Color Grading Explained: Camera Data, Decoding, Correction & Creative Looks

Zakaria Benkabouche

Camera Recording [00:01:14]

• Light enters the sensor through the lens.
• The motherboard transforms light into data.
• The data gets stored.
• This process is called OETF (opto-electronic transfer function).

Decoding [00:02:55]

• The process used to choose how data needs to be processed.

Image Signal [00:05:14]

• Videos are sequences of images. - 24, 30, or 60 images per second.
• Images are signals.
  • Luminance, red, green, and blue.
  • YRGB are the primaries.
• Gain: a tool with 4 signals and one control for intensity.
  • When the Y signal is lowered, the image starts disappearing.
  • If you turn off the lights, you can't see anything, even if it's there.
• Digital images work the same way.
  • When the RGB signal intensity is low, colors disappear and the image becomes black and white.
  • Increase intensity, and the image becomes more colorful.
  • RGB intensity together, without luminance, is saturation.
  • Lower the red signal and there is more green and blue, which gives cyan.
  • Red and green gives yellow, red and blue give magenta.
• RGB is used by 50% of the tools in DaVinci Resolve.
• HSL (Hue, Saturation, Luminance) [00:18:56] is the other 50%.
  • 3 signals.
  • 3 axis: the color, how colorful it is, and how bright it is, all in one interface.
  • The Matrix: one of the most precise tools for color correction.

Log Videos [00:22:31]

• Use a flat signal.
• Low contrast image prevents the signal from clipping.
• Crushed blacks and overexposed highlights happen when you shoot using a standard profile.
• Standard profiles are made to bypass color grading and output video ready to be displayed.
• Log profiles preserve the image signal.
• Dynamic of the sensor is preserved.

  

• If you're not color grading, use a standard profile.

Color Correction [00:25:01]

• Shot a raw sequence of images in a format called DNG.
• Choose the log profile now during the decoding process.
• When you shoot RAW, you can change almost everything.
• CIE (Commission Internationale de l'Éclairage) designed in 1931 to represent the colors our eyes can see.
• Humans are more sensitive to green due to evolution in nature.
• CIE represents a lot of colors.
• Rec 709 [00:31:43]: A tiny space, but our standard.
• DCI P3: With slightly more green, used in cinema projectors.
• Rec 2020: Designed for HDR videos.
• Professional displays cover 80% of it.
• Record so much data if you cannot display it.
  • Make powerful sensors and processing systems, but only display 50% of what we capture.
• More data, more to play with during color correction and color grading.
• Black Magic Cinema Camera records 12-bit footage.
  • 4,096 tonal steps per channel
  • Data for the artist working behind the screen.
• Black Magic Film Gen 1: Giant color space designed by Black Magic.
• Color Space Conversion converts Black Magic Film to Rec 709
  • Using Gamma Black Magic Design Film to Gamma 2.4
  • Gamut Black Magic Design Film Gen 1 to Rec 709 Gamut
• Encrypted Language: L, G, G (Lift, Gamma, Gain), WB (White Balance)

Color Grading [00:41:15]

• Light box organization - Putting scenes by scenes
• The process: corrections and ideas
• Pre-Clip: all changes and corrections will affect the entire group.
• Leveling and balancing like sound mixing, dealing with signals
  • Leveling directly affects the intensity of the signal.
  • Balancing affects the balance, and the intensity as well, but not uniformly.
    • Exposure is leveling.
    • Temperature and tint are balancing.
• Lift controls the bottom of the signal, Gamma controls the middle, Gain controls the top (the intensity).
• Lowering the lift while increasing the gain creates contrast.
• Isolate and balance a specific area/zone.
• Create a window to isolate a skin tone and match the clip.
• Track the movement to follow the camera.
• A color Matrix uses HSL color space.
  • Change the saturation of a specific color without affecting the others.
• HDR (High Dynamic Range)
  • Tools to cut the signals into multiple ranges from the deep shadows to the brightest highlights. -Is where you find data you need.
• Blend a layer on top to affect the entire project, clips, and scenes

  

• Add film grain, vignette, and prevent data loss using a clamp.
• Add a creative element
• Use color grading to show subject

Encoding [00:50:40]

• Everything needs to match
• Image ratio
• Frame rate
• Color space

  

• Starts decoding and now encoding
• Any mismatch will create a human failure
• Codex Choice: Apple Pro Res 4444XQ
• Heavy file for exporting again
• Great option to store and remaster in the future when display technology evolved
• H264 and H265
• Choice for social media
• Lighter than Apple Pro Res file but more limiting
• Designed for online streaming
• The bit rate will affect quality of the file
• Images could be 100 kilobytes or 1000 kilobytes

Split Toning [00:54:23]

• Technique from Kodak and Fuji Film.
• Kodak pushes the shadows to cyan and the highlights to red - opposite colors.
• Red and cyan create color contrast.
• Useful for more than SDR delivery.
• It is a futuristic technology, but not the standard.