your specific photo, not a fixed 50% grey. At +100 the factor is 2.0 — values above the pivot get brighter, values below get darker.
Both operate on luminance, not individual channels. This is important — applying tonal adjustments per-channel would shift the hue of partially-lit areas. By computing the pixel's luminance first and applying a uniform multiplier to all three channels, the hue is preserved.
The tonal boundary sits at 0.22 in linear light, which corresponds to roughly perceptual 50% grey. Highlights affects pixels above this boundary; Shadows affects pixels below it. Both use a smoothstep curve so the transition is gradual.
Whites applies a sigmoid compression curve anchored above v=0.5 in linear light. Positive values pull bright pixels away from clipping — useful for recovering blown-out skies. Negative values push highlights further.
Blacks applies a steep curve anchored below v=0.25. Positive values lift the shadow floor (the "faded" or "matte" look popular in film emulation). Negative values crush the blacks for deeper contrast.
Uses a 3×3 Bradford chromatic adaptation matrix rather than a simple R/B channel shift. Warming doesn't just add red — it also adjusts green slightly to mimic how incandescent light actually shifts colour along the Planckian locus. This is why extreme values feel warm rather than "digitally orange."
Adjusts the green/magenta axis orthogonally to Temperature. Used to correct for fluorescent lighting (green cast) or mixed light sources.
Rec.709 luminance-preserving saturation. Computes 0.2126R + 0.7152G + 0.0722B as the luminance, then blends each channel toward or away from that grey. At -100 the image becomes greyscale. The luminance weighting preserves perceived brightness as saturation increases.
Like Saturation, but the boost factor is modulated by pow(1 - currentSaturation, 2). Pixels that are already near fully saturated get almost no boost. Flat, dull colours get the full vibrance amount applied. This protects skin tones and vivid colours while lifting the greys and near-neutrals.
Natural/documentary look:
Moody/cinematic:
Clean and bright:
All eight presets in the Presets tab are built from combinations of these parameters. They're a starting point — the sliders give you full control from there.