How To: Color Grading

Introduction

A major benefit of shooting uncompressed RAW is taking advantage of a wide gamut of color depth, allowing for subtle or drastic changes in post without the addition of artifacts or degrading the image. There are, however, differences between grading 12-bit RAW and other video files that you should know in order to make your footage appear its best.

Color Space

Grading 12-bit RAW footage from your D16 is a slightly different process than grading regular video files, because the CinemaDNG files must be displayed in the correct color space in order for the image to look normal. A “color space” is essentially a mathematical  algorithm that determines how colors in a digital image should be captured and displayed.

RGB_and_CMYK_comparison

CMYK images appear “washed out” on a computer monitor, because the image is not in the correct monitor color space.

The most common “color spaces” we encounter on a day-to-day basis are RGB, the color space used to intake and display graphics on monitors like a television or computer monitor, and CMYK, the color space used for print graphics like magazines and catalogs.

Those familiar with graphic design will have encountered the way a CMYK image looks slightly “washed out” when an image intended for print is displayed on a computer monitor—because the image is not being displayed in the monitor’s native (RGB) color space.

 

Rec709

Many color grading systems default to Rec709 color space, which is an 8-bit RGB color space meant for television broadcast. Rec709 squeezes the colors of an image into 8 bits between the white point (brightest color) and black point (darkest color), making images appear brighter and more saturated, with crushed blacks and bright highlights. Banding in subtle gradients such as a sky also occur, because the 8-bits do not contain enough color information to display the gradient smoothly.

When you open a 12-bit CinemaDNG file in an 8-bit Rec709 color space, the image appears “wrong”, just like CMYK images appear “wrong” on an RGB monitor; the color algorithm for displaying Rec709 does not match the color algorithm captured in your CinemaDNG image. The most noticeable problem with CinemaDNG footage displayed in a Rec709 color space is that it appears to have a magenta tint, which is most noticeable in bright white areas. The image is also slightly “washed out”, displaying lower contrast and less vibrancy than the recorded footage.

Compare the white sails and their reflections on the water and the overall contrast between the images below:

color-space

It is important to make sure your D16 footage is in the correct color space before you begin grading, or your images will suffer from “magenta highlights” or poor contrast.

Note: LightPost currently displays images in a Rec709 color space. If you have used LightPost to create proxy files to edit in Premiere CS6, Final Cut Pro, or Avid instead of editing natively in CinemaDNG in Premiere Pro CC, make sure to save your CinemaDNG files for color grading—software like Da Vinci Resolve and Adobe Speedgrade are able to swap your .mov proxies for CinemaDNG sequences in your coloring timeline, allowing you to utilize the correct color space, ensuring that your images will be displayed and colored properly. The correct color space in Da Vinci Resolve is called “BMD Film”; there are a number of LUTs available for download that will give you the correct look in SpeedGrade.

Topics — Color Grading on the D16

  • Lumetri Looks and LUT options for Premiere Pro CC

Tutorials — Color Grading on the D16

Da Vinci Resolve

Adobe Creative Suite