User Guide - Film Density Curves
Film Density vs Saturation
Before we dive into the film density tools in 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.
Film 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 film 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.
Density Curve
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.
Chroma Curve
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 curve, 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, accurately models the non-linear saturation response of analog film.
Saturation Curve
The Saturation vs Luminance curve in Color.io allows you to adjust the saturation 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.
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. Unlike the density and chrominance curves, this curve uses a standard saturation algorithm without additional luminance weighting.
Keyboard Shortcuts: Hold down the CMD (Mac) or CTRL (Win) Key while dragging to lock a curve point to its current hue value and only affect its color density amount. As with all other tools, double click a point to reset it back to its default position.
With Color.io you can edit images and build 3D LUTs with a powerful online raw developer and analog film look designer for photographers and filmmakers. Craft stunning film color in record time that works for any camera, in any software and on any device, directly in your browser.
