User Guide - Change Contrast and Brightness
Luminance Curve
The Luminance vs Luminance curve in Color.io is a traditional contrast curve with built-in brightness-dependent film density response. Darkening colors increases their density and brightening exhibits a subtle bleach effect. Since most contrast and saturation is determined by setting the correct input color space for the image and the correct output color space for the target display, this curve is normally used for subtle modifications.
The curve displays the luminance values of your image along the x-axis, spanning from roughly black on the left to roughly white on the right.
Good to know: Though this curve type will be familiar to those coming from Lightroom or similar applications, the interface curve in Color.io does not have a 1:1 relationship with the actual image gamma. It is more of an approximate driver of a more complex and attenuated response curve that is applied to the color space under the hood. Use the 3D LUT view as your source of truth and get an accurate visual representation of the real gamma and chroma distribution of your grade if you need a precise read-out.
Radiance Curve
Use this curve to selectively darken or brighten individual hue vectors. The curve uses the same non-standard bezier implementation as the Density vs Hue Control and is optimized for retaining maximum color smoothness.
To use the Luma vs Hue Bezier Curve, simply click on a point and drag it to adjust its position. Dragging a point up will smoothly brighten its corresponding hue section in the image. Dragging it down will make it darker.
Shortcuts: Hold down the CMD (Mac) or CTRL (Win) Key while dragging to lock a point to its current hue value and only affect its brightness. Double-click any point to reset it to its default position.
RGB Mixer
When working with either the Black Point or White Point sliders, by default, all three channels (Red, Green, and Blue) are moved in unison. This means when you adjust the Black Point, for instance, you're uniformly altering the intensity of all colors in the dark areas. Likewise, the White Point slider simultaneously adjusts all color channels in the brighter regions of your image.
If you want more granular control over the colors in your blacks and whites, you can detach the channels by clicking on the link icon below the sliders. Once decoupled, each RGB channel can be manipulated independently.
This decoupling feature allows you to infuse color into your blacks and whites. For instance, adjusting the Red channel in the Black Point slider can add a warm, reddish tone to your shadows, while manipulating the Blue channel in the White Point slider might add a cool tint to your highlights.
Different tools for split toning: While both the Black/White Point Sliders and Color Scattering Wheels can add color to your image, they serve different roles. The Scattering Wheels, vital for film emulation, shape your look by emulating light behavior and should form the base of your grading work. In contrast, the Black/White Point Sliders, which act more linearly, are ideal for final touch-ups and fine-tuning your overall color balance.
Other ways to change brightness and contrast
While the Luminance panel in Color.io is specifically dedicated to making changes to brightness and contrast to an image, there are several other tools at your disposal to directly or indirectly influence these parameters:
- Input Color Space: The input color space has a significant impact on the overall image, most notably the contrast curve. Always try to use the correct input color space for your camera or the type of image you're working with.
- Spatial Volume: This tool globally changes the shadow and highlight brightness prior to any other color transformation in the pipeline. It's meant to quickly adapt a look to an image by darkening or brightening it while protecting shadows and highlights from clipping.
- Film Density Adjustments: Since film density selectively darkens colors as they become more saturated, all of the tools in Color.io that affect film density (like Spatial Volume, Refraction and the Density curves), also indirectly change the brightness of certain colors.
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