At first, I tried to match the colour, but I wasn’t satisfied with the result. It was too white and too far from the source. So I decided to do it manually because I generally like to adjust colours in Photoshop. When doing colour correction, I first used the Grade node to quickly alter the gain, multiply and gamma of the plane shot. Then I tried ColorLookup, where I focused on the blue channel (to enhance the colour and match it better with the background) and the alpha channel (which helped me blend the end of the plane and add some warmth there). I adjusted almost all the channels in the HueCorrect node. Finally, I added some minor adjustments to the mid-tones and shadows in the ColorCorrect node. I still think the front part of the aircraft is too bright and doesn’t blend in with the surroundings, but patching it up with colour nodes messed up other parts of the plane, so I left it as it is.
Workshop notes:
Premultiplication:
By default, Premult multiplies the input’s rgb channels by its alpha (in other words, premultiplies the input image). You may need this node when merging unpremultiplied (without alpha) images. Because Merge nodes in Nuke expect premultiplied images, you should use this node before any Merge operations if your input images are unpremultiplied. This avoids unwanted artifacts, such as fringing around masked objects.
Colour correcting premultiplied images:
When you colour correct a premultiplied image, you should first connect an Unpremult node to the image to turn the image into an unpremultiplied one. Then, perform the colour correction. Finally, add a Premult node to return the image to its original premultiplied state for Merge operations. Typically, most 3D rendered images are premultiplied. As a rule of thumb, if the background is black or even just very dark, the image may be premultiplied.
Other:
- Reformat lets you resize and reposition your image sequences to a different format (width and height). This also allows you to use plates of varying image resolution on a single script without running into issues when combining them.
- Merge nodes deal with layering multiple images together. The default mode is over, which simply places one image on top of another. You can choose from a variety of operations that change how merged layers interact.
- Keymix (all) is similar to Merge but accepts unpremult assets. Often used for merging masks.
- The ColorCorrect node is used to make quick adjustments to contrast, gamma, gain, and offset. You can apply these to a clip’s master (entire tonal range), shadows, midtones, or highlights. You can control the range of the image that is considered to be in the shadows, midtones, and highlights using the lookup curves on the Ranges tab. However, do not adjust the midtone curve – midtones are always equal to 1 minus the other two curves. You can also create this node by pressing C on the Node Graph.
Colorspace and Linearization:
Colorspace defines how the footage was captured or exported. Most files are non-linear, and knowing the correct colorspace is critical for proper linearization.
Linearization is the process of converting footage into linear space. All the tools inside nuke are built around linear math. This also allows the mixing of media types. We need to know what colorspace of the file was before starting to work on the file!
You can work in LOG/RAW or Linear.
LUTs, CDLs, and Grades:
- LUTs can be used for creatively or technically, i.e. converting from log to lin, or adding a “look”.
- CDLs are creative, i.e. adding a “look” to a clip.
- Graded footage means colored to it’s “final” look.
Two most commonly used nodes are Grade and ColorCorrect. Both gives us the chance to grade H, M, S of the shot. In the Nuke to grade highlights we use either gain or multiply. For shadows we use lift and to grade, midtones we use gamma. In the ColorCorrect the lift is called offset.
White-balancing in the Nuke (can be useful at times to white balance an asset before grade it to match the backgroung):
- Push all the way up the gain in the viewer and use the eyedrop in the Grade Node to select the darkest point in the images.
- Push the gain in the viewer low and select with the eyedrop from grade node the bright/white point.
- Match luminosity by manipulating multiply in the Grade Node.
- Exposure adjust in stops!