COLOR GRADING PROCESS
In this article, I will try to explain the color grading process, definitions and the most important technical details about color grading and why it matters.
Color grading is one of the final post-production stages, during which the colors of the film are enhanced and adjusted. Having a talented colorist for your film, commercial or music video can be an absolute game-changer for your final result.
Back when movies were shot on film, color grading was called “color timing”. It referred to a process, in which the film would be exposed to a certain environmental factor in order to influence the color of the film. Nowadays, it is most often called color grading or color correction and it is done on a digital film file.
Just to clarify, in bigger post-production facilities, a lot of tasks are divided between the color grading team: online editors, assistant colorists, color technicians, colorists, etc. As we are a small post-production studio, our colorists perform a one-man show in this process. Because we are used to this workflow, we will explain these workflows as done by one person, even though, they usually are not.
There are two main steps in this process:
1. Color correction
This is the stage in which the colorist adjusts the film for it to be consistent from shot to shot. The colorist will often adjust contrast, white balance, exposure, and other settings.
Main goals of the color correction stage are:
To even out the film so it would look consistent from scene to scene.
Prepare the film for VFX if needed
To change the overall atmosphere of the scene (for example: to change a scene, which was shot during the day to a night scene, or a sunny day to a cloudy one, etc.)
Some of the main tools include:
Brightness - refers to the overall darkness or lightness of the video.
Contrast - it’s the difference in brightness between objects in the video.
White balance - to put it simply, it means adjusting the colors so that the image would look as natural as possible. Most light sources (such as a lightbulb or the sun) do not shine in purely white color and neither do they shine similarly to one another. Thus for example, if one scene was shot outside and another was shot inside with inside lighting, then the camera has to be adjusted accordingly so that the actors’ faces and objects or white color would look the same in both shots/wouldn’t differ drastically. However, due to a lot of reasons, sometimes this needs to be corrected in post-production. That is when the colorist steps in.
Exposure - refers to the amount of light being captured by the camera. Exposure is also linked to contrast and brightness.
2. Color grading
Once the film is more or less consistent from frame to frame, the colorist can start adjusting the colors to create a specific mood or look of the film. Color grading is a far more subjective process than color correction. It is important to note, that color grading needs to be done on well-calibrated professional film projector (for films) or monitor (for TV, commercial, etc.). The results can vary drastically on different displays.
Main goals of the color grading stage are:
To achieve the desired look and mood of the film
To enhance the dramatic feel of a particular scene
To increase the emotional impact on the audience through color
From Pre-Production to Post-Production
It is important to plan the post-production in pre-production. Color grading is no exception.
Usual and preferred workflow for colorist from pre-production to final deliverables:
1. Tests and LUTs are done in the pre-production stage to prepare for the shooting;
2. After editing is finalized, the colorist conforms the footage from the original material;
3. Shots for VFX are exported (usually, together with separate LUTs for every VFX shot or universal LUT for all VFX shots);
4. When VFX finishes the shots, they are put into the color grading project;
5. Color Correction is done;
6. Magic of color grading happens (usually with the participation of DoP and Director);
7. A DCP is created and watched in the cinema (technical screening);
8. Adjustments are done, additional technical screening is made, if necessary. (This part could loop for a while).
9. When everything is done and confirmed by DoP and Director, film is exported in DPX or J2C sequence (or TIFF, if the DCDM master is to be created). It is quality checked and forwarded to people, in charge of deliverables.
LUT - (look-up-table) is essentially a color preset that is applied to video footage or element. LUTs can create a stylized look, feel, or tone for an image, but there are also general utility and conversion LUTs. They can be used to change from one color space to another.
During pre-production, the colorist should prepare the shooting LUT (used for displaying shot material on the monitors on set, as well as applied on dailies for distribution or/and editorial files) especially, if certain mood or color pallet is needed.
If the colorist did not prepare the shooting LUT but you are filming with a professional camera and see quite natural colors on the monitors it most likely means that REC 709 conversion LUT is applied.
Professional cameras create LOG files which look like washed-out images. They contain a lot of compressed information but do not display colors in an expected way.
Most difficult aspects of color grading
It is difficult to color grade human skin because people are the main points of attraction in the shot. They will always be the most eye-catching object in the shot. The trees could be purple and the audience might not even notice that if the skin tones are correct. If everything else in the frame looks unnatural to the eye but the skin looks right, the eye will accept it. Thus, the colorist needs to make the skin color believable otherwise the audience will notice straight away.
Some people’s skin tone might look the same in all the shots and they reflect light quite evenly regardless of the day and of the source of light. However, other people might look very different based on the day, weather conditions, whether it was shot indoors/outdoors, of the time they were shot at, etc. And the colorist then has an enormous challenge to even out all the shots so that people watching the film wouldn't notice the difference.
Also, lighter skin complexion reflects surroundings, so the proper lighting, especially in green-screen shots, is very important. If lighting is not done properly during the shooting, the colorist will have an extremely difficult time trying to separate human skin from its surroundings and/or eradicate unnecessary tones.
Underexposed or overexposed shots lose information in the pixels and thus are hard to fix in post-production. Essentially, the color grader needs to recover these missing pixels and often it is not possible to do that entirely. Also, in underexposed or overexposed material there is not enough information for it to be flexible and available for drastic changes in color grading. The overexposed material has no information (plain white) in the brightest parts of the frame and the underexposed material gets very noisy and grainy if contrast or brightness is leveled up. It is very important to do all that is possible to shoot in proper exposition. It helps to invest in the proper camera (with as big F stops range as possible) but the proper lighting is the golden key.
I hope that this simple article will help you better understand the process of color grading.
If you would like to know more about the creative side of color grading as well as the importance of color for the story, we recommend this article.