What you will learn
- over = A + B·(1−α), and A must already be premultiplied
- Glowing rim = premult missing · dark rim = premult twice
- Anything that is not a pure multiply (lift, gamma) goes unpremult → grade → premult
- Horizon = camera eye level; use objects of known height as rulers
- Tilt moves the horizon; camera height changes how deep the ground looks
- If the horizons agree but CG still floats, check camera height next, then match the real focal length
- Black is a colour per depth zone; far blacks are lifted and tinted by haze
- Lift blacks with a toe that only touches the darks, not Grade lift on HDR
- Check with the viewer gamma/gain up and down, not by eye alone
Preview: one question (no sign-up)
An orange shape merged over sky three ways. Which one is premultiplied correctly?
Syllabus
The first 3 lessons are free and fully working. The rest belong to the full courses, and each one says honestly how far along it is.
Edges and alpha4 lessons
Camera and space2 lessons
Colour and air3 lessons
AI in comp1 lessons
Progress is kept on this device only; there are no accounts yet.
Common misunderstandings
A key is a mask, so more contrast is always better?
Truth: Crushing a key to pure black and white eats soft edges like hair and motion blur. Keep a soft key for the edge, a separate hard core key inside, and combine them with max.
Screen is the best way to add light?
Truth: Nuke’s screen gives A+B−AB only when values are ≤ 1; above 1 it returns max(A,B), which clips HDR. For light, use plus.
Matching blacks = raising lift in a Grade?
Truth: Grade lift pivots at 1, so it also pulls highlights down (lift 0.1 turns 4.5 into 4.15). Use a toe that only touches the darks.
Add grain to every element along the way?
Truth: Grain goes on once, as the last node, per channel, blacks first; blue is usually the strongest.
Any grade works fine on a premultiplied image?
Truth: Only pure multiplies are safe on premultiplied images. Lift, gamma and offset need unpremult → grade → premult, or the edges go wrong.
CG needs pure black to look punchy?
Truth: Almost nothing in a real plate reaches 0. CG blacks follow depth: far things sit in haze, so their black is lifted and tinted.
How it works
- Try firstAnswer one real question or move a slider. No sign-up.
- See whyEvery answer tells you why, not just right or wrong, with a picture you can move next to it.
- The next one is waitingEach lesson ends with a "what you learned" card and the lesson worth doing next.
Sky · VFX compositor (Nuke, Blender)
Space for Sky’s real credits. Left empty on purpose; Sky fills it in.
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