Color.io User Guide | Tools

Color.io allows you to create looks that are consistent across a wide range of cameras and output devices like monitors and projectors. Color.io is powered by ACES, the Academy Color Encoding System. ACES is a color management system that provides a consistent and reliable way to work with color in the film and visual effects industries.

ACES includes two key workflow components: Input Device Transforms (IDTs) and Output Device Transforms (ODTs). An ACES IDT is a mathematical transform that maps the colors from a specific camera, into the ACES color space. An ACES ODT is a mathematical transform that maps the colors from the ACES color space into the color space of a specific output device, such as a display or projector.

Choose an ACES IDT for your camera by clicking on the camera icon at the top right of the viewport. If your specific camera is not listed, go with the appropriate generic color space such as sRGB, Rec709, AdobeRGB, ProPhotoRGB or VisionLog. Repeat the same for your desired output by clicking on the monitor icon next to the camera icon and choosing an appropriate output color space. The default for both input and output is sRGB.

RAW Development: For RAW Image development it is recommended to always choose the VisionLog IDT. The RAW processor built into color.io debayers and interprets RAW camera data as VisionLog and you will get consistently predictable results by choosing VisionLog for all supported RAW camera inputs.

Spatial Volume

The Spatial Volume tool in color.io offers a convenient way to change color density and luminance distribution of an image in a single XY control. Dragging the point across the X-Axis changes color density. Color density is similar to saturation or vibrance in traditional color grading terminology and determines the intensity of colors. The density model used by color.io however uses non-linear retainers and stabilizers that create a film-like saturation response. Dragging the point all the way to the left will fully desaturate the image and create a black and white base. Dragging it all the way to the right will give colors a density boost without blowing out color channels like traditional saturation controls.

Dragging the point across the Y-Axis shifts the luminance distribution around and is a convenient way to softly brighten up the shadows or darken the highlights of an image. Similar to the density control, the response behaviour of this control is highly non-linear and protects both shadows and highlights from clipping.

Spectral Balance

Spectral balance combines color temperature and color tint distribution in a convenient XY tool. The ranges for both color temperature and tint are mapped to physical film response curves so the parameters do not correspond 1:1 to traditional kelvin based metrics.

Shortcuts: Like most tools in color.io you can restrict drag direction to the X-Axis by holding down the shift key on your keyboard while dragging a point. Hold down the CMD key (Mac) or CTRL key (Win) to restrict movement to the Y-Axis. Double click a point to reset it to its origin.

Shadow and Highlight Scattering

Light scattering plays a significant role in determining the colors that we perceive in the physical world. It influences the way light interacts with different materials and environments, and ultimately affects the way that we see colors and their intensity, saturation, and hue. The specific physical effect responsible for ambient color tints in the physical world is a combination of the Tyndall Effect and Rayleigh Scattering after which the response behaviour of the scattering wheels are modelled.

Use the shadow scattering wheel to add ambient color to the shadows of an image. Unlike traditional color wheels, scattering holds on to the naturally occurring shadow colors in an image longer and tints dark pixels in a way that is consistent with light behaviour in the physical world.

Highlight scattering works similarly although instead of protecting color purity, the algorithmic color model is optimized to prevent highlight spill over into the lower luminance range of the image which is typical of traditional lift gamma gain controls.

Pro Tip: Use both wheels in combination to create powerful color contrasts and film tint emulations. Most motion picture film stocks have slightly cool shadows and slightly warm highlights: Try to move the shadow point to the lower left and the highlight point in the opposite direction to the upper right. Don't forget to mention us in your Academy Award acceptance speech.

Shadow and Highlight Refraction

The Color Refraction tool in the color.io app allows you to make advanced color adjustments to your images by controlling the hue and density of colors in the shadow and highlight regions. Refraction uses an algorithmic transform model that offers much higher color mapping and density stability than other models like HSL or HSV while providing the same intuitive interface.

The Shadow and Highlight Refraction Wheels offer 6 color points for red, yellow, green, cyan, blue, and magenta hue vectors. You can adjust the hue of each point by moving it in an orbital motion, and desaturate or increase the color density by moving the point toward the center or outer boundary of the circle, respectively.

Keyboard Shortcuts: Hold down the Shift Key while dragging to lock a point to its current orbit for hue adjustments. Hold down the CMD (Mac) or CTRL (Win) Key to lock a point to its current angle for density adjustments.

By default, the Shadow and Highlight Refraction Wheels are synchronized, which means that any mappings are applied to the entire luminance range of the color space. However, you can detach the wheels and make separate refraction adjustments for shadows and highlights by clicking on the link icon between the wheels. The split point between shadows and highlights can be adjusted with the number input below the link icon, and a mask preview of the split point can be toggled by clicking the mask button below the number input. Whatever part of the mask image is black will be affected by the shadow refraction settings, while everything that is white will be affected by the highlight refraction settings.

The Color Refraction tool in color.io provides advanced and film-like color compression and expansion capabilities, with built-in film density and the option to make separate adjustments in the shadow and highlight regions for fine grained color control over the final image.

Insider Knowledge: By moving color points closer to each other, you can perform a hue-compression of colors, while spreading them out increases color contrast. Color compression is an important aspect of film response modelling, just like allowing slightly less color density in the highlights than the shadows.

Before we dive into the Density tools of Color.io and explain what they do, let us first define saturation: Saturation is a straightforward measure of the intensity of colors in an image, with higher saturation meaning more intense and vivid colors and lower saturation meaning more muted and desaturated colors. When you adjust saturation in most photo editing or color grading tools, all colors are affected equally, regardless of their original intensity. This can often lead to over-saturation and loss of detail in bright colors, just like in the right part of the example image above.

Density, on the other hand, is a more sophisticated model for adjusting the intensity of colors in an image. Instead of affecting all colors equally, density selectively increases the intensity of colors that are less saturated, while leaving colors that are already saturated relatively unchanged. While that sounds like what Vibrance was probably designed to do, Color.io uses additional non-linear gamut retainers to selectively avoid over-saturating bright colors by applying film-derived luminance weights to the horizontally expanding gamut.

The complex interplay of selective saturation, gamut compression and film-derived luminance weighting is what we refer to as Density in Color.io. It is an algorithmic model for emulating film density and a major contributor to the rich, painterly colors and  natural-looking images you can create with Color.io.

The Hue vs Density Bezier Curve in Color.io is allows you to adjust the color density of individual hue vectors of an image. Unlike traditional saturation controls that simply increase or decrease the intensity of all colors equally, the Bezier Curve allows you to make film-like density adjustments to individual hues.

The curve uses a non-standard bezier algorithm that automatically distributes the points in a way that maximizes color smoothness, making it easier to achieve natural-looking results without having to design every aspect of the curve yourself. To use the Bezier Curve, simply click on a point and drag it to adjust its position. Hue vs Density is a highly advanced and versatile tool for color correction and grading. Its unique algorithm makes it possible to achieve natural-looking results and emulate the film density response in a way that is not possible with traditional saturation controls.

Keyboard 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 color density amount.

The Density vs Chrominance curve in Color.io allows you to adjust the density of colors in your image based on their chrominance values. Chrominance describes how colorful a pixel is. So what this curve allows you to do, in simple terms, is add or remove color intensity based on how much color the image has to begin with. When you push the left part of the curve up, you are increasing color intensity of unsaturated pixels, while lowering the right part of the curve will decrease color intensity of heavily saturated pixels.

Unlike the Density vs Hue cuve, this curve uses a cubic spline model to distribute points automatically, ensuring maximum color smoothness.

The curve displays the chrominance values of your image along the x-axis, spanning from roughly greyscale to fully saturated. The underlying density algorithm that is used across the color.io application, models the non-linear saturation response of analog film.

The Density vs Luminance curve in Color.io allows you to adjust the density of colors in your image based on their luminance values. In other words, what this curve allows you to do, is to add or remove color intensity based on how bright the pixels in your image are. You can use this do desaturate only the shadows or highlights of an image while leaving the midtones untouched.

Just like the Density vs Hue cuve, this curve uses a non-standard bezier spline algorithm which distributes points automatically, ensuring maximum color smoothness and great user experience.

The curve displays the luminance values of your image along the x-axis, spanning from roughly black on the left to white on the right. The underlying density algorithm that is used across the color.io application, models the non-linear saturation response of analog film.

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 the ACES IDT and ODT, 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.

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.