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RH MidControl

Dr Senthil Manikandan edited this page Feb 1, 2026 · 1 revision

RH MidControl

⚖️ Dynamic Contrast & Exposure Engine

RH MidControl is a precision exposure and contrast tool designed to give you granular control over your image's tonal response. Unlike standard lift/gamma/gain, it works by pivoting around a user-definable Mid Point, allowing you to stretch or compress shadows and highlights independently with varied curve behaviors.


📖 Table of Contents


1. Core Concept 💡

The heart of this tool is the Mid Point. Standard contrast expands from a fixed grey point (often 0.18 or 0.5). RH MidControl allows you to dynamicly set where that pivot distinction lies.

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Image Showing the Highlighted IRE on the viewer

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  • Shadows Curve operates on everything below the Mid Point.
  • Highlights Curve operates on everything above the Mid Point.

This decoupling allows for asymmetric contrast adjustments (e.g., crushing shadows while leaving highlights linear, or boosting highlights while lifting shadows).


2. Global Controls 🌐

Primary adjustments for defining the tonal range.

Mid Point ⚖️

Screenshot 2026-02-02 032608

Sets the pivot limit (in IRE 0-100) between Shadows and Highlights.

  • Default: 50.0 (Middle Grey)
  • Moving this slider changes which parts of the image are affected by the Low/High Exposure controls.

Shadows Curve 📉 | Highlights Curve 📈

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Controls the exposure/density of the respective regions.

  • Range: +/- 200.0
  • Negative Values: Darken/Compress the region.
  • Positive Values: Brighten/Lift the region.

3. Levels & Curve Types 🎛️

Levels Controls

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  • Black Point ◾: Sets the absolute black level floor.
  • White Point ◽: Sets the absolute white level ceiling. Use these to expand or contract the global dynamic range after curve adjustments.

Curve Types

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You can select different mathematical curves for how the Shadow and Highlight adjustments are applied.

Curve Type Description Feel
Hermite Quadratic Ease-Out Gentle. Smooth, natural rolloff. Good for subtle adjustments.
Sine Sine Ease-Out Strong. Harmonic lift. More aggressive than Hermite but still organic.
Quadratic Cubic Ease-Out Intense. Very sharp falloff. Good for heavy styling or creative effects.

4. Vector Controls (RGB) 🔴🟢🔵

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Independently adjust the strength of the curve effect on specific color channels.

  • Controls: Red, Green, Blue (Separated for Low/Shadows and High/Highlights).
  • Range: -1.0 to 1.0.
    • 0.0: Default (follows Luma).
    • 1.0: Increases the effect on this channel.
    • -1.0: Decreases the effect on this channel.

Usage Tip: Push the Blue Shadows up to create cool, dense shadows, or reduce Red Highlights to keep skin tones natural while boosting global highlights.


5. Visual Aids 👁️

Show Mid Selection 🎯

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Highlights the pixels that fall exactly at your selected Mid Point (with a small tolerance).

  • Green Pixels: Represent the exact pivot area.
  • Use this to precisely target a specific zone (e.g., placing the pivot exactly on skin tone brightness). 1

Show Curves 📊

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Overlays a graph showing the Input vs Output transfer function.

  • White Line: Luma Response.
  • Red/Green/Blue Lines: Individual Channel Responses.
  • Use this to potential clipping or to understand the shape of the selected Curve Type (Hermite vs Sine vs Quadratic).

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